HealthDay News — U.S. malaria cases increased dramatically in 2011, reinforcing the need for appropriate travel medicine consultations, according to the CDC.

A total of 1,925 U.S. malaria cases in 2011, representing a 14% increase in the number of cases reported in 2010 and a 48% increase since 2008, the agency stated in Morbidity and Mortality Weekly Report. The number is the highest the country has seen since 1971 (N=3,180).

“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,” CDC director Thomas Frieden, MD, said in statement.

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The CDC emphasized the importance of directing seasonal malaria prevention messages to travelers — specifically those traveling to west Africa in early spring and India in late spring. 

“Travelers should be informed of the risk for malaria and strongly encouraged to use protective measures, including chemoprophylaxis,” CDC researchers Karen A. Cullen, PhD, and Paul M. Arguin, MD, wrote in MMWR.

To better understand trends in the disease, they analyzed data from the National Malaria Surveillance System, National Notifiable Diseases Surveillance System and direct CDC consults.

The majority of 2011 malaria cases were classified as imported. “Imported malaria can reintroduce malaria into regions, including the United States, where the disease is not endemic and environmental conditions are present that can support the lifecycle of the parasite, including the presence of an appropriate Anopheles vector.”

Among all 2011 malaria cases, there was one laboratory-acquired case, one transfusion-related case, two congenital cases and one cryptic case, they found.

The following pathogens were implicated: Plasmodium falciparum (49%), P. vivax (22%), P. malariae (3%), and P. ovale (3%). The researchers were unable to identify an infecting species in 23% of cases, and an additional 1% reported infection with two species.

Among the 929 U.S. patients for whom information was available on chemophrophylaxis and travel region, just 57 (6%) reported adhering to CDC-recommended prevention regimens. A total of five U.S. patients died from the disease in 2011.

“Several patients had delayed seeking treatment after onset of symptoms, and two patients were discharged with empiric antibiotics without an appropriate workup for fever in a traveler returning from an area where malaria is endemic,” the researchers wrote.

Signs and symptoms are often nonspecific but typically include fever. Other symptoms include headache, chills, increased sweating, back pain, myalgia, diarrhea, nausea, vomiting and cough.

Malaria should be considered in the differential diagnosis of any patient with a fever, who has returned from an area where malaria is endemic, the CDC emphasized.


  1. CDC. MMWR Morb Mortal Wkly Rep. 2013 Nov 1;62(ss05):1-17.