It's been confirmed that the mainland U.S. is now home to a disease once thought to only exist in tropical climates, as NPR has reported. Leishmaniasis has joined other diseases in spreading to new places as the warming planet opens up new populations to these diseases.
What's happening?
According to the World Health Organization, there are between 700,000 and one million new leishmaniasis cases a year, almost exclusively in tropical areas of the planet and, until recently, most certainly not in the contiguous United States.
But in 2014, a doctor in central Texas saw a three-year-old patient with unusual bumps on his ear who tested positive for the parasitic disease, per NPR.
"I was shocked," said Bridget McIlwee, the doctor who saw the young patient, "because 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."
Following that diagnosis, McIlwee and her colleagues investigated the presence of leishmaniasis in the U.S., publishing their findings in 2018. This led the Centers for Disease Control and Prevention to investigate, which reinforced those findings, suggesting that the leishmaniasis parasite has likely been present in the U.S. for years.
Leishmaniasis is primarily spread by sand flies. Most of the cases in the U.S. have been reported in Texas, but Texas is the only state that requires reporting of the disease to health authorities, so the actual spread of the disease is hard to track, NPR reported.
According to the WHO, only a small fraction of patients infected by the parasites that cause leishmaniasis will eventually develop the disease. And while there are treatments for leishmaniasis, they're not without issues, either.
"There are several [treatments], but they tend to be pretty severe and people may have side effects," Mary Kamb, a medical epidemiologist at the CDC, told NPR. "And if they need to take treatment by mouth, they tend to have a long treatment period of about 28 days."
"There's no effective vaccine against leishmaniasis, and there aren't any drugs that people can take to prevent it," she continued, adding that the only things that can help prevent it are wearing clothing that covers the arms and legs and, when traversing an area where there might be sand flies, using insecticide.
Why is the spread of leishmaniasis in the U.S. concerning?
Leishmaniasis is the latest disease to have spread to new areas of the world as the planet continues warming. In a recent report, experts predicted that the West Nile virus, historically found in warmer regions, will travel farther and become more common than ever.
That report came on the heels of another study that showed that more areas of the planet are experiencing tropical weather, and that trend will continue.
The warmer temperatures will cause more extreme weather and population shifts, but not just among humans. Plants, mammals, and insects will also find themselves moving farther north than they would have in the past, and with them, diseases new to those areas.
What's being done about the spread of leishmaniasis in the U.S.?
The CDC is raising awareness among clinicians that leishmaniasis is now present in the U.S., despite what they may have been taught in medical school.
"Every medical textbook, whether it's Dermatology or Principles and Practice of Infectious Disease, teaches that this is a tropical disease," McIlwee told NPR blog Goats and Soda. "So there's a huge disconnect between the clinical reality and what's being taught in medical schools."
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