State health officials say the mosquito-borne West Nile virus has officially returned to Massachusetts.
The Department of Public Health announced Thursday that West Nile was detected in mosquitoes collected in Boston last week, the first positive sample of the year in the state.
No human cases have been reported so far.
A year ago there were 49 confirmed human cases of West Nile, the most ever reported in a single year in Massachusetts.
State epidemiologist Catherine Brown says the risk for human infection generally peaks in August.
As always, health officials are advising people to protect themselves from mosquito-borne illnesses such as West Nile and Eastern Equine Encephalitis by using mosquito repellent, draining standing water near their homes and repairing any tears in window screens.