Local Malaria Cases Just Popped Up In The U.S. Here's What You Need To Know.

The first local cases of malaria in decades have cropped up in the U.S. and are being actively monitored by health officials, according to a new health advisory issued by the Centers for Disease Control and Prevention .

Four cases of locally acquired malaria were recently identified in Florida ’s Sarasota County, and health officials say they are unrelated to a fifth case confirmed in Texas . All five patients have been treated and are currently improving, the agency said.

It’s the first time since 2003 that any cases of locally transmitted malaria have been documented, with the disease having been considered eliminated in the U.S. by 1951 . Prior to the COVID-19 pandemic, about 2,000 Americans were diagnosed with malaria each year, but all of those cases were linked to international travel to a malaria-endemic country .

When people who contract malaria abroad return to the U.S., local Anopheles mosquitoes can bite them and become infected with the malaria-causing parasites. The new cases were transmitted within U.S. borders by mosquitoes carrying such a parasite.

“With climate change and rapid travel, Anopheles mosquitoes with the malaria causing parasites are expected to be a bit more common, especially in parts of the U.S. that are warmer, like Florida and Texas,” said Dr. Megan Coffee , an assistant professor of population and family health at Columbia University’s Mailman School of Public Health.

The cases are unusual, and officials say the risk of widespread malaria transmission in the U.S. is still relatively low. However, there’s still a threat of more cases, as the CDC and other statewide organizations have issued public health alerts warning physicians, public health authorities and the general public about the risk.

How Malaria Spreads — And How You Can Limit Your Risk

Malaria is a vector-borne disease, which means it spreads through another organism — in this case, an infected female Anopheles mosquito.

“There are five parasite species that are known to infect humans. Of these, Plasmodium falciparum and Plasmodium vivax (both are human-only species), are responsible for most of the disease worldwide,” said Dr. Michelle Hsiang , a pediatric infectious diseases physician and the director of research at the University of California, San Francisco’s Malaria Elimination Initiative.

Malaria can also be transmitted person-to-person through blood transfusions or from an infected pregnant person to their baby via the placenta, added Dr. John Swartzberg , clinical professor emeritus at the University of California, Berkeley’s school of public health.

In order to limit your risk, take precautions not to be bitten by mosquitoes: Sleep in rooms with screened windows, wear long protective clothing and use insect repellents on your skin, recommended Hsiang. The CDC recommends sticking with EPA-registered insect repellents , which includes options with proven, safe ingredients like DEET and Picaridin.

The CDC expressed concern about a possible rise in imported cases, too, because of increased international travel this summer. If you have plans to visit a malaria-endemic country , take preventative drugs prior to or during your trip under the guidance of a medical professional. Because of the risk of counterfeit medicines, the CDC says they should be bought in your home country before you travel. (A vaccine is not recommended for U.S. travelers at this time.)

Malaria Symptoms And Treatment

According to Hsiang, an infection may cause flulike illness symptoms. Infected people can have fever, chills, night sweats, headache, body aches or fatigue. They may also experience cough and diarrhea. 

If you traveled abroad recently and are experiencing these symptoms, it’s critical to seek medical attention right away. For a diagnosis of malaria, you may need to undergo a blood test, Coffee said, with samples analyzed for the parasite under a microscope. 

When it comes to treating malaria of any origin, there are many different types of drugs that are tailored to the type of parasite, severity of the illness and drug resistance, said Hsiang.

“The species P. vivax, detected in the Florida and Texas cases, can remain dormant in the liver following treatment of the acute infection, leading to relapsing symptoms weeks to months later. It is important that antimalarial drugs are started immediately as malaria left untreated can cause severe illness,” said Dr. Michael Cappello , a pediatric infectious disease physician at Yale Medicine.

In 2020, an estimated 627,000 people worldwide  died of malaria , with most of those living in sub-Saharan Africa, an area with high transmission. Fortunately, if malaria is detected and treated early on and appropriately, the symptoms can improve in about three days and be completely resolved in a matter of weeks.

While public health officials and clinicians are preparing for a possible increase in locally transmitted cases, don’t panic. But if you are traveling to a malaria-endemic country, take preventative measures and watch out for symptoms when you return to keep yourself and others around you safe.