Why Your Risk of Parasites Goes Up in the Summer, and How to Stay Safe

Summer is an especially vulnerable time for getting a parasitic infection, according to doctors who specialize in treating infectious diseases.

“As temperatures get warmer, parasites are able to complete their developmental life cycle and infect humans,” says professor Thomas Russo, MD, chief of infectious disease at the University at Buffalo in New York. “But humans are also much more likely to be outdoors and interact with certain parasites in the summer.”

Swimming can raise the risk of contracting certain parasites, too, says Amesh A. Adalja, MD, a senior scholar at the Johns Hopkins Center for Health Security in Baltimore.

Fortunately, common sense precautions can help you stay safe during summer activities where you’re likely to encounter parasites.

Swimming in Pools, Lakes, and Rivers Can Raise Parasite Risk

The most common type of parasite you can pick up while swimming is giardia, says Dr. Adalja.

But there are other parasitic infections you can pick up in the water, including cryptosporidium, which causes watery diarrhea, and Naegleria fowleri, sometimes called brain-eating amoebas.

“Naegleria infections are exceedingly rare, but can occur with lake and pond water exposure,” Adalja says. Cryptosporidium infections usually happen after a person accidentally swallows water while swimming, while Naegleria fowleri infections typically happen after infected water goes up the nose, Dr. Russo explains.

“This is more common in Michigan, around the Great Lakes,” Russo says.

How to Swim Safely

To lower your risk of contracting a parasite while swimming, “Try to avoid getting water up your nose and in your mouth,” Russo says. It can also be helpful to rinse off after swimming, ideally with soap and water, he says.

Hiking Can Raise the Risk of Parasitic Infections Spread by Ticks

While ticks are well-known for spreading Lyme disease, which is a bacterial infection, they can also cause a parasitic infection called babesiosis, Adalja says.

How to Hike Safely

The best way to lower your risk of babesiosis and other tickborne infections is to try to prevent tick bites, Russo says. He recommends:

• Applying repellents with DEET to your skin and clothes.
• Staying on clear trails and avoiding tall grasses and brush.
• Wearing long socks, pants, and long-sleeved shirts.

If you’ve been hiking, “Don’t forget to do tick checks afterward,” Russo says.

Undercooked Meat at Barbecues and Picnics Can Harbor Parasites

Eating undercooked meat can cause toxoplasmosis if the food contains the microscopic parasite Toxoplasma gondii. “Toxoplasmosis is very common with about 10 percent of the U.S. population infected through ingestion of undercooked meat and contaminated fruit and vegetables,” Adalja says.

How to Picnic and Barbecue Safely

Russo recommends making sure that your meat is thoroughly cooked before eating it. It’s also important to wash all produce well, he says. “Don’t forget to wash your hands,” he adds.

The Takeaway

• Parasites in water, on land, and in food can make you sick during the summer.
• Avoid swallowing water or getting it up your nose while swimming to lower your risk of giardia and other waterborne parasites.
• Stay on marked hiking paths, use insect repellant, and wear long sleeves and pants to reduce your risk of the tickborne illness babesiosis.
• To prevent parasitic infections at picnics and barbecues, only eat fully cooking meat, wash produce, and keep your hands clean.