Delco West Nile case is the sixth reported this year in the Philly region

A person in Delaware County has tested positive for West Nile virus, local health officials said Tuesday, becoming the sixth person diagnosed with the mosquito-borne illness across the area this year.

West Nile virus is most commonly spread during the summer and early fall. While most people infected never develop symptoms, about 20% develop a fever and other flulike symptoms, including body aches, joint pains, headache, diarrhea, vomiting, and rashes.

Most recover fully, though fatigue can linger for months.

Fewer than 1% of people develop severe illness, resulting in inflammation of the brain and spinal cord, according to the Centers for Disease Control and Prevention. Deaths are rare, and none have been reported in the city of Philadelphia this year.

Last year, there were four deaths in the Philadelphia region — three in Montgomery County and one in Delaware County, according to state data posted online, which does not indicate whether or not deaths have occurred this year.

The city of Philadelphia regularly tests mosquitoes for the virus at various sites. The first infected mosquitoes of the season were found in June, near Pennypack Park in Northeast Philadelphia.

This year, the rate at which mosquitoes are testing positive is higher than normal, compared to the last couple of decades. Still, this year is comparable to more active West Nile virus seasons observed in 2010, 2018, and 2022.

“Increased risk for human infection will continue in Philadelphia until the first hard frost occurs,” according to a webpage maintained by the Philadelphia Department of Public Health.

This year’s six total cases in people across the Philadelphia region include one case each in Philadelphia, Delaware, Montgomery, and Chester Counties and two in Bucks County.

Last year, Pennsylvania recorded 60 cases across 20 counties, including nine in the city of Philadelphia.

There is no specific treatment for the virus, making it extra important for people to protect themselves from infection.

Health officials recommend warding off mosquito bites by applying insect repellent with DEET, picaridin, or oil of lemon eucalyptus, and wearing long-sleeved shirts and pants.

To help control the spread of mosquitoes, residents should also look out for areas where mosquitoes like to breed: buckets, trash cans, bottle caps, and anywhere else water can collect. Local health departments across the Philadelphia area actively spray for mosquitoes with insecticides and eliminate breeding sites.

“Make daily inspections for standing water sources on your property a part of your family’s routine,” Delaware County Health Department Director Lora Siegmann Werner said in a Tuesday news release.