Hantavirus Pulmonary Syndrome --- United States:
Updated Recommendations for Risk Reduction
Prepared by
James N. Mills, Ph.D.1 Amy Corneli, M.P.H.1 Joni C. Young, M.S.2 Laurel E. Garrison, M.P.H.3 Ali S. Khan, M.D.1 Thomas G. Ksiazek, D.V.M., Ph.D.1
1Division of Viral and Rickettsial Diseases
National Center for Infectious Diseases
2TRW Inc., Cleveland, OH
3Oak Ridge Institute for Science and Education, Oak Ridge, TN
The material in this report was prepared for publication by the National Center for Infectious Diseases, James M. Hughes, M.D., Director; Office of Bioterrorism
Preparedness and Response Activity, Scott Lillibridge, M.D., Director; and the National Immunization Program, Walter A. Orenstein, M.D., Director.
Summary
This report provides updated recommendations for prevention and control of hantavirus infections associated with rodents
in the United States. It supersedes the previous report (CDC. Hantavirus infection---southwestern United States:
interim recommendations for risk reduction. MMWR 1993;42[No.
RR-11]:1--13). These recommendations are based on principles
of rodent and infection control, and accumulating evidence that most infections result from exposure, in closed spaces, to
active infestations of infected rodents. The recommendations contain updated specific measures and precautions for
limiting household, recreational, and occupational exposure to rodents, eliminating rodent infestations, rodent-proofing
human dwellings, cleaning up rodent-contaminated areas and dead rodents, and working in homes of persons with
confirmed hantavirus infection or buildings with heavy rodent infestations.
Introduction
Background
In 1993, a previously unknown disease, hantavirus pulmonary syndrome (HPS), was identified among residents of
the southwestern United States (1--3). HPS was subsequently recognized throughout the contiguous United States and
the Americas. As of June 6, 2002, a total of 318 cases of HPS have been identified in 31 states, with a case fatality of 37%.*
The association of hantaviruses with rodent reservoirs warrants recommendations to minimize exposure to wild rodents.
These recommendations are based on current understanding of the epidemiologic features of hantavirus infections in the
United States.
Rodent Reservoirs of Viruses Causing HPS
All hantaviruses known to cause HPS are carried by the New World rats and mice, family Muridae,
subfamily Sigmodontinae. The subfamily Sigmodontinae contains at least 430 species of mice and rats, which are widespread in
North and South America. These wild rodents are not generally associated with urban environments as are house mice and the
black and Norway rats (all of which are in the murid subfamily Murinae). However, some species (e.g., deer mouse and
white-footed mouse) will enter human habitation in rural and suburban areas. A third group of rodents, the voles and lemmings
(family Muridae, subfamily Arvicolinae), is associated with a group of hantaviruses distinct from those that cause HPS. None of
the numerous arvicoline viruses has been associated with human disease in the United States
(4).
Several hantaviruses that are pathogenic for humans have been identified in the United States. In general, each virus has
a single primary rodent host. Other small mammals can be infected as well, but are much less likely to transmit the virus to
other animals or humans (5--7). The deer mouse
(Peromyscus maniculatus) (Figure 1) is the host for Sin Nombre virus (SNV),
the primary causative agent of HPS in the United States. The deer mouse is common and widespread in rural areas
throughout
much of the United States (Figure 2). Although prevalence varies temporally and geographically, on average
approximately 10% of deer mice tested throughout the range of the species show evidence of infection with SNV
(5).
Other hantaviruses associated with sigmodontine rodents and known to cause HPS include New York virus
(8), hosted by the white-footed mouse, Peromyscus
leucopus (Figures 3,4); Black Creek Canal virus
(9), hosted by the cotton rat, Sigmodon hispidus
(Figures 5,6); and Bayou virus (10), hosted by the rice rat,
Oryzomys palustris (Figures 7,8). Nearly all of
the continental United States falls within the range of one or more of these host species. Several other sigmodontine rodent
species in the United States are associated with additional hantaviruses that have yet to be implicated in human disease. These
species include the brush mouse, Peromyscus
boylii (11); and the Western harvest mouse,
Reithrodontomys megalotis (12). Only the
deer mouse and the white-footed mouse are commonly associated with peridomestic environments. Identifying characteristics
and natural history of all these host species are available from other sources
(13,14).
Numerous species of sigmodontine rodents also are associated with HPS in South America
(4). Several new sigmodontine hantavirus hosts have been discovered each year and more probably await discovery. Until the extent of hantavirus
infection throughout the subfamily Sigmodontinae becomes known, as does the pathogenicity of hantaviruses hosted by
sigmodontine species, treating all sigmodontines as potential hosts of HPS-causing hantaviruses, and each sigmodontine rodent as though
it were infected and infectious is recommended. For
the general public, this recommendation applies to all wild mice and
rats encountered in rural areas throughout the United States.
Other Diseases Associated with Hantavirus Infection
Because the sigmodontine rodents are restricted to the Americas, HPS is restricted to the Americas. Another group
of hantaviruses associated with murine and arvicoline rodents causes a group of diseases of varying severity referred to
as hemorrhagic fever with renal syndrome (HFRS) in Europe and Asia. Hantaan and Dobrava viruses, hosted by the murine
field mice (Apodemus agrarius and Apodemus
flavicollis, respectively), cause thousands of cases of severe HFRS each year in Asia
and Eastern Europe. Fatality associated with these infections can be as high as 10%
(15). The cosmopolitan Norway rat
(Rattus norvegicus) is host for Seoul virus, which causes a mild form of HFRS in Asia. Although evidence of infection with Seoul
virus has been found in Norway rats throughout much of the world, including the United States, human disease caused by
Seoul virus is largely restricted to Asia. Only three suspected cases have been reported in the United States
(16). Overall mortality associated with Seoul virus infection is probably <1%
(15).
Puumala virus, carried by an arvicoline rodent, the bank vole
(Clethrionomys glareolus), causes a mild form of HFRS,
referred to as nephropathia epidemica (NE). NE, which is very common in northern Europe, has a case fatality of <1%. Several
other species of arvicoline rodents host hantaviruses in the northern hemisphere, including the United States; none of these
have been associated with any human disease.
Infection in the Host
Hantaviruses do not cause overt illness in their reservoir hosts
(17). Although infected rodents shed virus in saliva, urine,
and feces for many weeks, months, or for life, the quantity of virus shed can be much greater approximately 3--8 weeks
after infection (18). The demonstrated presence of infectious virus in saliva of infected rodents and the marked sensitivity of
these animals to hantaviruses following intramuscular inoculation suggest that biting might be an important mode of
transmission from rodent to rodent (18,19). Field data suggest that transmission in host populations occurs horizontally, more
frequently among male rodents, and might be associated with fighting,
particularly, but not exclusively, among males
(7,20).
Occasional evidence of infection (antibody) is found in numerous other species of rodents and their predators (e.g.,
dogs, cats, and coyotes), indicating that many (perhaps any) mammal species coming into contact with an infected host
might become infected (21). No evidence supports the transmission of infection to other animals or to humans from these
"dead-end" hosts. However, domestic animals (e.g., cats and dogs) might bring infected rodents into contact with
humans. Arthropod vectors are not known to have a role in the transmission of hantaviruses
(17,22).
The reservoir hosts of the hantaviruses in the western United States also act as hosts for the bacterium
Yersinia pestis, the etiologic agent of plague. Although no evidence exists that fleas and other ectoparasites play a role in hantavirus
epidemiology, rodent fleas transmit plague. Species of
Peromyscus are susceptible to Y. pestis
infection and can act as hosts for infected
fleas. Control of rodents without concurrent control of fleas might therefore increase the risk of human plague as the rodent
fleas seek an alternative food source.
Transmission to Humans
The Old World hantaviruses causing HFRS, and the New World agents of HPS are believed to be transmitted by the
same mechanisms. Human infection occurs most commonly through the inhalation of infectious, aerosolized saliva or
excreta. Persons visiting laboratories where infected rodents were housed have been infected after only a few minutes of exposure
to animal holding areas (22). Transmission can occur when dried materials contaminated by rodent excreta are disturbed
and inhaled, directly introduced into broken skin or conjunctivae, or possibly, when ingested in contaminated food or
water. Persons have also acquired HFRS and HPS after being
bitten by rodents (23,24). High risk of exposure has been associated
with entering or cleaning rodent-infested structures
(25).
Person-to-person transmission has not been associated with any of the Old World hantaviruses
(26) or with HPS cases in the United States
(27). However, person-to-person transmission, including nosocomial transmission of Andes virus, was
well documented for a single outbreak in southern Argentina
(28,29) and suspected to have occurred much less extensively
in another outbreak in Chile associated with the same virus
(30).
Epidemiology
Hantavirus infections are associated with domestic, occupational, or recreational activities that bring humans into
contact with infected rodents, usually in rural settings. Known hantavirus infections of humans occur primarily in adults. HPS cases
in the United States occur throughout the year, but greater numbers are reported in spring and summer. Hantavirus
infection (resulting in HPS or HFRS) has been epidemiologically associated with the following situations
(25,31--36):
increasing numbers of host rodents in human dwellings;
occupying or cleaning previously vacant cabins or other dwellings that are actively infested with rodents;
cleaning barns and other outbuildings;
disturbing excreta or rodent nests around the home or workplace;
residing in or visiting areas where substantial increases have occurred in numbers of host rodents or numbers of
hantavirus-infected host rodents;
handling mice without gloves;
keeping captive wild rodents as pets or research subjects;
handling equipment or machinery that
has been in storage;
disturbing excreta in rodent-infested areas while hiking or camping;
sleeping on the ground; and
hand plowing or planting.
However, in North America, the absolute risk of hantavirus infection to the general public is low; only 20--50 cases of
HPS have been confirmed annually in the United States since the disease was described in 1993 (Figure 2).
Physical Properties of Hantaviruses
Hantaviruses have lipid envelopes that are susceptible to most disinfectants (e.g., dilute chlorine solutions, detergents,
or most general-purpose household disinfectants)
(37). Depending on environmental conditions, these viruses probably
survive <1 week in indoor environments and much shorter periods (perhaps hours) when exposed to sunlight outdoors
(38).
Prevention
Eradicating the reservoir hosts of hantaviruses is neither feasible nor desirable because of the wide distribution
of sigmodontine rodents in North America and their importance in the function of natural ecosystems. The best
currently available approach for disease control and prevention is risk reduction through environmental modification and
hygiene practices that deter rodents from colonizing the home and work environment, as well as safe cleanup of rodent waste
and nesting materials. Controlled experiments have demonstrated that simple and inexpensive methods are effective in
preventing rodents from entering rural dwellings
(39).
These recommendations emphasize the prevention of HPS associated with sigmodontine rodents in the Americas.
Although the risk of acquiring hantavirus disease from contact with native arvicoline rodents in North America or introduced
murine rodents throughout the Americas is low, the true pathogenicity for humans of all hantaviruses carried by these groups
of
rodents has not been established. Therefore, we recommend that persons avoid contact with all wild and peridomestic rats
and mice. The precautions described in this report are broadly applicable to all groups of rats and mice.
Precautions To Limit Household Exposure to Rodents
Rodent control in and around the home remains the primary strategy in preventing hantavirus infection. Rodent
infestation can be determined by direct observation of animals, or inferred by observation of their nests or feces on floors or in
protected areas (e.g., closets, kitchen cabinets, drawers, wall voids, furnace and hot water heating cabinets, and behind
ventilation screens), or from evidence that rodents have been gnawing on food or other objects. The interior and exterior of the
home should be carefully inspected at least twice per year for any openings where rodents could enter the home and for
conditions that could support rodent activity. If any evidence of rodent infestation is detected inside the home or in
outbuildings, precautions should be taken. The guidelines in the section Special Precautions for Homes of Persons with
Confirmed Hantavirus Infection or Buildings with Heavy Rodent Infestations should be followed if a structure is associated with
a confirmed case of hantavirus disease or if evidence of heavy rodent infestation is present (e.g., piles of feces or numerous
nests or dead rodents).
Recommendations are listed below for 1) reducing rodent shelter and food sources inside and outside the home and
2) preventing rodents from entering the home by
rodent-proofing (40--42).
Reduction of Rodent Shelter and Food Sources Inside and Outside the Home
Precautions for Inside the Home
Keep food and water covered and stored in rodent-proof
containers.†
Keep pet food covered and stored in rodent-proof containers. Allow pets only enough food for each meal, then store
or discard any remaining food. Do not leave excess pet food or water out overnight.
If storing trash and food waste inside the home, do so in rodent-proof containers, and frequently clean the interiors
and exteriors of the containers with soap and water.
Wash dishes, pans, and cooking utensils immediately after use.
Remove leftover food and clean up all spilled food from cooking and eating areas.
Do not store empty aluminum cans or other opened containers with food residues inside the home.
Dispose of trash and garbage on a frequent and regular basis, and pick up or eliminate clutter.
Keep items (e.g., boxes, clothes, and blankets) off of the floor to prevent rodents from nesting in them.
Repair water leaks and prevent condensation from forming on cold water pipes by insulating them. Deny rodents access
to moisture (e.g., mop closets, boiler rooms, catch basins under potted plants, and areas around aquarium tanks). Correct
any conditions that support the growth of mold, mildew, or other fungi in the home.
Keep exterior doors and windows closed unless protected by tight-fitting screens.
Use spring-loaded
traps§ in the home. Use a small amount (the size of a pea) of chunky peanut butter as bait. Place the
trap perpendicular to the baseboard or wall surface, with the end of the trap containing the bait closest to the baseboard or
wall. Place traps in areas where rodents might be entering the home. Spring-loaded traps can be painful or even dangerous
if they close on fingers; they should be handled with caution, and careful consideration should be given to keep children
and pets away from areas where traps are placed.
In the western United States (west of the 100th meridian, a line from mid-Texas through mid-North Dakota), a risk
of plague transmission to humans from fleas exists. Use insect repellent (containing N,N-diethyl-m-toluamide [DEET])
on clothing, shoes, and hands to reduce the risk of fleabites when picking up dead rodents and traps. In cases of heavy
rodent infestation in indoor spaces in the western United States, use an insecticide before trapping. Contact your local or state
health department to find out if plague is a danger in the area and for additional advice on appropriate flea-control methods.
Continue trapping for at least 1 additional week after the last rodent is caught. As a precaution against reinfestation,
use several baited, spring-loaded traps inside the house at all times in locations where rodents are most likely to be found.
Examine traps regularly. To dispose of traps or trapped animals, wear rubber, latex, vinyl, or nitrile gloves. Spray the
dead rodent with a disinfectant or chlorine
solution.¶ After soaking the rodent thoroughly, either take it out of the trap by
lifting the spring-loaded metal bar and letting the animal fall into a plastic bag or place the entire trap containing the dead
rodent
in a plastic bag and seal the bag. Then place the rodent into a second plastic bag and seal it. Dispose of the rodent in
the double bag by 1) burying it in a 2- to 3-foot-deep hole or 2) burning it or 3) placing it in a covered trash can that
is regularly emptied. Contact the state or local health department concerning other appropriate disposal methods.**
If the trap will be reused, decontaminate it by immersing and washing it in a disinfectant or chlorine solution and
rinsing afterward.
For substantially severe or persistent infestations, contact a pest-control professional for rodent eradication or a
building contractor for rodent exclusion (rodent-proofing).
When resident mice are removed from rural buildings without measures to prevent reentry, they are replaced
almost immediately by other mice from the outside. Therefore, indoor rodent-trapping could be unsuccessful in reducing
rodent infestations without simultaneous efforts to rodent-proof permeable dwellings.
Precautions for Outside the Home
Place woodpiles and stacks of lumber, bricks, stones, or other materials
>100 feet from the house.
Store grains and animal feed in rodent-proof containers.
Remove, from the vicinity of buildings, any food sources that might attract rodents.
Keep pet food covered and stored in rodent-proof containers. Allow outside pets only enough food for each meal, then store
or discard any remaining food from feeding dishes.
Avoid using bird feeders near the home. If they must be placed near the home, use "squirrel-proof" feeders and clean
up spilled seeds each evening.
Dispose of garbage and trash in rodent-proof containers with tight-fitting lids.
Haul away trash, abandoned vehicles, discarded tires, and other items that might serve as rodent nesting sites.
Mow grass closely, and cut or remove brush and dense shrubbery to a distance of at least 100 feet from the home. Trim
the limbs off any trees or shrubs that overhang or touch the building.
Use raised cement foundations in new construction of sheds, barns, and outbuildings.
Place spring-loaded traps in outbuildings (regardless of their distance from the home) and in areas that might likely
serve as rodent shelter, within 100 feet around the home; use these traps continuously, replacing the bait periodically.
For instructions concerning the safe use and cleaning of spring-loaded traps and the disposal of trapped rodents,
see Precautions for Inside the Home.**
Preventing Rodents from Entering the Home by Rodent-Proofing
Look for and seal up all gaps and holes inside and outside the home that are
>¼ -inch (>6 mm) in diameter. Inside
the home, look for and seal up all gaps and holes underneath, behind, and inside kitchen cabinets; inside closets; around
floor air vents and dryer vents; around the fireplace; around windows and doors; behind appliances (e.g., dishwashers,
clothes washers, and stoves); around pipes under the kitchen and bathroom sinks; around all
electrical, water, gas, and sewer lines (chases); and beneath or behind hot water heaters, radiators, and furnaces and around their pipes that enter the
home. Outside the home, look for and seal up all gaps and holes around windows and doors; between the foundation of
the home and the ground; under doors without weatherstripping; around electrical, water, gas, and sewer lines (chases);
and around the roof, eaves, gables, and soffits. In addition, look for unscreened attic vents and crawlspace vents. In
trailers, look for and seal up holes and gaps in the skirting, between the trim and metal siding, around utility lines and pipes
and ducts, around roof vents, and around the trailer tongue.
Seal all entry holes >¼-inch
(>6 mm) in diameter that are inside and outside the home with any of the following:
cement, lath screen or lath
metal,†† wire screening, hardware cloth (<¼-inch grate size), or other patching materials
(42). Steel wool or
STUF-FIT§§ also can be used, but caulk must be placed around the steel wool or STUF-FIT to prevent rodents
from pushing it through the hole. Caulk and expanding foam can be used to reinforce any repairs
where lath metal, hardware cloth, steel wool, or STUF-FIT are the primary materials; however, caulk or expanding foam alone are usually not
sufficient to prevent rodent intrusion.
If rodent burrows are found under foundations or trailer skirtings, construct a barrier around the entire foundation
using 14-inch wide (35 cm), <¼-inch
(<6 mm) mesh, 16--19 gauge hardware cloth. Bend the hardware cloth lengthwise into
a
right angle with two sides of approximately 7 inches (18 cm). Secure one side of the hardware cloth tightly to the
building siding. The other side should be buried at least 2 inches (5 cm) below ground level and extend out away from the
wall.¶¶
Consult a pest-control professional for severe or persistent infestations.
Precautions To Limit Occupational and Recreational Exposure to Rodents
Precautions for Workers Frequently Exposed to Rodents
Persons who frequently handle or are exposed to wild rodents are probably at higher risk for hantavirus infection than
the general public because of the frequency of their exposures. Such persons include, but are not limited to, mammalogists,
pest-control workers, some farm and domestic workers, and building and fire inspectors. Therefore, enhanced precautions
are warranted to protect them against hantavirus infection, as described below.
Workers in potentially high-risk settings should be informed by their employers about hantavirus transmission
and symptoms of infection and be given detailed guidance on prevention measures. Determining the level of risk for HPS
in each work setting is the responsibility of the employer.***
Employers should provide a comprehensive medical screening and surveillance program to workers, including
medical clearance for respirator use, baseline evaluation, and periodic examination as indicated. The physician responsible for
the program should be familiar with methods used for screening and early detection of infection in high-risk populations,
as well as with the physical demands of the job and the medical requirements for use of personal protective equipment.
On-call medical services should be provided, and workers should be able to
contact these services for 45 days after the last potential exposure.
Workers who develop a febrile or respiratory illness within 45 days of the last potential exposure should immediately
seek medical attention and inform the attending physician of the potential occupational risk of hantavirus infection.
The physician should contact local public health authorities promptly if hantavirus-associated illness is suspected. A blood
sample should be obtained and forwarded to the state health department for hantavirus antibody testing.
When removing rodents from traps or handling rodents, workers should wear either a half-face, tight-seal,
negative-pressure respirator or a (positive pressure) PAPR (powered air-purifying respirator), equipped with N-100 or P-100
filters (formerly designated high-efficiency particulate air filters [HEPA]). Negative-pressure respirators are
not protective if facial hair interferes with the face-piece to face seal
because a proper fit cannot be assured. Respirator
use practices in an occupational setting should be in accordance with Occupational Safety and Health Administration (OSHA) regulation
29 CFR 1910.134, which includes a written program specific to respirator use, risk assessment for personal
protective equipment, medical clearance to wear respiratory protection, and annual training and fit testing in each
approved respirator type (43). The comprehensive user program should be supervised by a knowledgeable person
(44). Given the predictable nature of HPS risk in certain professions or
environmental situations, provisions should be made in advance
for respiratory protection. Because of the expense associated with purchasing a PAPR system, a negative-pressure
tight-seal respirator equipped with N-100 or P-100 filters is recommended when respiratory protection is required for home
use. Respirators might cause stress to persons with respiratory or cardiac conditions; these persons should be medically
cleared before using such a respirator. Home or other users with potentially impaired respiratory function also should be aware
of the risks associated with the use of negative-pressure respirators
(43).
Workers should wear rubber, latex, vinyl, or nitrile gloves when handling rodents or handling traps containing
rodents. Before removing the gloves, wash gloved hands in a disinfectant or chlorine solution and then wash bare hands in soap
and water.**
Mammalogists, wildlife biologists, or public health personnel who handle wild rodents for research or
management purposes should refer to published safety guidelines
(45,46). Precautions are also available on CDC's website, All
About Hantaviruses (http://www.cdc.gov/ncidod/dvrd/spb/mnpages/rodentmanual.htm).
Precautions for Other Occupational Groups Having Potential Contact with Rodents
Insufficient information is available to provide general recommendations regarding risks and precautions for persons
who work in occupations with unpredictable or incidental contact with rodents or their nesting sites. Examples of such
occupations include telephone installers, maintenance workers, plumbers, electricians, and certain construction workers. Workers in
these
jobs might have to enter buildings, crawl spaces, or other sites that are potentially rodent-infested, and HPS has been
reported among these workers. Recommendations for such circumstances must be made on a case-by-case basis after the
specific working environment has been assessed and state or local health and labor officials or trade unions and management,
as appropriate, have been consulted. Determining the level of risk present and implementing appropriate protective measures
is the employer's responsibility.***
Precautions for Campers and Hikers
No evidence exists to suggest that travel should be restricted in areas where HPS cases have occurred. The majority of
typical tourist activities are associated with limited or no risk that travelers will be exposed to rodents or their excreta.
However, persons engaged in outdoor activities (e.g., camping or hiking) should
take precautions to reduce the likelihood of exposure
to potentially infectious materials by following these recommendations.
Avoid touching live or dead rodents or disturbing rodent burrows, dens, or nests.
Do not use cabins or other enclosed shelters that are potentially rodent-infested until they have been appropriately
cleaned and disinfected. (See Precautions for Cleanup of Rodent-Contaminated Areas and Dead Rodents.) Rodent-proofing
might be necessary to prevent reinfestation. (See Precautions to Limit Household Exposure to Rodents.)
When an unoccupied cabin or other structure to be used has been closed for several weeks, ventilate the structure
by opening doors and windows for at least 30 minutes before occupying. Use cross ventilation if possible. Leave the
area (preferably remaining upwind) during the airing-out period. The airing helps to remove infectious primary aerosols
that might be created when hantavirus-infected rodents urinate.
Do not pitch tents or place sleeping bags in proximity to rodent feces or burrows or near possible rodent shelters
(e.g., garbage dumps or woodpiles).
Avoid sleeping on the bare ground. Use a cot with the sleeping surface at least 12 inches above the ground or use a
tent with a floor.
Keep food in rodent-proof containers.
Dispose of all trash and garbage promptly in accordance with campsite regulations by
--- burning or burying,
--- discarding in rodent-proof trash containers, or
--- "packing out" in rodent-proof containers.
Precautions for Cleanup of Rodent-Contaminated Areas and Dead Rodents
Areas with evidence of rodent activity (e.g., dead rodents and rodent excreta) should be thoroughly cleaned to reduce
the likelihood of exposure to hantavirus-infected materials. Cleanup procedures must be performed in a manner that limits
the potential for dirt or dust from contaminated surfaces to become airborne. Recommendations are listed in this report
for cleaning up 1) rodent urine and droppings, and surfaces potentially contaminated by rodents and 2) dead rodents and
rodent nests.
Cleanup of Rodent Urine and Droppings and Contaminated Surfaces
During cleaning, wear rubber, latex, vinyl, or nitrile gloves.
Spray rodent urine and droppings with a disinfectant or chlorine solution until thoroughly soaked. (See Cleanup of
Dead Rodents and Rodent Nests.)
To avoid generating potentially infectious aerosols, do not vacuum or sweep rodent urine, droppings, or
contaminated surfaces until they have been disinfected.
Use a paper towel to pick up the urine and droppings. Place the paper towel in the garbage.
After the rodent droppings and urine have been removed, disinfect items that might have been contaminated by rodents
or their urine and droppings.
--- Mop floors with a disinfectant or chlorine solution.
--- Disinfect countertops, cabinets, drawers, and other
durable surfaces with a disinfectant or chlorine solution.
--- Spray dirt floors with a disinfectant or chlorine solution.
--- Disinfect carpets with a disinfectant or with a commercial-grade steam cleaner or shampoo.
--- Steam-clean or shampoo rugs and upholstered furniture.
--- Launder potentially contaminated bedding and clothing with hot water and detergent. Use rubber, latex, vinyl,
or nitrile gloves when handling contaminated laundry. Machine-dry laundry on a high setting or hang it to air dry in
the sun.
--- Leave books, papers, and other items that cannot be cleaned with a liquid disinfectant or thrown away, outdoors in
the sunlight for several hours, or in an indoor area free of rodents for approximately 1 week before cleanup. After that
time, the virus should no longer be infectious. Wear rubber, latex, vinyl, or nitrile gloves and wipe the items with a
cloth moistened with disinfectant.
--- Disinfect gloves before removing them with disinfectant or soap and water. After removing the clean gloves,
thoroughly wash bare hands with soap and warm water.
Cleanup of Dead Rodents and Rodent Nests
Wear rubber, latex, vinyl, or nitrile gloves.
In the western United States, use insect repellent (containing DEET) on clothing, shoes, and hands to reduce the risk
of fleabites that might transmit plague.
Spray dead rodents and rodent nests with a disinfectant or a chlorine solution, soaking them thoroughly.
Place the dead rodent or nest in a plastic bag or remove the dead rodent from the trap and place it in a plastic bag
(See Precautions for Inside the Home.) When cleanup is complete (or when the bag is full), seal the bag, place it into a
second plastic bag, and seal the second bag. Dispose of the material in the double bag by 1) burying it in a 2- to 3-foot-deep
hole or 2) burning it or 3) discarding it in a covered trash can that is regularly emptied. Contact the local or state
health department concerning other appropriate disposal methods.
Clean up the surrounding area as described in Cleanup of Rodent Urine and Droppings and Contaminated Surfaces.
Disinfecting Solutions
Two types of disinfecting solutions are recommended to clean up rodent materials.
1. General-Purpose Household Disinfectant --- Prepare according to the label, if not prediluted. Almost any
agent commercially available in the United States is sufficient as long as the label states that it is a disinfectant. Effective
agents include those based on phenols, quaternary ammonium compounds, and hypochlorite.
2. Hypochlorite Solution --- A chlorine solution, freshly prepared by mixing 1½ cups of household bleach in 1 gallon
of water (or a 1:10 solution) can be used in place of a commercial disinfectant. When using chlorine solution, avoid
spilling the mixture on clothing or other items that might be damaged by bleach. Wear rubber, latex,
vinyl, or nitrile gloves when preparing and using chlorine solutions. Chlorine solutions should be prepared fresh daily.
Cleaning Sheds and Other Outbuildings
Before cleaning closed sheds and other outbuildings, ventilate the building by opening doors and windows for at least
30 minutes. Use cross ventilation if possible. Leave the area during the airing-out period. This airing helps to remove
infectious primary aerosols that might be created when hantavirus-infected rodents urinate. In substantially dirty or dusty
environments, additional protective clothing or equipment may be worn. Such equipment includes coveralls (disposable when possible)
and safety glasses or goggles, in addition to rubber, latex, vinyl, or nitrile gloves. For recommendations regarding precautions
for cleanup of outbuildings with heavy rodent infestations, see Special Precautions for Homes of Persons with
Confirmed Hantavirus Infection or Building with Heavy Rodent Infestations.
Special Precautions for Homes of Persons with Confirmed
Hantavirus Infection or Buildings with Heavy Rodent Infestations
Special precautions are indicated for cleaning homes or buildings with heavy rodent infestations. A rodent infestation
is considered heavy if piles of feces or numerous nests or dead rodents are observed. Persons cleaning these homes or
buildings
should contact the local or state public health agency or CDC for guidance. These precautions also can apply to
vacant dwellings that have attracted rodents while unoccupied and to dwellings and other structures that have been occupied
by persons with confirmed hantavirus infection. Workers who are either hired specifically to perform the cleanup or asked to
do so as part of their work activities should receive a thorough orientation from the responsible health agency or employer
about hantavirus transmission and disease symptoms and should be trained to perform the required activities safely.
Recommendations for Cleaning Homes or Buildings with Heavy
Rodent Infestations
If the building has been closed and unoccupied for a long period (weeks or months), ventilate the building by
opening doors and windows for at least 30 minutes before beginning any work. Use cross ventilation if possible.
Leave the area during the airing-out period. The ventilation helps to remove aerosolized virus inside the structure.
Persons involved in the cleanup should wear coveralls (disposable if possible); rubber boots or disposable shoe
covers; rubber, latex, vinyl, or nitrile gloves; protective goggles; and an appropriate respiratory protection device as detailed
in Precautions to Limit Occupational and Recreational Exposure to Rodents.
Personal protective gear should be decontaminated or safely disposed of upon removal at the end of the day. If the
coveralls are not disposable, they should be laundered on-site. If no laundry facilities are available, the coveralls should be
immersed in liquid disinfectant until they can be washed.
Unless burned on-site, all potentially infectious waste material from cleanup operations should be double-bagged
in appropriate plastic bags. The material in the bags should then be labeled as infectious and disposed of in accordance
with local regulations for infectious waste.
Persons involved in the cleanup who develop a febrile or respiratory illness within 45 days of the last potential
exposure should immediately seek medical attention and inform the attending physician of the potential occupational risk
of hantavirus infection. The physician should contact local health authorities promptly if hantavirus-associated illness
is suspected. A blood sample should be obtained and forwarded through the state health department for hantavirus
antibody testing.
Applicability and Updates
The control and prevention recommendations in this report represent general measures to minimize the likelihood of
human exposure to hantavirus-infected rodents in the Americas. Although different geographic areas might have varying housing
types and rodent populations, the precautions should be the same. The effect and utility of the recommendations will be
continually reviewed by CDC and the involved state and local health agencies as additional epidemiologic, field, and laboratory
data become available. These recommendations might be supplemented or modified in the future.
These recommendations and additional information concerning hantaviruses are periodically updated and made available
on CDC's website, All About Hantaviruses (http://www.cdc.gov/ncidod/disease/hanta/hps/index.htm). Additional
information can be obtained by contacting CDC, National Center for Infectious Diseases (NCID), Special Pathogens Branch, Mailstop
A-26, 1600 Clifton Road, N.E., Atlanta, GA 30333; e-mail dvd1spath@cdc.gov; fax
404-639-1509; or by telephone 404-639-1510.
Acknowledgments
This update is based on interim recommendations from James E. Childs, Sc.D.; Arnold F. Kaufmann, D.V.M.; and
Clarence J. Peters, M.D., NCID; and Richard L. Ehrenberg, M.D., National Institute for Occupational Safety and Health.
Graphics were produced by Amera R. Khan, M.P.H.; and Kent D. Wagoner, Ph.D., NCID. Jacob H. Creswell, M.P.H.; Kimberly
C. Dills, M.P.H.; and Emily S. Jentes, NCID, provided technical assistance and careful reviews of the manuscript. Kathleen
F. Cavallaro, M.S., NCID, helped coordinate numerous aspects of the manuscript preparation. The preparation of this
document was supported in part by an appointment to the Research Participation Program at CDC's NCID, Division of Viral
and Rickettsial Diseases, administered by the Oak Ridge Institute for Science and Education, Oak Ridge, TN, through
an interagency agreement between the U.S. Department of Energy and CDC.
References
Nichol ST, Spiropoulou CF, Morzunov S, et al. Genetic identification of a hantavirus associated with an outbreak of acute respiratory illness.
Science 1993;262:914--7.
Childs JE, Ksiazek TG, Spiropoulou CF, et al. Serologic and genetic identification of
Peromyscus maniculatus as the primary rodent reservoir for a
new hantavirus in the southwestern United States. J Infect Dis 1994;169:1271--80.
Duchin JS, Koster FT, Peters CJ, et al. Hantavirus pulmonary syndrome: a clinical description of 17 patients with a newly recognized disease. N Engl
J Med 1994;330:949--55.
Mills JN, Johnson JM, Ksiazek TG, et al. A survey of hantavirus antibody in small-mammal populations in selected United States national parks. Am
J Trop Med Hyg 1998;58:525--32.
Childs JE, Glass GE, Korch GW, LeDuc JW. The ecology and epizootiology of hantaviral infections in small mammal communities of Baltimore:
a review and synthesis. Bull Soc Vector Ecol 1988;13:113--22.
Mills JN, Ksiazek TG, Ellis BA, et al. Patterns of association with host and habitat: antibody reactive with Sin Nombre virus in small mammals in
the major biotic communities of the southwestern United States. Am J Trop Med Hyg 1997;56:273--84.
Song J-W, Baek L-J, Gajdusek DC, et al. Isolation of pathogenic hantavirus from white-footed mouse
(Peromyscus leucopus) [Letter]. Lancet 1994;344:1637.
Rollin PE, Ksiazek TG, Elliott LH, et al. Isolation of Black Creek Canal virus, a new hantavirus from
Sigmodon hispidus in Florida. J Med Virol 1995;46:35--9.
Ksiazek TG, Nichol ST, Mills JN, et al. Isolation, genetic diversity, and geographic distribution of Bayou virus (Bunyaviridae: Hantavirus). Am J
Trop Med Hyg 1997;57:445--8.
Sanchez AJ, Abbott KD, Nichol ST. Genetic identification and characterization of Limestone Canyon virus, a unique
Peromyscus-borne hantavirus. Virology 2001;286:345--53.
Hjelle B, Chavez-Giles F, Torrez-Martinez N, et al. Genetic identification of a novel hantavirus of the harvest mouse
Reithrodontomys megalotis.J Virol 1994;68:6751--4.
Wilson DE, Ruff S eds. The Smithsonian book of North American mammals. Washington, DC: Smithsonian Institution Press, 1999.
Burt WH, Grossenheider RP. A field guide to the mammals: North America north of Mexico. Peterson RT, ed. 3rd ed. Boston, MA:
Houghton Mifflin, 1976.
Lee HW, Calisher CH, Schmaljohn C. In: Lee HW, Calisher CH, Schmaljohn C, eds. Manual of hemorrhagic fever with renal syndrome
and hantavirus pulmonary syndrome. Seoul, Korea: WHO Collaborating Center for Virus Reference and Research (Hantaviruses), Asan Institute for
Life Sciences, 1999:250.
Glass GE, Watson AJ, LeDuc JW, Childs JE. Domestic cases of hemorrhagic fever with renal syndrome in the United States. Nephron 1994;68:48--51.
Hutchinson KL, Rollin PE , Peters CJ. Pathogenesis of a North American hantavirus, Black Creek Canal virus, in experimentally infected
Sigmodon hispidus. Am J Trop Med Hyg 1998;59:58--65.
Nuzum EO, Rossi CA, Stephenson EH, LeDuc JW. Aerosol transmission of Hantaan and related viruses to laboratory rats. Am J Trop Med
Hyg 1988;38:636--40.
Glass GE, Livingstone W, Mills JN, et al. Black Creek Canal virus infection in
Sigmodon hispidus in southern Florida. Am J Trop Med
Hyg 1998;59:699--703.
Mills JN, Childs JE. Rodent-borne hemorrhagic fever viruses. In: Williams ES, Barker IK, eds. Infectious diseases of wild mammals. 3rd ed. Ames,
IA: Iowa State University Press, 2001:254--70.
Tsai TF. Hemorrhagic fever with renal syndrome: mode of transmission to humans. Lab Anim Sci 1987;37:428--30.
Dournon E, Moriniere B, Matheron S, et al. HFRS after a wild rodent bite in Haute-Savoie---and risk of exposure to Hantaan-like virus in a
Paris laboratory. Lancet 1984;i:676--7.
Kawamata J, Yamanouchi T, Dohmae K, et al. Control of laboratory acquired hemorrhagic fever with renal syndrome (HFRS) in Japan. Lab Anim
Sci 1987;37:431--6.
Armstrong LR, Zaki SR, Goldoft MJ et al. Hantavirus pulmonary syndrome associated with entering or cleaning rarely used,
rodent-infested structures. J Infect Dis 1995;172:1166.
Peters CJ, Simpson GL, Levy H. Spectrum of hantavirus infection: hemorrhagic fever with renal syndrome and hantavirus pulmonary syndrome.
Annu Rev Med 1999;50:531--45.
Wells R, Young J, Williams R, et al. Hantavirus transmission in the United States. Emerg Infect Dis 1997;3:361--5.
Wells RM, Sosa Estani S, Yadon ZE, et al. An unusual hantavirus outbreak in southern Argentina: person-to-person transmission? Emerg Infect
Dis 1997;3:171--4.
Padula PJ, Edelstein A, Miguel SDL, López NM, Rossi CM, Rabinovich RD. Hantavirus pulmonary syndrome outbreak in Argentina:
molecular evidence for person-to-person transmission of Andes virus. Virology 1998;241:323--30.
Toro J, Vega JD, Khan AS, et al. An outbreak of hantavirus pulmonary syndrome, Chile, 1997. Emerg Infect Dis 1998;4:687--94.
Gligic A, Obradovic M, Stojanovic R, et al. Epidemic hemorrhagic fever with renal syndrome in Yugoslavia, 1986. Am J Trop Med Hyg
1989;41:102--8.
Niklasson B, LeDuc JW. Epidemiology of nephropathia epidemica in Sweden. J Infect Dis 1987;155:269--76.
Xu Z-Y, Guo CS, Wu Y-L, Zhang X-W, Liu K. Epidemiological studies of hemorrhagic fever with renal syndrome: analysis of risk factors and mode
of transmission. J Infect Dis 1985;152:137--44.
Zeitz PS, Butler JC, Cheek JE, et al. A case-control study of hantavirus pulmonary syndrome during an outbreak in the southwestern United States.
J Infect Dis 1995;171:864--70.
Prince HN, Prince DL, Prince RN. Principles of viral control and transmission. In: Block SS, ed. Disinfection, sterilization, and preservation. 4th
ed. Philadelphia, PA: Lea & Febiger, 1991:411--44.
Schmaljohn C, Huggins J, Calisher CH. Laboratory and field safety. In: Lee HW, Calisher CH, Schmaljohn C, eds. Manual of hemorrhagic fever
with renal syndrome and hantavirus pulmonary syndrome. Seoul, Korea: WHO Collaborating Center for Virus Reference and Research
(Hantaviruses), Asan Institute for Life Sciences, 1999:192--8.
Glass GE, Johnson JS, Hodenbach GA, et al. Experimental evaluation of rodent exclusion methods to reduce hantavirus transmission to humans
in rural housing. Am J Trop Med Hyg 1997;56:359--64.
Scott HG, Borom MR. Rodent-borne disease control through rodent stoppage. Washington, DC: US Department of Health, Education, and
Welfare, Public Health Service, CDC, 1977; DHEW(CDC) publication no. 77-8343.
Pratt HD, Brown RZ. Biological factors in domestic rodent control. Atlanta, GA: US Department of Health, Education, and Welfare,
1979; DHEW(CDC) publication no. 79-8144.
Hoddenbach G, Johnson J, Disalvo C. Mechanical rodent proofing techniques. Washington, DC: US Department of the Interior, National
Park Service, Public Health Program, 1997.
US Department of Labor. Occupational Safety and Health Administration. Respiratory Protection (includes appendices A--D, revised July 1,
1999). Federal Register 1999;5:402--27 (29 CFR 1910.134).
National Institute for Occupational Safety and Health. NIOSH guide to industrial respiratory protection. Cincinnati, OH: US Department of
Health and Human Services, Public Health Service, CDC, National Institute for Occupational Safety and Health, 1987; NIOSH technical
guide; DHHS(NIOSH) publication no. 87-116.
Mills JN, Yates TL, Childs JE, et al. Guidelines for working with rodents potentially infected with hantavirus. J Mammology 1995;76:716--22.
Mills JN, Childs JE, Ksiazek TG, Peters CJ, Velleca WM. Methods for trapping and sampling small mammals for virologic testing. Atlanta GA:
US Department of Health and Human Services, Public Health Service, CDC, 1995.
† A rodent-proof container is made of thick plastic, glass, or metal and has a tight-fitting lid.
§ Only spring-loaded traps that kill rodents should be used. Live and sticky traps that do not kill rodents are not recommended. Infectious aerosols might
be produced when live rodents urinate or struggle to free themselves. Disposal of live rodents also introduces the risk of rodent bite, which also can result in infection.
¶ See Precautions for Cleanup of Rodent-Contaminated Areas and Dead Rodents for detailed information regarding making a chlorine solution.
** Follow the recommendations specified in the section Precautions for Cleanup of Rodent-Contaminated Areas and Dead Rodents, if rodent urine,
droppings, nests, or dead rodents are encountered while these measures are being carried out.
†† Lath screen or metal is a light-gauge metal mesh and is commonly installed over wooden walls before plaster is applied. A galvanized product
is preferable. Lath screen is malleable and can be folded and pushed into larger holes. These materials can be found in the masonry or building materials section
at hardware or building supply stores.
§§ STUF-FIT is a soft copper-mesh material that might be preferable to steel wool because it does not rust and is not easily pulled apart by rodents. It
can be obtained from pest control retail stores or from Allen Special Products (telephone 800-848-6805).
¶¶ Illustrated, complete instructions for rodent-proofing are available 1) in the National Park Service's manual, Mechanical Rodent Proofing Techniques;
2) on CDC's website, All About Hantaviruses (http://www.cdc.gov/ncidod/diseases/hanta/hps/index.htm); and 3) from CDC's Ramah Home Seal-up
protocol, Special Pathogens Branch (e-mail dvd1spath@cdc.gov).
The following persons provided consultation in the development of the previous or current versions of these recommendations:
Michael A. Bogan, Ph.D., U.S. Fish and Wildlife Service, Fort Collins, CO; Patrick O. Bohan, M.S., Indian Health Service, Navajo Regional Office, Window Rock, AZ;
Ted L. Brown, M.S., New Mexico Department of the Environment, Sante Fe, NM; James E. Cheek, M.D., Indian Health Service, Albuquerque, NM;
Richard M. Davis, D.Sc., California Department of Health Services, Ventura, CA; John Doll, Ph.D., Arizona Department of Health Services, Phoenix,
AZ; Richard L. Ehrenberg, M.D., National Institute for Occupational Safety and Health, Atlanta, GA; Eric Esswein, M.S.P.H., National Institute
for Occupational Safety and Health, Denver, CO; Kathleen A. Fagerstone, Ph.D., U.S. Department of Agriculture, Denver, CO; William
Ferraro, Philadelphia Department of Public Health, Philadelphia, PA; Curtis L. Fritz, D.V.M., Ph.D., California Department of Health Services, Sacramento,
CA; Gregory Glass, Ph.D., Department of Molecular Microbiology and Immunology, Johns Hopkins School of Hygiene and Public Health, Baltimore, MD;
Marcia Goldoft, M.D., Washington State Department of Health, Seattle, WA; Jerry M. Hershovitz, Division of Emergency and Environmental
Health Services, National Center for Environmental Health, Atlanta, GA; Randall B. Hirschhorn, M.S., Philadelphia Department of Public Health,
Philadelphia, PA; Gerry Hoddenbach, M.S., Hoddenbach Consulting, Torrey, UT; William Jackson, Ph.D., Bowling Green State University, Bowling Green, OH;
Karl Johnson, M.D., University of New Mexico, Albuquerque, NM; James W. LeDuc, Ph.D., Division of Viral and Rickettsial Diseases, National Center
for Infectious Diseases, Atlanta, GA; Craig R. Nichols, M.P.H., Utah Department of Health, Salt Lake City, UT; Mark G. Novak, Ph.D.,
California Department of Health Services, Sacramento, CA; Robert Parmenter, Ph.D., University of New Mexico, Albuquerque, NM; Timothy M. Radtke,
M.S., Office of Occupational Safety and Health, U.S. Department of the Interior, Denver, CO; Robert N. Reynolds, M.S., U.S. Department of
Agriculture,
Lakewood, CO; Luis Ruedas, Ph.D., Division of Viral and Rickettsial Diseases, National Center for Infectious Diseases, Atlanta, GA; Connie
S. Schmaljohn, Ph.D., U.S. Army Medical Research Institute for Infectious Diseases, Fort Detrick, MD; Herman F. Shorty, Navajo Nation Office
of Environmental Health, Window Rock, AZ; Thomas M. Smylie, U.S. Department of Agriculture, Albuquerque, NM; Rosemary Sokas, M.D.,
National Institute for Occupational Safety and Health, Washington, D.C.; Dale T. Tanda, Colorado Department of Health, Denver, CO; Ronald E. Vorhees,
M.D., New Mexico Department of Health, Sante Fe, NM; Richard Yanagihara, M.D., National Institutes of Health, Bethesda, MD.
Use of trade names and commercial sources is for identification only and does not imply endorsement by the U.S. Department of
Health and Human Services.References to non-CDC sites on the Internet are
provided as a service to MMWR readers and do not constitute or imply
endorsement of these organizations or their programs by CDC or the U.S.
Department of Health and Human Services. CDC is not responsible for the content
of pages found at these sites. URL addresses listed in MMWR were current as of
the date of publication.
Disclaimer
All MMWR HTML versions of articles are electronic conversions from ASCII text
into HTML. This conversion may have resulted in character translation or format errors in the HTML version.
Users should not rely on this HTML document, but are referred to the electronic PDF version and/or
the original MMWR paper copy for the official text, figures, and tables.
An original paper copy of this issue can be obtained from the Superintendent of Documents,
U.S. Government Printing Office (GPO), Washington, DC 20402-9371; telephone: (202) 512-1800.
Contact GPO for current prices.
**Questions or messages regarding errors in formatting should be addressed to
mmwrq@cdc.gov.
