Second human case of West Nile virus confirmed in Jefferson County as Louisville-area mosquitoes test positive in new neighborhoods

Louisville Metro Public Health and Wellness confirmed a second human case of West Nile virus in Jefferson County on Friday, as mosquito testing showed West Nile-infected mosquitoes spreading into more parts of the metro area, according to the department’s latest update.

The health department said it has identified infected mosquitoes in nine additional neighborhoods this month. The findings indicate the virus is present in the local mosquito population beyond earlier detection areas, raising the risk that additional residents could be exposed during peak mosquito season.

Officials did not describe the patient’s age or condition in the report, but they said the new confirmation brings the county’s total to two human cases for the current outbreak period. The agency framed the mosquito results as an early indicator of neighborhood-level risk rather than a direct measure of how many people will become ill.

In its update, the department emphasized that West Nile virus is transmitted through mosquito bites and that infected mosquitoes can be detected in multiple neighborhoods during the same season. The department’s announcement points residents toward heightened awareness as more areas are flagged by routine surveillance.

West Nile virus surveillance in Louisville relies on ongoing mosquito testing, which helps public health officials target community messaging and mosquito-control priorities. As additional neighborhoods are added, officials said the pattern reflects the expansion of where mosquitoes carrying the virus have been found.

Public health officials urged continued vigilance from residents, including taking steps to reduce mosquito exposure consistent with local prevention guidance. With more infected areas identified, the department said the next days and weeks will be important for monitoring new mosquito findings and any additional human symptoms that may emerge after exposure.

The department’s confirmation of a second human case underscores the continued presence of the virus in the Jefferson County area this year. Residents are expected to watch for public health updates as mosquito testing results are posted and as the department assesses whether more neighborhoods are added to the current map of detections.