BOSTON – For the first time since testing began, mosquitoes carrying the eastern equine encephalitis virus have been found on Cape Cod. The news comes shortly after the state health department confirmed a second human case of EEE in as many days.

Derek Ashworth, 23, of Acushnet, was hospitalized and remained in serious condition Thursday, according to his father, Rochester Fire Chief Scott Ashworth. His symptoms began on Aug. 11 and he was admitted to the hospital on Aug. 12, officials said.

On Wednesday, officials confirmed a 53-year-old Lakeville woman has been diagnosed as the first human case of the mosquito-borne virus.

The woman, whose name was not released, also was in serious condition at an undisclosed Boston hospital, according to state health officials. Ashworth said his son is at Boston Medical Center.

To combat mosquito-borne viruses, almost 160,000 acres in Plymouth and Bristol counties were sprayed with insecticide for the first time in 16 years. The woman was likely infected before the spraying began, according to health officials, and Ashworth lived outside of the spray area.

Officials said they reinstated the spraying program because they expected a larger-than-usual population of mosquitoes after this year’s record rainfall. So far this year, more than 50 mosquitoes have tested positive for the virus, including a sample collected in Dennis, Mass., on Monday.

Although the spraying reduced mosquito populations by at least 60 percent, Dr. Alfred DeMaria, chief medical officer at the state Department of Public Health said Wednesday, “It’s a misapprehension to think that spraying eliminated the risk. It only reduced the risk from ‘really bad’ to ‘bad.”‘

The EEE virus, like West Nile, is transmitted to humans through mosquito bites. Symptoms range from mild flulike illness to encephalitis – inflammation of the brain – coma and death. There is no cure for EEE. According to state health officials, about three of every 10 people who get the virus could be expected to die from it.

Mosquitoes and birds in the state also have tested positive for West Nile virus this year, state officials said.

In order to reduce the possibility of exposure to both viruses, health officials said people should reduce mosquito populations near their homes by eliminating any standing water and removing garbage – conditions that mosquitoes favor.

DeMaria also recommended wearing long sleeved clothing at dawn and dusk, when mosquitoes are most active, and using an insect repellent containing DEET.