Pennsylvania officials are warning against a surge in ticks this summer, including black-legged ticks, which carry Lyme disease, as well as invasive ticks from the American South and Asia.

The state’s acting physician general, Denise Johnson, said this is the time of year when ticks are most active, noting that “this year we’re seeing more than ever.”

She said there’s been an increase in tick bites as well as Lyme disease.

“In Pennsylvania, every single county within the state does have ticks that carry Lyme disease,” Johnson said earlier this week. “And then ticks also can carry other diseases. ... This summer don’t let a tick make you sick.”

Officials say that not only are there more ticks, but also more people started exploring the outdoors during the pandemic, flocking to many of the commonwealth’s 121 state parks. That has led to more tick encounters — and bites.

» READ MORE: Interest in Pennsylvania’s state parks has only grown even as pandemic restrictions lift

They said tick populations can vary from year to year, fluctuating according to environmental factors such as temperature, humidity, rainfall, and the availability of hosts.

Black-legged ticks, also called deer ticks, spread the bloodborne infection Lyme disease, now the most common vector-borne disease in the country. Symptoms are marked by fever, headache, fatigue, and a characteristic bull’s-eye rash. If not treated, the infection can spread to joints, the heart, and the nervous system.

The same ticks also spread the anaplasmosis bacteria and the Powassan virus, both of which share similar symptoms of fever, headache, vomiting, and weakness.

State scientists with the Department of Environmental Protection and Department of Health collected 5,000 adult black-legged tick nymphs this year as part of an annual survey. DEP Secretary Patrick McDonnell said 58% of those were carrying Lyme disease.

Last year, between April and August, scientists collected 1,200.

“We’re on a path to double that this year,” McDonnell said. “We’re currently almost 500 nymphs ahead of where we were last year and still have the month of August to go.”

McDonnell said most people get Lyme disease from nymphs because they are so small, about the size of a poppy seed, and hard to spot.

But Pennsylvania is also experiencing a trend seen in New Jersey over the last few years: the emergence of a variety of other ticks on the move from elsewhere.

» READ MORE: N.J. has at least 11 tick species, and some are making us sick

“We’re starting to see some additional ticks ... like the Asian long-horned and the lone star that are starting to become established within the state,” McDonnell said. “So this is an issue that is going to be with us going forward.”

Cindy Adams Dunn, secretary of the Department of Conservation and Natural Resources, said her husband has had Lyme disease, and advises people going outdoors to wear lightweight long sleeves and long pants tucked into boots.

“It is always important to take preventative measures so you can enjoy the mental and physical health benefits of being in the outdoors, especially with regard to ticks,” Dunn said. “As tick-borne diseases are becoming more prevalent in Pennsylvania, it is critical to be aware of the risks and be prepared.”

She said people can use EPA-approved repellents, such as permethrin, a nontoxic insecticide that can be sprayed on clothing and boots.

Officials also recommend people avoid areas dense with shrubbery or tall grass where ticks like to hide, and immediately check themselves and pets as soon as they return home. They advise taking a shower as soon as possible, and run clothing and gear in a dryer to kill any ticks.