A Salt Lake County resident died from West Nile virus last week, health officials reported Wednesday. It is Utah’s first known fatality this year connected to the mosquito-borne illness.

The person was older than 65 and already suffered from other health problems when diagnosed with neuroinvasive West Nile virus, a relatively severe form of the disease, according to a news release from the Salt Lake County Health Department.

Six people died from West Nile last year in Utah. So far this summer, the virus has been detected in 30 different mosquito groups in Salt Lake County alone, health officials said.

“There are a growing number of mosquitoes in the county carrying the disease, so it is now especially important that residents be vigilant in protecting themselves from mosquito bites, particularly in the hours from dusk to dawn,” said Ilene Risk, the department’s epidemiology director.

Although mosquitoes are active throughout the summer, West Nile virus typically doesn’t begin to appear until late summer, said Nicholas Rupp, department spokesman.

“Around Memorial Day, people should just start getting in the habit of putting mosquito repellent on — but now is the time when it becomes really important,” he said.

To reduce risk of exposure to the virus, Utahns should use repellent, wear long sleeves and pants after dusk, remove standing water outside their homes, clean their gutters and keep grass and weeds trimmed short, health officials advised.

Most people with West Nile virus won’t ever know they are infected, Rupp said. Only 20 percent show symptoms — typically a mild fever — and less than 1 percent will develop the severe symptoms associated with infection of the nervous system. Symptoms usually begin three to 14 days after infection.