Historic Data (2004-2024)

Key points

  • ArboNET is a national arboviral surveillance system managed by CDC and state health departments.
  • The visuals on this dashboard display Powassan virus data from 2004 – 2024.

View the historic data

Notice

We are in the process of updating our historic data webpage. During this transition, finalized 2023 and preliminary 2024 data will be temporarily unavailable.

The 2024 data are preliminary and subject to change. Data are current as of June 4, 2025.

Cumulative data for 2004-2024

*Average annual incidence data is unavailable for Connecticut at the county level. Connecticut changed from counties to planning regions in 2022. Annual county or planning region level case counts can be found below.

Explore human data for 2004-2024

Please note – users may experience slow load times after selecting filters. Please allow the visualizations to fully load after selecting filters, which will be indicated by an updated visual title. The 'Type of case' selection option 'All disease cases' includes all reported neuroinvasive and non-neuroinvasive disease cases.

Explore county data for 2004-2024

Please note – users may experience slow load times after selecting filters. Please allow the visualizations to fully load after selecting filters.

View 2022 Connecticut data

Limitations of ArboNET data

Surveillance data have several limitations that should be considered when using and interpreting the data.

  1. Under-reporting is a limitation common to all surveillance systems that rely on healthcare providers to consider the disease as a possible diagnosis in a patient, obtain the appropriate laboratory test, and report confirmed cases to public health authorities.
  2. Cases of mild illness (non-neuroinvasive disease) are more likely to be underreported compared to more severe disease (neuroinvasive) cases. The degree of underreporting varies by disease awareness and healthcare-seeking behavior in any area. Surveillance data for non-neuroinvasive disease should not be used to make comparisons of disease activity between different locations or over time.
  3. Surveillance data are reported by county of residence, not the location (county or state) of exposure.
  4. Non-human surveillance is conducted variably across the country. Absence of non-human activity reported to CDC should not be interpreted as no risk.
  5. There is a lag in case reporting to CDC and states and territories may publish surveillance data on different schedules than CDC.
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