Avoiding summer bites: A look at West Nile virus and Lyme disease in the Philly area

Public health agencies are tracking West Nile virus, the leading cause of mosquito-borne illness in the continental U.S., and Lyme disease, an illness caused by a bacteria that spreads through tick bites.

Both diseases are more common in the summer months, and what starts with a pesky bite could turn into a serious illness. One of the four West Nile virus deaths in Pennsylvania last year took place in Philadelphia.

Here is the current state of both illnesses in the Philadelphia area:

Most people infected with West Nile virus do not experience symptoms, but about one in five develops a fever, headaches, and overall fatigue.

In rare cases — about one out of 150 infections — the disease can be severe and even fatal, causing inflammation of the brain and spinal cord. People over the age of 50 are at higher risk of serious illness.

» READ MORE: How to prevent and treat mosquito bites

Mosquitoes carrying West Nile have been found this year in Philadelphia, Montgomery, Chester, Bucks, and Delaware counties. Delaware County reported its first positive mosquitoes last week.

So far this year, there have been no cases of West Nile in humans in Philadelphia, data from the city’s Department of Public Health shows, or the rest of the Commonwealth, state data shows.

New Jersey’s public dashboard of mosquito-borne illnesses doesn’t include data on West Nile virus.

The key to West Nile virus prevention is mosquito control. That means eliminating breeding grounds, such as any source of standing water, overgrown shrubberies, and tall grass. People should wear bug spray with at least 20% DEET, the insect-repelling chemical, if they walk through brush or tall grasses or in heavily wooded areas.

Lyme disease causes fever, chills, fatigue, and muscle aches. The bacteria’s hallmark sign is a circular rash at the site of a tick’s bite, though it doesn’t always develop.

In some cases, a person can later develop headaches and rashes elsewhere on the body. In severe cases, Lyme can lead to drooped facial muscles, arthritis, heart palpitations, and brain inflammation.

The source is the blacklegged tick, also known as the deer tick, which is common in Pennsylvania. And over the past decade, state health department workers have found deer ticks testing positive for Lyme in more than a third of regularly checked sites.

Nearly 5,000 cases of Lyme disease were reported across Pennsylvania so far this year, a state dashboard shows.

This does not include Philadelphia, which did not share current data on Lyme for this season, but has seen an increase over the past decade. The city reported 402 cases in 2023, the last year for which complete data were available.

» READ MORE: Lyme disease cases are on the rise. Here’s how to protect yourself from tick-borne illnesses.

In the Philly suburbs, Chester County has the highest number of Lyme disease cases among Pennsylvania residents, with 451 confirmed as of July 10.

In New Jersey’s Burlington County, there have been 112 cases as of July 10, while Camden and Gloucester had fewer than 100, according to N.J. state data.

Take the same steps to prevent Lyme as you would to guard against West Nile. In addition to using bug repellent and wearing long-sleeved clothes, check your body for ticks after spending time in nature.

If you see a tick, use tweezers to pull it off, and stay away from home remedies like smothering a tick in Vaseline. Once removed, wash the area where a tick was found with soap and water.