Statistics & Maps
LAC virus disease is a nationally notifiable condition. Cases are reported to CDC by state and local health departments using the national surveillance case definition. To ensure standardization of reporting across the country, CDC recommends that the national surveillance case definition (standardized reporting criteria) be consistently applied by all state health departments.
In the United States, 30-90 La Crosse encephalitis (LAC) virus neuroinvasive disease cases are reported each year. There is substantial under-diagnosis and under-reporting of less severe cases of LAC disease; therefore, reported LAC neuroinvasive disease cases are used to compare trends over time and place.
LAC virus disease cases occur primarily from late spring through early fall, but in subtropical endemic areas (e.g., the Gulf states), cases can occur in winter as long as mosquitoes are active. Historically, most cases of LAC virus neuroinvasive disease were reported from the upper Midwestern states (Ohio, Wisconsin, Minnesota, Indiana, Illinois, and Iowa). Recently, more cases have been reported from northeastern, mid-Atlantic and southeastern states (North Carolina, Tennessee, West Virginia, Georgia, Virginia, Kentucky, and Rhode Island).
Anyone in an area where LAC virus is circulating can get infected with the virus. The risk is highest for people who live, work, or recreate in woodland habitats, because of greater exposure to potentially infected mosquitoes.
Source: ArboNET, Arboviral Diseases Branch, Centers for Disease Control and Prevention
Source: ArboNET, Arboviral Diseases Branch, Centers for Disease Control and Prevention
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State | Number of Reported Cases |
---|---|
Alabama | 1 |
Florida | 1 |
Georgia | 8 |
Illinois | 3 |
Indiana | 5 |
Iowa | 1 |
Kansas | 1 |
Kentucky | 6 |
Louisiana | 1 |
Maryland | 1 |
Michigan | 2 |
Minnesota | 17 |
Mississippi | 3 |
North Carolina | 162 |
Ohio | 205 |
Rhode Island | 2 |
South Carolina | 4 |
Tennessee | 112 |
Texas | 4 |
Virginia | 9 |
West Virginia | 47 |
Wisconsin | 28 |
Source: ArboNET, Arboviral Diseases Branch, Centers for Disease Control and Prevention
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Data table: This map shows the distribution of La Crosse virus neuroinvasive disease average annual incidence by county of residence from 2012 through 2021. Counties are shaded according to incidences ranging from less than 1.00, 1.00 to 2.49, and greater than 2.50 per 100,000 population. Shaded counties are primarily distributed in eastern half of the country. Most of the highest incidence counties are along the Appalachian range and central Ohio.
Additional Maps, Charts, and Tables
La Crosse virus disease cases and deaths reported to CDC by year and clinical presentation, 2012-2021
Neuroinvasive disease | Non-neuroinvasive disease | Total | ||||
---|---|---|---|---|---|---|
Year | Cases No. |
Deaths No. (%) |
Cases No. |
Deaths No. (%) |
Cases No. |
Deaths No. (%) |
2012 | 71 | 1 (1) | 7 | 0 (0) | 78 | 1 (1) |
2013 | 77 | 2 (3) | 8 | 0 (0) | 85 | 2 (2) |
2014 | 76 | 3 (4) | 4 | 0 (0) | 80 | 3 (4) |
2015 | 51 | 0 (0) | 4 | 0 (0) | 55 | 0 (0) |
2016 | 31 | 0 (0) | 4 | 0 (0) | 35 | 0 (0) |
2017 | 63 | 0 (0) | 0 | 0 (0) | 63 | 0 (0) |
2018 | 83 | 0 (0) | 3 | 0 (0) | 86 | 0 (0) |
2019 | 48 | 0 (0) | 7 | 0 (0) | 55 | 0 (0) |
2020 | 84 | 0 (0) | 4 | 0 (0) | 88 | 0 (0) |
2021 | 39 | 0 (0) | 1 | 0 (0) | 40 | 0 (0) |
Total | 623 | 6 (1) | 42 | 0 (0) | 665 | 6 (1) |
Source: ArboNET, Arboviral Diseases Branch, Centers for Disease Control and Prevention
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La Crosse virus disease cases reported to CDC by state of residence, 2012–2021
State | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 | 2019 | 2020 | 2021 | Total |
---|---|---|---|---|---|---|---|---|---|---|---|
Alabama | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
Alaska | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Arizona | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Arkansas | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
California | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Colorado | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Connecticut | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Delaware | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Dist. of Columbia | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Florida | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
Georgia | 0 | 1 | 2 | 2 | 0 | 2 | 0 | 1 | 1 | 0 | 9 |
Hawaii | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Idaho | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Illinois | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 3 |
Indiana | 3 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 6 |
Iowa | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 1 |
Kansas | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
Kentucky | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 5 | 0 | 6 |
Louisiana | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
Maine | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Maryland | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 1 |
Massachusetts | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Michigan | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 | 2 |
Minnesota | 4 | 5 | 4 | 1 | 3 | 1 | 0 | 1 | 0 | 0 | 19 |
Mississippi | 1 | 3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 4 |
Missouri | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Montana | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Nebraska | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Nevada | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
New Hampshire | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
New Jersey | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
New Mexico | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
New York | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
North Carolina | 26 | 13 | 23 | 11 | 8 | 21 | 24 | 6 | 21 | 9 | 162 |
North Dakota | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Ohio | 13 | 16 | 31 | 24 | 9 | 13 | 39 | 26 | 33 | 18 | 222 |
Oklahoma | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Oregon | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Pennsylvania | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Puerto Rico | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Rhode Island | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 2 |
South Carolina | 1 | 1 | 0 | 1 | 0 | 0 | 0 | 0 | 1 | 0 | 4 |
South Dakota | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Tennessee | 9 | 23 | 11 | 4 | 3 | 17 | 13 | 12 | 15 | 7 | 114 |
Texas | 3 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 4 |
Utah | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Vermont | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Virginia | 2 | 2 | 2 | 0 | 0 | 0 | 2 | 0 | 1 | 0 | 9 |
Washington | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
West Virginia | 14 | 11 | 2 | 4 | 8 | 4 | 6 | 3 | 7 | 1 | 60 |
Wisconsin | 2 | 8 | 4 | 6 | 4 | 2 | 0 | 3 | 2 | 2 | 33 |
Wyoming | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Total | 78 | 85 | 80 | 55 | 35 | 63 | 86 | 55 | 88 | 40 | 665 |
Source: ArboNET, Arboviral Diseases Branch, Centers for Disease Control and Prevention
To request data for previous years, please email dvbid2@cdc.gov.