A mosquito has tested positive for West Nile virus in Massachusetts for the first time this year, the Department of Public Health said Thursday.
The infected mosquito was caught in Medford on Tuesday -- no person or animal has yet been diagnosed with the virus, which can cause severe illness.
Acting Public Health Commissioner Margret Cooke said in a statement that the first West Nile-"infected mosquito of the season is always a signal that it is time to start taking steps to avoid mosquito bites."
Eight people were diagnosed with West Nile last year, according to the department. The most cases reported in one year was 49 in 2018.
It's one of two mosquito-borne diseases that's a threat to people in Massachusetts each year. The other is eastern equine encephalitis, or EEE, which has not yet been detected in people or animals this year.
But Cooke said the West Nile finding is a reminder that people can protect themselves from mosquitoes, and the viruses they transmit, like wearing insect repellent when outside and avoiding dusk and dawn, when the insects are most active.