Traveling to Southern Europe? Here’s what to know about a deadly parasite active there.

Are you planning a vacation to Spain, Italy, France, Greece, or another country along the Mediterranean?

If so, you should know about a parasite that puts travelers at risk of a rare disease, called “visceral leishmaniasis,” that can be deadly when untreated. The parasite — leishmania — is transmitted by a bite from an infected sandfly. It can lie dormant in the body for years, then later cause severe illness, including persistent high fever.

A 34-year-old South Jersey resident, Louis-Hunter Kean, died from it in late 2023 after doctors at two South Jersey medical systems and later at Penn Medicine missed the diagnosis. His symptoms developed about a year after he vacationed in Tuscany, where parasitic disease experts now believe he was infected.

» READ MORE: A South Jersey man died from leishmania in 2023

“Leishmania in the U.S. is underappreciated,” said Joshua A. Lieberman, assistant director of the molecular microbiology clinical laboratory at University of Washington in Seattle. “We want to get the word out that there’s a lot more of it than we think.”

Parasitic disease experts say most American doctors don’t know enough about leishmania. Here’s what you should know about leishmania:

Worldwide, there are more than a dozen species of leishmania that cause three different diseases in humans.

Visceral leishmaniasis is caused by the most deadly species. At risk are travelers to Southern Europe, Brazil, East Africa, India, and military personnel who were deployed to Afghanistan and Iraq. Its primary symptom is fever, along with an enlarged liver and spleen, weight loss, and a low blood cell count. Each year, an estimated 50,000 to 90,000 new cases are reported globally, according to the World Health Organization (WHO).

The majority of healthy people who get infected never experience symptoms or sickness. However, the parasite can cause severe illness in small children, senior citizens, and people who are malnourished or immunocompromised. It can activate decades after exposure.

Cutaneous leishmaniasis is the most common and less dangerous form of the disease. This species is present in the countries that also have visceral leishmaniasis, as well as in Israel, Mexico, Central and South America — and in a few U.S. states, including Texas, Oklahoma, and Arizona. More than 80 cases have been reported in the U.S. since 2017, though experts believe that’s an undercount, according to a recent study published in the digital journal JMIR Dermatology.

People with active cases first see small, red bumps on the skin that can develop into skin ulcers, which may ooze or scab. These symptoms typically appear within weeks or months after exposure, but ulcers can surface years later. Worldwide, an estimated 600,000 to 1 million cases occur each year, according to the WHO.

“If you’re traipsing through the rain forest in Central America, you’re at huge risk,” said leishmania expert David L. Sacks, an immunologist and senior investigator with the National Institutes of Health (NIH). “We see patients all the time at the NIH hospital who have the cutaneous form from traveling.”

Mucosal leishmaniasis is most commonly found in parts of the Amazon basin, specifically Bolivia, Peru, and Brazil. Symptoms usually start as a skin sore, which can advance to the nose, mouth, or throat and cause severe facial disfigurement. It can be life-threatening.

All three types are treatable with antiparasitic and antifungal medications.

Some forms of cutaneous leishmaniasis will heal on their own.

More than 90% of patients with visceral leishmaniasis will die without treatment. An estimated 20,000 to 50,000 people die from it each year, according to research published in the academic journal Tropical Diseases, Travel Medicine and Vaccines.

An exact number of cases is unknown. The federal government does not require doctors to report the disease to the Centers for Disease Control and Prevention. Texas is the only state that requires medical providers to report cases to the state health department.

The CDC identified 1,222 cutaneous leishmania cases in the U.S. from 2005 to 2019.

There are no vaccines or drugs for prevention, but people can take steps to protect themselves when visiting areas where the parasite is circulating.

Sandflies are most active from dusk until dawn, so consider staying indoors during that time. Wear long-sleeved shirts and long pants, and socks that cover ankles. Apply insect repellent, preferably with DEET, to clothing and exposed skin. Sandflies can slip through window and door screens, so it’s best to stay in accommodations with air-conditioning or sleep under insecticide-treated bed nets.

People who are immunocompromised may want to avoid travel to regions with leishmania.

Also, if you experience symptoms, especially a high fever that won’t go away, provide your doctor with a thorough travel history, going back decades.