Health authorities have warned residents to protect themselves against bites from mosquitoes that can transmit a rare virus that has killed at least six people in three states this year.

An increase in cases of the disease, called Eastern equine encephalitis, has prompted authorities in Michigan, Massachusetts, Connecticut, Rhode Island, North Carolina and New Jersey to issue the warnings: Remove standing water. Use repellent. Seal windows and doors.

The six deaths were in Michigan, Massachusetts and Rhode Island, according to state officials.

In Michigan, three peopl e have died from the disease, for which there is no known vaccine, in a total of seven confirmed cases this year, state officials said this week. The deaths occurred between mid-August and early September, according to the Michigan Department of Health and Human Services.

The state is experiencing its worst outbreak of the disease in more than a decade, Joneigh Khaldun, the state’s chief medical executive, said in a statement on Tuesday. The state reported six cases in 2002, the last time it recorded a large number of people with the virus.