West Nile virus is transmitted from birds through bites by the Culex pipiens mosquito.
Since the beginning of the year, 60 cases, 16 people are still in the hospital, four of them in intensive care.
Aerial spraying has also occurred over agricultural areas outside the city limits.
"The amount of virus we are detecting in mosquitoes is well above the historical average for this time of year and is also occurring earlier in the season than the average", Mark Clifton, the agency's director, said in the release.
Mosquitoes are most active at dawn and dusk.
Approximately 80% of people infected with WNV experience no symptoms, but up to 20% can develop a mild illness, called West Nile fever.
Mosquito pools in every county in New Jersey except for Passaic have tested positive for the virus.
Epidemiologist Elizabeth Schiffman says the majority of people often don't have any symptoms, they may not even know they're infected.
'Until the state's first hard frost, whether it's for work or play, being outside means there's a risk for West Nile virus'. Most people who are infected with WNV do not have any symptoms; however some can develop a fever with other symptoms like headache, body aches, joint pains, vomiting, diarrhea, or rash. "The best way to avoid the disease is to reduce exposure to and eliminate breeding grounds for mosquitoes".
Install or Repair Screens - Some mosquitoes like to come indoors. Eliminate all sources of standing water by emptying flower pots, old vehicle tires, buckets and other containers. Use a repellent with DEET (N, N-diethyl-m-toluamide), permethrin, picaridin (KBR 3023), IR3535 or oil of lemon eucalyptus [p-methane 3, 8-diol (PMD)] according to the instructions on the product label. Report swimming pools that are not being properly maintained by contacting the Sacramento-Yolo Mosquito & Vector Control District at 1-800-429-1022 or www.fightthebite.net/pool-program. Do not apply under clothing, to wounds or irritated skin, the hands of children, or to infants less than two months old.
Use mosquito netting when sleeping outdoors.
"Make sure to fix or install window and door screens to keep mosquitoes from entering your home".