It’s a fever, and it’s surprisingly common when people visit friends or family in distant lands. Help prevent your patients from becoming victims.

When patients say fever is their chief complaint, ask if they’ve been out of the country lately. According to a recent analysis, fever often signals a serious illness, particularly when patients have been visiting family or friends in the developing world.

Researchers from the GeoSentinel Surveillance Network analyzed the records of 24,920 patients who visited one of its clinics after an international trip. The data came from 31 facilities on six continents and covered the years 1997-2006.

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Almost 7,000 of the ailing patients (28%) listed fever as a primary reason for their visit to the clinic. A quarter of this group (26%) required hospitalization, compared with 3% of those who had no fever.

“Although travelers may have infections that are caused by common, globally distributed pathogens [e.g., HIV, cytomegalovirus, and Toxoplasma gondii], they may acquire infections that are unfamiliar to most clinicians,” the researchers warn. “All clinicians must make a travel history part of the initial evaluation.”

Of the patients with fever, 35% had a systemic illness, 15% had a diarrheal disease, and 14% had a respiratory illness. More patients had malaria than any other specific infection (21%), followed by dengue, enteric (typhoid) fever, and rickettsioses. However, a fifth of patients (22%) were not diagnosed with a specific illness.

Which diseases occur where

Diagnoses varied by region visited and length of time since the patient’s return. People who had visited sub-Saharan Africa, south-central Asia, or Latin America were most likely to suffer fever. Those who returned from Oceania or sub-Saharan Africa were most likely to have malaria. Dengue was the primary diagnosis among people who had been to Southeast Asia but was rarely seen in those who had visited Africa. At least 70% of the typhoid cases resulted from exposures in southern Asia.

Most travel-related infections have incubation periods shorter than 30 days, the study notes, and that affected the febrile causes. For example, two thirds of patients with dengue or falciparum malaria—the most life-threatening form of that disease—sought attention for fever within a week or two of their trips. However, the researchers point out, many infections can lie dormant for more than 30 days. These include hepatitis, vivax malaria, and TB, among others, which were found in patients after four to six weeks or longer.

The study found that individuals who traveled to visit friends or relatives were more likely to fall ill with fever than people who traveled for other reasons, such as tourism or business. Most were immigrants who were visiting their native towns.

“They are more likely to travel to rural and more remote areas to visit family and relatives,” says Mary E. Wilson, MD, the study’s lead investigator. “They often live with local residents and may not have access to clean water, screens, etc., that the typical tourist would have in a hotel.”

Overall, 17% of the sick travelers had illnesses, such as influenza and malaria, that could have been prevented by vaccines or chemoprophylaxis. Those visiting friends and relatives were more likely than other travelers to have a vaccine-preventable cause of fever, presumably because they were less likely to have had a checkup before their trips. The most common vaccine-preventable infections were typhoid fever, acute hepatitis A, and influenza A (Clin Infect Dis. 2007;44:1560-1568).

False sense of invincibility

Most immigrants don’t get vaccines or antimalaria pills because they can’t afford them, says David O. Freedman, professor of epidemiology at the Center for Geographic Medicine of the University of Alabama in Birmingham, who contributed to the study as part of the GeoSentinel Surveillance Network.

“They scrape together enough money to take their family to visit, and that may cost thousands of dollars,” he says. “They don’t have the money for pills or vaccines.” Although they do get their children vaccinated, they frequently skip getting the shots themselves.

That’s because immigrants tend to have a false sense of invincibility. “There is a belief that ‘I grew up there, so I am immune,’ ” Dr. Freedman says, “and that’s just not true. Any level of immunity they may have had is completely lost within a few months.”

Dr. Wilson says that overconfidence also leads to ignoring other precautions. “Visitors frequently do not perceive an increased risk because they are going home, so they may not use repellents, bed nets, etc.,” she says.Because people traveling to visit friends and relatives tend not to schedule pre-travel checkups, Dr. Wilson suggests clinicians take a proactive approach. “Make inquiries about planned or possible travel a routine part of every encounter,” she urges, “both for routine checkups and for any illness. Many patients are simply unaware that special risks are present in other regions.”

Ms. Dembrow is a senior editor with The Clinical Advisor.

Dr. Wilson is associate clinical professor of medicine at Harvard Medical School and associate professor of population and international health at the Harvard School of Public Health.