Twenty years after eight cases of malaria were identified as having been locally transmitted in Palm Beach, Florida, the mosquito-borne illness has infected four people in Florida and one in Texas via local transmission, prompting the Centers for Disease Control and Prevention (CDC) to issue its recent alert. Perhaps more than some of the other illnesses in the news over the past several months, “this one has struck a chord,” says Vincent Hsu, MD, infectious disease specialist and infection control officer for AdventHealth.
“We don’t think of malaria as an endemic disease,” Dr. Hsu says. “People are familiar enough with it to know that it’s dangerous. And now they may be recognizing that it’s no longer an exotic disease, that it’s at our doorstep and that you don’t have to travel to get it. I think that strikes fear.”
While he stresses that there is no need to panic, Dr. Hsu believes the recent outbreak provides an opportunity to emphasize the importance of protecting against bites from mosquitoes that carry not only malaria parasites but also can carry viruses such as West Nile and dengue. However, as the CDC points out, “not everyone infected with a mosquito-borne germ gets sick.” And, as Dr. Hsu adds, “the true risk is low. Millions of us get bitten by mosquitoes all the time.”
Malaria is not contagious via the usual person-to-person contact, though it can be transmitted from pregnant mom to baby, through blood transfusions and shared needle use. Mosquitoes must bite an infected person to spread the disease. According to the CDC, about 2,000 cases of malaria are diagnosed in the U.S. each year, the majority of those in travelers and immigrants returning from parts of the world where malaria transmission occurs. Globally, the World Health Organization estimated there were 241 million clinical cases of malaria in 2020 and 627,000 deaths, most of them children in Africa.
Interestingly, the CDC has its roots in the control of malaria. The Communicable Disease Center was created on July 1, 1946, as a new component of the U.S. Public Health Service. Succeeding the Office of Malaria Control in War Areas, which was established in 1942, the center was located in Atlanta because the South was the area of the country with the most malaria transmission. Malaria was considered eliminated in the U.S. in 1951.
"The true risk is low. Millions of us get bitten by mosquitoes all the time."
The winged culprit at the center of the Florida and Texas cases is the Anopheles mosquito, which has provided transport for P. vivax, one of four blood parasites of the genus Plasmodium known to infect humans. Though malaria can be fatal, the P. vivax strain is not nearly as severe as the others, Dr. Hsu says. Malaria is not easily distinguishable from other bacterial and viral infections that cause fever, chills and other flulike symptoms, and requires a special blood test specific for parasites to confirm.
“There are so many things that can cause a fever and, if this trend continues, we have to add another bug to that thought process,” says Dr. Hsu. As with any infectious disease, he stresses, “We want to be able to identify it as quickly as possible,” which means clinicians quickly will have to become well-versed in something they’re not used to seeing. In the case of malaria, for which safe and effective treatments exist, “if it’s not treated, the parasites will continue to multiply,” which can lead to more severe complications such as alterations in consciousness and anemia.
The recent cases underscore the need for people to take the usual precautions when it comes to fending off mosquitoes, including perhaps brushing up on their knowledge of mosquito habits. The anopheles mosquito that carries the malaria parasite, for example, mostly prefers nighttime meals while other species, carrying viruses that cause diseases such as dengue fever or Zika, may be active throughout the day.
“I think this is a good warning for us,” Dr. Hsu says. “Given the warming climate, given the travel and migration that we see, we probably are going to see more endemic malaria cases. On the good news front, a safe and effective malaria vaccine has been developed, but it’s going to be many years before we’ll be able to vaccinate the population that needs to be vaccinated to quell malaria.”
For those in a summer vacation frame of mind, Dr. Hsu offers these words of advice: “Use simple common-sense strategies to reduce the risk of getting bitten, which reduces your risk of getting a mosquito-borne disease and potentially spreading it to others. By being cautious and being aware, you can have a great time without upending your plans.”