US Malaria Cases at a 40-Year High

Lara C. Pullen, PhD

October 31, 2013

The Centers for Disease Control and Prevention (CDC) reports that there were 1925 cases of malaria in the US in 2011. This is the largest number of cases since 1971 and is evidence that malaria remains endemic in many regions.

Karen A. Cullen, PhD, and Paul M. Arguin, MD, of the Division of Parasitic Diseases and Malaria, Center for Global Health, CDC, in Atlanta, Georgia, summarized malaria surveillance data in the November 1 Morbidity and Mortality Weekly Report (MMWR). The 2011 surveillance data represent a 14% increase in malaria cases from 2010 and a 48% increase from 2008.

"Malaria isn't something many doctors see frequently in the United States thanks to successful malaria elimination efforts in the 1940s," said CDC director Tom Frieden, MD, MPH, in a news release. "The increase in malaria cases reminds us that Americans remain vulnerable and must be vigilant against diseases like malaria because our world is so interconnected by travel."

Infections are becoming more severe, with 14% of cases in 2011 classified as severe infections compared with 11% in 2010 (P < .0018). Five of the cases in 2011 were fatal.

The vast majority (1920) of the cases were imported.

Only 57 (6%) patients reported that they had followed and adhered to a chemoprophylactic drug regimen recommended by the CDC for the regions to which they had traveled.

More than two thirds (69%) of the cases were imported from Africa. Currently, airline crews comprise a very small proportion of malaria cases, although experts wonder if that may change as the number of daily flights to Africa increases.

Military personnel stationed in Afghanistan comprised 91 of the 2011 cases.

Malaria is no longer endemic in the Caribbean. The exception, however, is the island of Hispaniola, which includes the countries of the Dominican Republic and Haiti. In 2011, 72 cases originated in Haiti.

Primaquine is the only antimalarial active against the dormant parasite liver forms. Of the 435 uncomplicated cases of P vivax and P ovule, only 41% of patients received primaquine. This suboptimal prescription practice may have been the result of primaquine manufacturing issues in 2011.

The CDC urges healthcare providers to consult resources on the CDC Web site and familiarize themselves with the prevention, recognition, and treatment of malaria. Detailed recommendations for treating malaria can be found on the CDC Web site.

Antimalarial treatment should be tailored to the patient based upon many factors, including: probable geographic origin of the parasite, the Plasmodium species, and parasite density. Patients with malaria who are severely ill should be given aggressive treatment with parenteral antimalarial therapy.

Dr. Cullen and Dr. Arguin have disclosed no relevant financial relationships.

MMWR. 2013;62:1-17. Full report


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