Maryland's health department has confirmed three cases of West Nile virus in the Baltimore area.
The department announced this year's first confirmed cases in the state on Friday. All three people are adults.
Health officials say West Nile virus has been detected in mosquito pools collected in Montgomery and Worcester counties. A mosquito pool is a group of mosquitoes collected at one of several trap sites across the state.
Dr. Joshua Sharfstein, the state's health secretary, says this is the time of year when West Nile virus cases occur in Maryland.
He is advising residents to avoid areas of high mosquito activity and unnecessary outdoor activities at dawn and dusk when mosquitoes are most active. He also advises wearing long pants, long-sleeved shirts and hats when concerned about mosquito exposure.