Malaria in the United States
Commentary
By Philip R. Fischer, MD, DTM&H
Source: Filler S, et al. Malaria surveillance—United States, 2001. MMWR Morb Mortal Wkly Rep. 2003;52(SS05):1-14.
Even though malaria infections still kill more than a million people each year, the disease itself appears to occur uncommonly among travelers. In this surveillance summary, the US Centers for Disease Control and Prevention (CDC) provide a vivid reminder that malaria still is a real problem for many travelers. A review of the CDC data stimulates discussion of several points that are useful reminders for travel medicine practitioners and their traveling patients. Interestingly, the CDC report contains similar data to that obtained in the United Kingdom, where approximately 2000 individuals are diagnosed with malaria each year.1
Malaria Still Happens
Some travelers think that malaria is "just for other people," such as the "poor" who reside in developing countries. People can become complacent when they haven’t actually experienced malaria themselves or had some personal acquaintance with the disease. The CDC report provides a stark reminder to the contrary. There were 1383 reported individuals who became ill with malaria in the United States during 2001. In addition, others became ill while overseas. Even though the exact number of Americans traveling abroad is unknown and only a small percent of them became ill with malaria, the incidence of malaria in the United States reminds us that this is not an uncommon problem. Cases occurred in Guam, Puerto Rico, the Virgin Islands, the District of Columbia, and 49 states; only South Dakota was spared.
Malaria Still Kills
Sadly, 11 individuals died of malaria in the United States during 2001. The fatal cases occurred in individuals aged 12-79 years and included 7 males and 4 females. Most had been to Africa and had been previously well. Ten of the 11 had P falciparum infections, and several had high-level (> 10%) parasitemia. Some died within hours of reaching medical care, but others died within days following their first medical contact. Despite attempts at good medical care and, and in some cases even with initially improving clinical and parasitologic courses, patients died. Malaria still kills, and it can kill seemingly healthy American travelers.
African Travel Accounts for Most US Malaria Cases
Two-thirds of malaria cases imported to the United States were in travelers returning from Africa. Two-thirds of African cases were from West Africa, as Nigeria (254 cases) and Ghana (179 cases) were the most commonly represented destination countries. This likely reflects, at least in part, the travel patterns of Americans. Most of the Asian cases were from the Indian subcontinent. Even "safer" areas, however, were not completely safe; fatal cases occurred after travel to Haiti and China.
Compliance with Chemoprophylaxis Might Have Prevented Most Cases
Among civilians with malaria, 60% had used no prophylaxis, and an additional 15% had used a chemoprophylactic regimen that was not recommended by the CDC. Half of the nonrecommended regimens included chloroquine for travel to areas where chloroquine resistance is already well known.
Two hundred cases of malaria occurred after recommended prophylaxis use. Of these, 37% were due to P vivax and 7% were due to P ovale. In at least a fourth of these cases, adherence to recommended prophylaxis dosing was incomplete, and about a third of these cases became symptomatic more than 45 days after arrival in the United States (suggesting relapsing infection rather than primary failure of prophylaxis). There was no evidence for new areas of chloroquine-resistant P vivax among these patients reported in 2001. For the cases of P falciparum following use of a recommended chemoprophylactic agent, there was clearly documented noncompliance in about one third of cases; the level of compliance was unknown for the other patients.
VFR Malaria was Common
Of 678 civilian travelers with malaria and a known purpose for travel, nearly half (333) were traveling to visit friends and/or relatives. Tourism accounted for 94 cases, and 82 cases occurred in missionaries and their dependents. There were 50 business travelers, and, interestingly, no cases among aircrew members or sailors. It is clear that potentially effective efforts to decrease the incidence of malaria in the United States should focus on preventive care for individuals traveling overseas to visit friends and relatives.
Pay Attention to Pregnant Women
Twenty-two cases of malaria were reported among pregnant women. This accounted for 5% of cases among women. Only 4 (18%) of the pregnant women reported taking prophylaxis even though 31% of nonpregnant women reportedly used prophylaxis. Realizing that the consequences of malaria can be more severe during pregnancy, efforts to provide prophylaxis should be emphasized rather than decreased during pregnancy.
There was also one case of congenital malaria2 reported in 2001. The mother, a native of Pakistan, previously had malaria that had resolved on chloroquine more than a year prior to delivery. She became symptomatic with malaria 10 days after delivery, and her newborn became febrile with P vivax parasitemia at 2 months of age. Both mother and baby recovered with standard chloroquine and primaquine therapy.
Avert Tragedy with Appropriate Diagnosis
Any case of malaria in the United States represents a failure of our preventive measures, and travel medicine practitioners have work to do in reaching and helping the traveling population. Deaths due to malaria, however, are particularly tragic—especially when they are associated with delayed diagnosis.
While games of "what if?" are not always productive, it is useful to consider the pediatric death reported by the CDC. It should serve as a reminder to all physicians to provide appropriate prophylaxis to travelers, to consider the travel history when caring for febrile patients, and to seek a diagnosis of malaria in a febrile-returned traveler. Helpful reviews of the prevention3 diagnosis, and treatment4 of malaria in children are being published in 2003.
The first fatal US case of malaria in 2001 was a 12-year-old boy who had lived in the United States for 10 years. In December 2000, he visited Nigeria for 3 weeks; chloroquine prophylaxis had been prescribed. On Jan. 11, 2001, he presented to a clinic with a 2-day history of fever with chills, fatigue, cough, and a single episode of vomiting. He was diagnosed to have an "upper respiratory infection complicated by nausea and vomiting" and was prescribed a cephalosporin antibiotic. Three days later, he collapsed, was transported to an emergency room, and died. Retrospectively, blood taken on Jan. 11 had 0.8% of red cells infected with P falciparum; by the day of death, he had a 14% parasitemia.
The CDC report provides a reminder about both the frequency and the seriousness of malaria in the United States. Travel medicine practitioners can use this report to upgrade their efforts to reach international travelers, to provide appropriate malaria prevention guidance and intervention, and to carefully diagnose illness in returned travelers.
Dr. Fischer is Professor of Pediatrics, Department of Pediatric & Adolescent Medicine, Mayo Clinic, Rochester, MN.
References
1. Spira AM. Assessment of travelers who return home ill. Lancet. 2003;361:1459-1469.
2. Fischer PR. Malaria and newborns. J Trop Pediatr. 2003;49:132-134.
3. Stauffer WM, et al. Traveling with infants and children. Part IV. Insect avoidance and malaria prevention. J Travel Med. 2003;10:225-240.
4. Stauffer WM, Fischer PR. Diagnosis and treatment of malaria in children. Clin Infect Dis. 2003; In press.
Even though malaria infections still kill more than a million people each year, the disease itself appears to occur uncommonly among travelers. In this surveillance summary, the US Centers for Disease Control and Prevention (CDC) provide a vivid reminder that malaria still is a real problem for many travelers.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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