New Jersey health officials report that the state has seen its first case of West Nile virus in a human this year.

Officials say that the case was confirmed in Hunterdon County and that two other potential cases are under investigation.

Mosquito pools in every county in New Jersey except for Passaic have tested positive for the virus. Officials say that 284 pools tested positive — almost 100 more than at this time last year. Bergen County may be the hardest hit, with 20 of those pools located there.

More than 100 people across the country have tested positive for the illness this year.

Health officials say that most people infected with the virus do not see any symptoms. The Centers for Disease Control and Prevention say that one in 150 people infected develop a serious illness that affects the central nervous system. Symptoms include high fever, convulsions and muscle weakness, and the illness can put someone in a comatose state. Of those who develop a serious illness from the virus, one in 10 die, according to officials.

Several counties around the state are spraying for mosquitoes to reduce the number that could potentially carry the virus. Residents are urged to keep pets indoors overnight while spraying is underway.