Nassau County on Friday reported three more human cases of West Nile virus, making the total number on Long Island so far this year 13.
One case involves a resident older than 30 in the Town of Oyster Bay. The resident is "hospitalized and is recovering," the Nassau health department said in a statement.
The two other cases involve residents older than 50 in the Town of Hempstead. One is "hospitalized and is recovering" and the other is hospitalized, officials said.
Nassau has reported nine West Nile cases so far this year.
Four people infected with the disease -- all adults -- are in Suffolk, including three new cases announced Monday involving Town of Islip residents, all younger than 55.
No deaths related to the virus have been reported this year.
Last year, Suffolk County reported one human case of West Nile virus and four cases in both 2011 and 2013; 14 were reported in 2012 and 25 cases in 2010, a year in which the virus killed three.
Some mosquito bites can transmit West Nile to humans, with mosquitoes picking up the virus by feeding on infected birds. In some cases, the virus causes serious neurological illnesses that can lead to health conditions or death.
Two new mosquito samples have tested positive for West Nile virus in Suffolk, making the total now 198 there, county health officials reported Friday.
The new samples, both Culex pipiens-restuans, were collected Sept. 30 in Oakdale and Setauket, the Suffolk health department said.
Nassau County reported 61 positive mosquito samples as of Friday, according to health officials.