The New York City Health Department has detected West Nile virus in some Staten Island mosquitoes.
The virus turned up for the first time in the borough this season.
The health department says it has increased surveillance activity in response.
The infected mosquitoes were collected from the neighborhoods of New Dorp Beach and Bull's Head.
The department is setting up additional traps and treating catch basins in the affected areas. No human cases have been detected this season.