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About Jamestown Canyon

In the United States, an average of 23 Jamestown Canyon virus neuroinvasive disease cases are reported each year (2011-2022). There is significant under-diagnosis and under-reporting of less severe cases of Jamestown Canyon virus disease, therefore reported neuroinvasive disease cases are used to compare trends over time and place. Jamestown Canyon virus disease is a nationally notifiable condition. 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.

Most Jamestown Canyon virus infections occur from April through September. The virus is found throughout much of the United States, but Minnesota and Wisconsin have reported more than half of all cases. The recent increase in reported cases likely reflects increased awareness and testing, but also could be due to an increase in disease incidence.