According to the Centers for Disease Control and Prevention (CDC), about 2,000 cases of malaria are diagnosed in the United States each year. The vast majority of cases in the United States are in travelers and immigrants returning from countries where malaria transmission occurs, many from sub-Saharan Africa and South Asia.
However, for the first time in 20 years, malaria has spread from mosquitoes to humans inside the U.S., the Centers for Disease Control and Prevention (CDC) has warned.
Four cases of mosquito-transmitted Plasmodium vivax malaria have been reported in Florida within the last two months, and a single case was also found in Texas. All patients were said to be improving after receiving treatment.
The CDC said in a health advisory that Anopheles mosquitoes, which are found throughout many regions of the country, “are capable of transmitting malaria if they feed on a malaria-infected person.” However, it stressed, the risk of catching malaria in the U.S. is “extremely low.”
Before Covid, some 2,000 malaria cases were reported in the US each year, with almost all coming from travelers who had visited malarial countries. Infections led to between five and 10 deaths annually.
The last time malaria transmission was reported in the U.S. was in 2003, when eight cases were detected in Palm Beach, Florida.
The vast majority of the world’s 240 million annual cases are spread by the bite of an infected female mosquito. In rare cases, the disease can also be transmitted from a mother to her unborn baby, through blood transfusions or from sharing needles.
Symptoms can include fever, chills, headache, muscle pain, fatigue, nausea, vomiting and diarrhea, according to the CDC. Symptoms typically begin between 10 days and four weeks after infection, although they can manifest up to a year later.
The CDC says patients suspected to have malaria should undergo blood tests and rapid diagnostic tests where available. Treatment includes taking antimalarial drugs such as chloroquine or atovaquone and proguanil, depending on where the infection was thought to have originated.
If untreated, malaria can progress to become a severe disease, leading to complications including seizures, kidney failure, acute respiratory distress syndrome, coma and potentially death.
The best way to protect yourself from malaria is by preventing mosquito bites. The CDC recommends using insect repellent registered with the Environmental Protection Agency, wearing loose-fitting, long-sleeved shirts and pants, using mosquito screens on windows and doors and getting rid of items in which water can collect where mosquitoes could lay their eggs.
