The United States is experiencing a significant increase in West Nile virus cases, prompting urgent warnings from health officials. According to the Centers for Disease Control and Prevention (CDC), as of September 9th, 2025, at least 771 human cases have been reported across 39 states. A concerning 490 of these cases are classified as neuroinvasive, indicating severe infections impacting the brain and central nervous system.
West Nile virus, the leading mosquito-borne illness in the continental US, typically peaks during the summer and fall mosquito season. However, experts attribute the lengthening mosquito season to a warming climate, increasing the risk of transmission and the potential for widespread outbreaks. This upward trend highlights the need for increased public awareness and preventative measures.
Massachusetts, following the announcement of two additional cases, has urged its residents to remain vigilant. State Public Health Commissioner Dr. Robbie Goldstein emphasized that the risk of infection persists until the first hard frost, likely weeks away. He strongly advised the public to utilize mosquito repellent, wear protective clothing, and eliminate standing water around their homes to minimize mosquito breeding grounds.
The CBS News data team, utilizing data from ArboNET, a national arboviral surveillance system, continues to track confirmed West Nile virus cases nationwide. This data is updated bi-weekly on Tuesdays. The virus often presents flu-like symptoms; however, less than 1 in 150 infected individuals experience severe neurological complications, resulting in brain and spinal cord inflammation, as explained by CBS News chief medical correspondent Dr. Jon LaPook.
While most individuals infected with West Nile virus remain asymptomatic, those who develop symptoms typically experience them 2 to 6 days after a mosquito bite, although this can vary up to 14 days, or even longer for individuals with compromised immune systems. Importantly, there is no specific treatment for West Nile virus. The focus remains on preventative measures, such as those outlined by Dr. Goldstein, to reduce the risk of mosquito bites. Individuals at increased risk, including the elderly and those with weakened immune systems, are urged to take extra precautions.
This ongoing situation underscores the importance of community-wide efforts in mosquito control and personal protective measures to mitigate the spread of this serious illness.
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Originally published at: https://www.cbsnews.com/news/west-nile-virus-cases-map-2025/
