While the risk of malaria transmission in the US is normally low, risk increases: (1) in US regions where Anopheles mosquito vectors are found; (2) when local climatic conditions allow the Anopheles mosquito to survive throughout the year; and (3) in US regions with frequent travelers from malaria-endemic countries. The risk of malaria transmission affects all people, including infants and children. In June 2023, five cases of malaria were reported from mosquitoes in the United States, and this prompted the Centers for Disease Control and Prevention (CDC) to issue a Health Alert Network (HAN) advisory. Through the HAN advisory, CDC urged clinicians to consider a malaria diagnosis in any person with fever of unknown origin regardless of their travel history. As most cases of malaria in the U.S. are imported among travelers from malaria-endemic countries, clinicians should continue to routinely obtain travel history and consider malaria in a symptomatic traveler. Suspected or confirmed locally acquired malaria is a public health emergency and should be reported immediately to your state, territorial, local, or tribal health department.
What is the epidemiology of malaria?
Caused by the parasite Plasmodium sp and transmitted to humans by bite of mosquitoes (Anopheles sp).
Malaria is endemic in several tropical and subtropical countries. Malaria is not endemic in the US and occurs primarily in individuals who contract the disease while traveling to endemic countries. However, there have been locally acquired malaria cases reported in Florida and Texas.
How does malaria present in children?
In children, malaria often presents with non-specific symptoms that mimic other common childhood illnesses, such as gastroenteritis, meningitis, or pneumonia.
Typical manifestations include high fever with chills, headache, malaise, weakness, myalgia, fatigue, nausea, vomiting, and diarrhea.
Complications may include anemia and jaundice, and in severe cases, neurological symptoms such as dizziness, confusion, disorientation, or coma may occur. These severe manifestations are less common with Plasmodium vivax, the species most frequently associated with locally acquired cases, although a locally acquired case of P. falciparum malaria was reported in Maryland in August 2023.
The incubation period varies by species: symptoms may develop as early as seven days after being bitten by an infectious mosquito or as late as several months after exposure. Some parasite species can remain dormant in the liver for months or even years, delaying the onset of illness until long after the initial infection.
How is malaria transmitted?
Most malaria cases have occurred through the bite of an infective female Anopheles mosquito to a human. Rarely, malaria may be transmitted congenitally from mother to fetus or to the neonate at birth, through blood transfusions, organ transplantation, or through unsafe needle-sharing practices. Mosquito activity can increase as temperatures increase, and infected mosquitoes can multiply rapidly in areas that experience “monsoon season” and/or flash floods after heavy rainstorms. Mosquitos potentially carrying diseases such as malaria can reproduce rapidly in standing water, where small children and animals can be exposed. CDC – Malaria – About Malaria – Malaria Transmission in the United States
Who are considered high-risk patients?
Individuals without prior immunity to malaria, young children, pregnant women, and immunocompromised patients are at highest risk for severe disease. Malaria in pregnant women is associated with high risks of both maternal and perinatal morbidity and mortality. Malaria parasites sequester and replicate in the placenta. Pregnant women are three times more likely to develop severe disease than non-pregnant women who acquire malaria in the same geographic area. Malaria infection during pregnancy can lead to miscarriage, premature delivery, low birth weight, congenital infection, and/or perinatal death. Find more information here.
How is malaria diagnosed?
Blood smear microscopy remains the most important method for malaria diagnosis. This is a rapid test with results available in less than 24 hours. Microscopy of a blood smear can provide immediate information about the presence of parasites, allow quantification of the density of the infection, and allow determination of the species of the malaria parasite—all of which are necessary for providing the most appropriate treatment. If the initial blood smear is negative but index of suspicion of malaria remains high, repeating the blood smear once a day for the next 2 days may be helpful. Rapid diagnostic tests (RDTs) are immunochromatographic tests that most often use a dipstick or cassette format and provide results in 2–15 minutes. RDTs offer a useful alternative to microscopy in situations where reliable microscopic diagnosis is not immediately available. Although RDTs can detect malaria antigens within minutes, they have several limitations. RDTs cannot distinguish between all Plasmodium species that affect humans, and they might be less sensitive than expert microscopy or PCR for diagnosis. PCR tests also are available to detect malaria parasites. These tests are more sensitive than routine microscopy, but results are not usually available as quickly as microscopy results. Find more information here.
What is the best way to prevent malaria?
Malaria can be fatal even when treated, which is why prevention is always preferable to treating infections after they occur. The primary method of malaria prevention is to avoid mosquito bites. Anopheles mosquitoes primarily feed at night with transmission occurring mostly between dusk and dawn. Prevention strategies when traveling to countries with endemic malaria include personal protective measures such as using insecticide-treated bed nets, wearing clothes that minimize exposed skin, and applying mosquito-repelling chemicals. Not all mosquito repellents are safe for all children. The American Academy of Pediatrics provides guidance for how caregivers can choose a safe and effective insect repellent for their child.
All travelers to malaria-endemic regions should be prescribed antimicrobial prophylaxis. Prophylaxis is not necessary for people in the US, even in areas where local transmission of malaria has been identified. All prevention regimens involve beginning the medication before departure, taking the medication while in the high-risk area, and continuing the medication for a defined period after travel has ended. These regimens should be used concurrently with personal protective measures. Clinicians can remind patients and their families to prevent mosquito bites and control mosquitoes at home to protect them from mosquito-borne illnesses. Find more information here.
How is malaria treated in children?
Prompt diagnosis must be followed by immediate treatment. The treatment regimens depend on the infecting Plasmodium species, the patient’s clinical status, drug-resistance status and previous use of antimalarials. Presumptive treatment should be reserved for extreme circumstances, such as strong clinical suspicion of severe disease in a setting where prompt laboratory diagnosis is not available. Once diagnosed, malaria must be treated immediately. If not treated promptly, malaria may progress to severe disease, a life-threatening stage, in which mental status changes, seizures, renal failure, acute respiratory distress syndrome, coma, and death may occur. Clinical guidance is provided from the CDC. A CDC Malaria Hotline can be reached at 770-488-7788 or toll-free at 855-856-4713 from 9 a.m. to 5 p.m. Eastern Time. After hours, on weekends, or on holidays, call the CDC Emergency Operations Center at 770-488-7100 and ask the operator to contact the subject matter expert on call for the Malaria Branch.
Information for parents and families
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