Incidents of serious and fatal malaria are more common in the United States than previously reported, according to a study published Monday in the American Journal of Tropical Medicine and Hygiene. According to the study, the total cost of treating malaria patients in the United States from 2000 to 2014 was about $555 million.
For the study, researchers looked at approximately 100,000 million hospital discharge records spanning 2000 to 2014 from HHS' Agency for Healthcare Research and Quality's National Inpatient Sample.
The researchers identified 22,029 patients who were hospitalized for malaria in the United States between 2000 and 2014—about 2,100 cases per year. Close to 5,000 of those patients experienced serious complications associated with the infection, such as coma or kidney failure, and 182 of the patients died.
The researchers' estimates were higher than those previously reported by CDC. According to the New York Times, CDC has reported that between 1,500 and 2,000 cases of malaria occur in the United States annually. Researchers added that the actual number of malaria cases that occur among individuals in the United States could be higher because some patients might not be hospitalized for the disease.
Diana Khuu, the study's lead author and an epidemiologist at the University of California-Los Angeles' Fielding School of Public Health, said the cause of the discrepancy might be that CDC's estimates are based on physician and laboratory reports and many physicians do not know they are obligated to report malaria cases to state health officials.
According to the researchers, most incidences of malaria reported in the United States occurred among immigrants who visited their home countries and did not take precautions to guard themselves against the disease. "We don't know of any active transmission in the [United States] so we assume that these cases are all travelers or immigrants," Khuu said.
The researchers hypothesized that many of such individuals had experienced repeated malaria infections when they were younger and thus expected that they had developed immunity to the disease. However, that immunity had depleted after the individuals spent years in the United States.
William Moss, a pediatrician and professor at the Johns Hopkins Bloomberg School of Public Health, said, "Individuals may think that they have some protection because they had malaria infections during childhood. And then they go back, they don't take the proper chemoprophylaxis (anti-malarial pills), and they're susceptible not only to infection but to the disease."
Khuu said malaria cases reported in the United States typically occurred among men ages 20 to 50 who are from Africa or the Caribbean. The researchers wrote, "Malaria-related hospitalizations occurred disproportionately among patients who were male, black, or 25 to 44 years of age."
The researchers also found that 14 percent of women who were hospitalized for malaria in the United States were pregnant. The researchers noted that pregnancy can lower a woman's immune defenses. According to the Times, malaria can be fatal to pregnant women and fetuses.
According to the researchers, malaria patients often were hospitalized for multiple days, spending an average of 4.36 days in the hospital. The hospitalizations cost an average of $25,789.
The researchers concluded that "the number of imported malaria cases has steadily increased in the United States," adding that malaria "imposes a substantial disease burden in the" country. As such, the researchers wrote that "enhanced primary and secondary prevention measures, including strategies to increase the use of pre-travel consultations and prompt diagnosis and treatment are needed."
Khuu said, "We do have a good anti-malaria medicine that travelers can take but apparently some people are just not using it."
3 African countries to test first malaria vaccine
In related news, the World Health Organization (WHO) on Monday announced that researchers next year will test the first-ever malaria vaccine in three African countries, the Associated Press reports.
About 200 million people are infected with malaria annually, and about 500,000—most of whom are children in Africa—die from the disease each year.
According to WHO, the researchers will test the vaccine among thousands of children ages five months to 17 months in Ghana, Kenya, and Malawi. At least 120,000 children in each country will receive the vaccine, which must be administered in four separate doses over an 18-month period.
Matshidiso Moeti, WHO's regional director for Africa, said the vaccine—which has been found to be partially effective—could save tens of thousands of lives if used in tandem with existing measures to combat malaria. He added, "Information gathered in the pilot program will help us to make decisions on wide use of this vaccine" (McNeil, New York Times, 4/24; Khuu et al., American Journal of Tropical Medicine and Hygiene, 4/24; Mohney, ABC News, 4/24; Beaubien, "Goats and Soda," NPR, 4/24; Lagassee, Healthcare Finance News, 4/24; AP/STAT News, 4/24; Gallagher, BBC News, 4/24).
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