New York State Health Department officials said 20 human cases...

New York State Health Department officials said 20 human cases of West Nile virus have been reported this year. Credit: AP/USDA Agricultural Research Service via AP

Two additional cases of West Nile virus were reported by Suffolk County Health officials on Friday, bringing the total number of county residents infected this year to seven.

Both of the individuals, one over 50 and one under 50, are from the Town of Islip and started experiencing symptoms in early August. They did not need to be hospitalized and have since recovered, officials said.

A state Department of Health report released Thursday reported two Nassau cases of West Nile virus last week.

West Nile virus is transmitted to people when they are bitten by infected mosquitoes. Experts believe only about 20% of people who are infected develop noticeable symptoms.

Some people may experience a mild illness with fever, headache and body aches. But the virus can cause more serious disease with high fever, neck stiffness, muscle weakness and paralysis. It can be fatal.

People over the age of 50 and those with medical conditions are at a higher risk, and Suffolk County Health Commissioner Dr. Gregson Pigott advised them to be "extra vigilant in avoiding mosquito bites" and to get medical treatment if they're feeling ill.

"We suspect that many more Suffolk County residents may have been infected with West Nile virus but are not counted because they experienced mild symptoms, like headache or swollen glands, and didn’t seek medical attention," Pigott said in a statement.

West Nile virus is the leading cause of mosquito-borne disease in the United States, according to the Centers for Disease Control and Prevention. So far, the agency has reported 289 cases nationally across 33 states.

New York State Health Department officials said 20 human cases of West Nile virus have been reported so far this year, 10 in New York City and 10 outside New York City.

Last year, there were five confirmed human cases in Suffolk County and 18 in Nassau County.

People can avoid mosquito bites by using repellent, avoid going outside after dusk when mosquitoes are active and remove standing water from their property.

Suffolk Police Officer David Mascarella is back on the job after causing a 2020 crash that severely injured Riordan Cavooris, then 2. NewsdayTV's Andrew Ehinger and Newsday investigative reporter Paul LaRocco have the story. Credit: Newsday/Kendall Rodriguez; Jeffrey Basinger, Ed Quinn, Barry Sloan; File Footage; Photo Credit: Joseph C. Sperber; Patrick McMullan via Getty Image; SCPD; Stony Brook University Hospital

'It's disappointing and it's unfortunate' Suffolk Police Officer David Mascarella is back on the job after causing a 2020 crash that severely injured Riordan Cavooris, then 2. NewsdayTV's Andrew Ehinger and Newsday investigative reporter Paul LaRocco have the story.

Suffolk Police Officer David Mascarella is back on the job after causing a 2020 crash that severely injured Riordan Cavooris, then 2. NewsdayTV's Andrew Ehinger and Newsday investigative reporter Paul LaRocco have the story. Credit: Newsday/Kendall Rodriguez; Jeffrey Basinger, Ed Quinn, Barry Sloan; File Footage; Photo Credit: Joseph C. Sperber; Patrick McMullan via Getty Image; SCPD; Stony Brook University Hospital

'It's disappointing and it's unfortunate' Suffolk Police Officer David Mascarella is back on the job after causing a 2020 crash that severely injured Riordan Cavooris, then 2. NewsdayTV's Andrew Ehinger and Newsday investigative reporter Paul LaRocco have the story.