San Joaquin County Health Officer Karen Furs on Friday confirmed that a 48-year-old man living in Stockton is the first human with West Nile virus infection in San Joaquin County this year.
The man reported having no symptoms, but tested positive for the virus when donating blood. Although for reporting purposed this does not meet the definition for the California Department of Public Health to count it as a case, it does indicate that there is currently active transmission of West Nile virus to people in San Joaquin County.
West Nile virus is most commonly transmitted to humans and animals through the bite of a mosquito infected with the virus. Hot weather, abandoned swimming pools and standing water create ideal conditions for the development of mosquitoes and the subsequent spread of the virus.
Most individuals who are infected with West Nile virus will not experience any illness. About one in five people infected with the virus will develop West Nile fever with symptoms of headache, fever and fatigue. However, some individuals — less than 1 percent — will develop serious neurologic illness such as encephalitis or meningitis.
Individuals 50 years of age and older have a higher chance of getting sick and are more likely to develop serious symptoms when infected with West Nile virus. Recent data also indicate that those with diabetes and/or hypertension are at greatest risk for serious illness.