BATTLE CREEK, Mich. — Tests confirm two Mexican gray wolf pups at southern Michigan zoo have died of a rare mosquito-borne virus as health officials work to curb the spread of the virus in people and animals.

Binder Park Zoo in Battle Creek says results received this week confirm the pups that died in early September were killed by Eastern equine encephalitis.

The state Department of Health and Human Services reports the virus has been confirmed in humans or animals in at least 12 Michigan counties. Three people in southwestern Michigan have died.

People are urged to guard against mosquito bites. The department is encouraging officials in affected counties to consider postponing, rescheduling or canceling outdoor activities including sports occurring at or after dusk until there’s a hard frost. Aerial spraying is being considered.