More than 2,000 people in the U.S. return from visits abroad with malaria every year, a new report says. The report supports data from the Centers for Disease Control and Prevention (CDC) indicating that malaria is on the rise in the U.S., and should serve as a warning to travelers who visit countries where the disease is common, experts said.
“Malaria, in the world right now, is still the leading cause of death by parasitic disease,” said the study’s lead researcher, Diana Khuu, an epidemiologist at the Fielding School of Public Health at the University of California, Los Angeles. “It’s important for everyone to take preventative measures,” she said.
Over recent decades, aggressive interventions in countries with malaria-carrying mosquitoes have reduced new cases of the disease and, more important, deaths from it. Still, in 2015, 438,000 people died from the disease worldwide, according to the World Health Organization.
In the United States, endemic malaria, meaning malaria transmitted by local mosquito populations , was eliminated in the early 1950s. But reports of travelers returning to the U.S. with cases have recently been on the rise. In the 1970s, data from the CDC’s malaria surveillance system estimated the total number of confirmed cases per year to be in the low hundreds. Since then, that number has steadily climbed to between 1,500 and 2,000.
These numbers come from physicians and lab clinicians, who are required by state law to report cases of malaria they’ve diagnosed and treated.
The information compiled is useful for characterizing who may be at risk and what interventions may work best, said Dr. Paul Arguin, chief of the Domestic Response Unit in the CDC’s Malaria Branch, but it’s also limited. The surveys don’t contain hospitalization specifics nor do they gather details on the cost of treatment, he said.
Khuu and her team set out to compile these and other details to gain a sharper look at the impact of malaria in the United States.
The researchers analyzed hospital records available in a database called the Nationwide Inpatient Sample, which is the largest publicly available sources of billing records. Scientists can query the database for a wide range of medical details, including patient demographics, diagnosis, length of stay and more.
They found that between 2000 and 2014, 22,029 people — about 2,100 people per year — were hospitalized because they had signs of malaria . Of those, at least 4,823 were diagnosed with severe cases, meaning they had kidney failure, were in a coma or had acute respiratory distress. Of the 4,823 patients, 182 died.
This average number of cases per year is slightly higher than previous CDC figures, but the researchers said they could not verify each case to confirm the diagnosis, and so the actual number could be slightly higher or lower, according to the findings, published this week in the American Journal of Tropical Medicine and Hygiene.
Khuu said that the number may indicate that many travelers to countries where malaria is common are not taking antimalarial drugs, or using mosquito repellents and bed nets while overseas, as the CDC recommends.
“It’s a preventable disease,” Arguin said. “If you are going to be traveling to a country where malaria is endemic, there are definite steps you can take to prevent.”
Dr. Arguin recommended that travelers check the CDC’s website to see if the country they’re visiting has malaria, and if so, they should visit their health care provider to get a prescription for antimalarial drugs.
Other details from Khuu’s study shed light on the population of people most affected and the region of the country with high incidences. The majority live along the East Coast of the United States and in the South Atlantic states, the part of the country where malaria was last seen.
Men accounted for 60 percent of the malaria-related hospital admissions. Most of the people admitted to the hospital with malaria (about 70 percent) came in through the emergency room.
“The high proportion of hospitalizations coming from the ER indicates that malaria can cause severe disease very rapidly, and many people with malaria may be delaying their seeking of medical attention,” Khuu said.
When Khuu and her team added up the cost of treatment, they found that each hospitalization averaged about $25,800 per person.
The economic impact of malaria is one thing people may not think about before traveling to countries where the disease exists, Arguin said. But diagnosing and treating a case can be expensive, especially if there’s a prolonged hospital stay associated with it, or if a person develops a permanent disability.
“All of those can be dramatic costs associated with malaria, which ideally could have been prevented in the first place,” Arguin said.