A tropical disease that can cause 'chronic ulcer-type lesions' is spreading across the US through sand flies

• Cutaneous leishmaniasis is a tropical disease previously unseen in the United States.
• In the past several years, cases have appeared in states like Texas and Arizona.

After strange bumps appeared on her patients in Texas, a dermatologist discovered they suffered from a tropical disease rare in most western countries — and it's spreading through the United States on minuscule bugs called sand flies.

The disease is cutaneous leishmaniasis, one of three main forms of leishmaniasis, per the World Health Organization. The Centers for Disease Control and Prevention presented research in October suggesting cutaneous leishmaniasis can regularly occur in the United States.

Cutaneous leishmaniasis is contracted after a bite from a sand fly and causes skin lesions and ulcers on the skin. Depending on the person, the disease could leave life-long scarring, per the WHO.

The lesions develop within weeks or months of a sandfly bite, and can be painful for some infected people. Others have no symptoms at all, per the CDC.

The CDC estimates that between 700,000 and 1.2 million new cases of cutaneous leishmaniasis are found worldwide per year, and are more common in tropical regions. In the US, cases have been identified in Arizona, Texas, and Oklahoma, per the CDC.

More cases have been identified in the country because of climate change, per NPR. An infectious diseases physician told NPR that as temperatures heat up, the sandfly can expand north, away from tropical areas, and expose more people.

Bridget McIlwee, the dermatologist who found the disease on her patients in 2014, told NPR she was initially "shocked" at her discovery.

"In medical school, we're taught that this is a tropical disease, something that you see in immigrants, military returning from deployment, people who went on vacation to South America or Asia or Africa," McIlwee said to NPR.

Most alarmingly, there isn't much people can do to prevent the disease, per the CDC. There isn't a vaccine or any kind of drug that treats it — the only real course of action is to avoid a sandfly bite in the first place.

The CDC advises people to keep as much skin covered as possible with clothing, wear strong insect repellent that contains the chemical DEET, and avoid outdoor activities from dusk to dawn.

Despite the fact that the disease is endemic, though, relatively few cases have been identified in the United States, per the CDC.