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Volume 31, Number 5—May 2025
Research

Powassan and Eastern Equine Encephalitis Virus Seroprevalence in Endemic Areas, United States, 2019–2020

Hannah Padda, Claire Y.-H. Huang, Kacie Grimm, Brad J. Biggerstaff, Jeremy P. Ledermann, Janae Raetz, Karen Boroughs, Eric C. Mossel, Stacey W. Martin, Jennifer A. Lehman, Rebecca L. Townsend, David Krysztof, Paula Saá, Emily T.N. Dinh, Mary Grace Stobierski, Brenda Esponda-Morrison, Karen Ann A. Wolujewicz, Matthew Osborne, Catherine M. Brown, Brandi Hopkins, Elizabeth K. Schiffman, Alex Garvin, Xia Lee, Rebecca A. Osborn, Ryan J. Wozniak, Aaron C. Brault, Sridhar V. Basavaraju, Susan L. Stramer, J. Erin Staples, and Carolyn V. GouldComments to Author 
Author affiliation: Author affiliations: Centers for Disease Control and Prevention, Fort Collins, Colorado, USA (H. Padda, C.Y.-H. Huang, B.J. Biggerstaff, J.P. Ledermann, J. Raetz, K. Boroughs, E.C. Mossel, S.W. Martin, J.A. Lehman, A.C. Brault, J.E. Staples, C.V. Gould); American Red Cross, Rockville, Maryland, USA (K. Grimm, R.L. Townsend, D. Krysztof, P. Saá); Michigan Department of Health and Human Services, Lansing, Michigan, USA (E.T.N. Dinh, M.G. Stobierski); Connecticut Department of Public Health, Hartford, Connecticut, USA (B. Esponda-Morrison, K.A.A. Wolujewicz); Massachusetts Department of Public Health, Boston, Massachusetts, USA (M. Osborne, C.M. Brown, B. Hopkins); Minnesota Department of Health, Saint Paul, Minnesota, USA (E.K. Schiffman, A. Garvin); Wisconsin Department of Health Services, Madison, Wisconsin, USA (X. Lee, R.A. Osborn, R.J. Wozniak); Centers for Disease Control and Prevention, Atlanta, Georgia, USA (S.V. Basavaraju); Infectious Disease Consultant, North Potomac, Maryland, USA (S.L. Stramer)

Main Article

Table 2

Blood donor and estimated population seroprevalence for Powassan virus in selected endemic counties in study of Powassan virus and Eastern equine encephalitis virus seroprevalence in endemic areas, United States, 2019–2020

Calculated sample size No. samples
tested		 No. (%) donors
 % Seroprevalence (95% CI)
Neutralizing antibody positive Neutralizing antibody and IgM positive
Estimated* Estimated recent†
Connecticut
Fairfield 422 420 2 (0.48) 1 (0.24) 0.29 (0.04–1.04) 0.15 (0.00–0.81)
Litchfield
 164
 164
 2 (1.2)
 2 (1.2)
 1.68 (0.14–6.70)
 1.68 (0.14–6.63)
Massachusetts
Barnstable 21 21 0 0 0 (0–16.1) 0 (0–16.1)
Essex 184 184 3 (1.6) 2 (1.1) 1.12 (0.22–3.32) 0.81 (0.09–2.96)
Middlesex 339 337 2 (0.59) 0 0.98 (0.10–3.67) 0 (0–1.09)
Norfolk 206 206 1 (0.49) 0 0.70 (0.02–3.81) 0 (0–1.77)
Worcester
 160
 160
 0
 0
 0 (0–2.28)
 0 (0–2.28)
Minnesota
Anoka‡ 141 141 2 (1.4) 1 (0.71) 1.42 (0.39–5.02) 0.71 (0.04–3.91)
Cass§ 3 3 0 0 – –
Itasca 8 8 0 0 0 (0–36.9) 0 (0–36.9)
Morrison
 8
 8
 0
 0
 0 (0–36.9)
 0 (0–36.9)
Wisconsin
Jackson 16 16 1 (6.3) 0 11.48 (0.82–40.92) 0 (0–20.59)
Shawano§ 3 3 0 0 – –
Trempealeau 19 19 1 (5.3) 0 11.47 (0.87–40.3) 0 (0–17.65)
Wood 78 80 2 (2.5) 0 2.12 (0.27–7.37) 0 (0–4.51)

*Neutralizing antibodies present. †Neutralizing antibodies and IgM present. ‡County where cases were suspected to be travel-associated rather than locally acquired. §Counties with <5 samples were excluded from seroprevalence calculations.

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Page created: March 18, 2025
Page updated: April 25, 2025
Page reviewed: April 25, 2025
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