A man in his 70s from Norfolk County has been hospitalized with West Nile virus, the second case of the mosquito-borne illness detected in Massachusetts this year.

The state Department of Public Health reported the case Tuesday, after testing was completed by the Public Health Laboratory. The man is improving, the department said.

The health department is investigating where the man most likely was bitten by an infected mosquito.

“Massachusetts is still in the peak season for possible West Nile virus infection in people,’’ Dr. Catherine Brown, state public health veterinarian, said in a statement. “Although Labor Day is the unofficial end of summer, it is not the end of mosquito season.’’

She urged people to use insect repellent; wear long sleeves, long pants, and socks; and stay inside as much as possible between dusk and dawn, when mosquitoes are most active.

The virus can infect people of all ages, and most will have no symptoms. When symptoms occur, they tend to include fever and flu-like illness. In rare cases, the virus causes serious neurologic illness.

More information can be found on the Arbovirus Surveillance Information web page at www.mass.gov/dph/mosquito or by calling the Department of Public Health Epidemiology Program at 617-983-6800.

Felice J. Freyer can be reached at felice.freyer@globe.com.