Foreign travel to exotic places is no longer the province of the rich or reckless. An increasing number of tourists are setting off on African safaris, fishing trips to the Amazon and treks through Nepal, according to the World Tourism Organization. While most will bring back nothing more exotic than souvenirs and photos, a small percentage will acquire illnesses requiring medical care.
Up to 64% of travelers abroad have some sort of health problem during or shortly after a trip—especially those who go to developing countries—but most escape with a fairly mild bout of diarrhea, a cold or a skin irritation, research has shown. Still, an unlucky 8% of people who travel to developing regions acquire an illness or condition that leads them to seek medical care, and about 11% of those require inpatient care, according to a 2006 New England Journal of Medicine (NEJM) study of 17,353 ill patients at 30 travel clinics worldwide.
The World Tourism Organization's latest estimates show that 806 million people traveled abroad in 2005, a 5.5% increase over the previous year—and travel to Africa had the biggest gain. Chances are fairly good, then, that the average hospitalist will encounter patients with travel-acquired illnesses at some point in her career. The question is: How will she recognize them?
Hospitalists need to know which symptoms and diseases they are most likely to see. Fever is the most common symptom for which a returning traveler is admitted to the hospital, according to Lisa Winston, MD, assistant professor in the division of infectious diseases at the University of California, San Francisco.
Malaria used to be the main culprit of febrile disease in returning travelers, but it has gotten some competition in recent years, she added.
“Malaria and dengue fever kind of compete for number one and two. Typhoid is usually near the top of the list, and rickettsial diseases are common or emerging as well, especially from Africa,” Dr. Winston said. “Leptospirosis is good to know about; it usually involves exposure to fresh water and is found all over the world. The highest U.S. incidence is in Hawaii.”
Visitors to sub-Saharan Africa, Southeast Asia or South-Central Asia are the most likely to need inpatient care compared with those who visited other regions, the NEJM study found. Febrile patients who went to sub-Saharan Africa are most likely to have malaria, while dengue fever is the likely culprit for recent visitors to Southeast Asia and the Caribbean. Typhoid fever, meanwhile, may strike recent travelers to Central Asia.
Rickettsial infections—especially tickborne spotted fever—appear almost exclusively in travelers to sub-Saharan Africa, the study found.
Beyond this, exotic illnesses are quite rare. Among the more than 17,000 ill patients studied, none had yellow fever, Ebola, Japanese encephalitis or rabies, for example. Only one had cholera and one had meningococcal meningitis, according to the study.
Asking is half the battle
Routinely asking about a patient's travel history is the single most important strategy for detecting travel-acquired illness, experts agreed. A patient won't necessarily offer this information on her own, especially if she took a trip a few months ago or travels frequently.
“You hear anecdotes about patients, particularly in the South Central U.S., who take long weekend fishing trips to the Amazon and they get ill with yellow fever two or three weeks after they get back,” said Brent Burkey, MD, a hospitalist who specializes in travel medicine at the Cleveland Clinic. “They go to the doctor, who doesn't ask about travel and thinks it is just a virus or the flu, and ultimately the disease gets the best of the patient.”
After finding out where a patient traveled, the physician should ask what sort of immunizations or medications the patient received or took before her trip, if any. Other questions include whether the patient went hiking, ate raw meat or seafood, swam in fresh water, got insect or animal bites, spent most of her time in cities or rural areas, had any sexual encounters, used needles, or got tattoos, Dr. Winston said.
“You should focus on exactly where and when the patient traveled, and what he or she did while there,” Dr. Winston said. “A business traveler who stayed in air-conditioned hotels will have different risks than someone who backpacked in rural areas.”
A physician may have to make a patient—and himself—a bit uncomfortable to get all the relevant exposure histories. If he discovers a patient traveled to an area with a high prevalence of AIDS or hepatitis B, for example, he must ask questions that target such exposures, said Aaron Kosmin, MD, a travel medicine specialist at Albert Einstein Medical Center in Philadelphia.
“If a man went to Thailand on business and returns with fever, lymphadenopathy and a headache, you should ask if he had contact with a sex worker,” Dr. Kosmin said. “People do things on vacation they wouldn't necessarily do at home, and they might not tell you about them unless you ask.”
Travelers who visit family and friends abroad are more at risk for travel-related infections, he added. They are less likely to seek pre-travel advice and immunization, are more likely to be exposed to persons and locations outside the safer tourist destinations, and tend to underestimate their risks, Dr. Kosmin said.
Timing is everything
Sixty-four percent of those patients who sought medical attention after traveling to developing countries did so within a month of their trip, the NEJM study found. Yet 10% weren't seen until more than six months after the trip, because their disease developed slowly or had a longer incubation period.
Pairing a patient's travel dates with a general knowledge of the incubation period for the most common travel illnesses is key to making a differential diagnosis, said Dr. Kosmin (see Table 2).
“If someone who traveled six months ago to Africa presents with shock, fever and spontaneous hemorrhage, you know they don't have Ebola. But knowing malaria can have a prolonged incubation period and cause sepsis with DIC [disseminated intravascular anticoagulation] can prompt you to do more pertinent testing,” Dr. Kosmin said.
Patients with falciparum malaria (the most common and severe of the four malaria types), dengue fever and typhoid usually develop symptoms within two to three weeks, while other types of malaria can present months or even years later, Dr. Winston said.
“Fever beginning three weeks or longer after return greatly reduces the probability of dengue fever, rickettsial infections and viral hemorrhagic fevers in the differential diagnosis,” according to the CDC's “Health Information for International Travel 2008”—otherwise known as the Yellow Book.
Two-thirds of dengue fever patients present within a week of returning from a foreign country, said Dr. Burkey, while two-thirds of those with falciparum malaria present within two weeks. On the other hand, only 25% to 30% of patients with vivax malaria are seen within two weeks, and half are seen more than six weeks after they return home, he said.
“There were cases of Vietnam soldiers who presented with malaria years after they left Asia,” Dr. Burkey said.
Calling in experts
Because malaria can present with a fever and respiratory symptoms, it can easily be mistaken for the flu or pneumonia. Dengue fever, meanwhile, is sometimes mistaken for meningitis, Dr. Kosmin said.
That's why, if a hospitalist has any suspicion that a condition might be related to a tropical illness, it is important to consult an infectious disease expert right away, Dr. Burkey said. Conditions can get much worse if they are misdiagnosed and allowed to progress without treatment.
“I know of a case where a traveler returning from Africa developed some poxlike lesions on his shins and ankles and was misdiagnosed, and he eventually required hospitalization because it got worse. As soon as the infectious disease doctor was called in and took the travel history, African tick-bite fever was diagnosed,” Dr. Burkey said.
To find a provider who practices clinical tropical medicine, hospitalists can get a state-by-state listing from the American Society of Tropical Medicine and Hygiene or the International Society of Travel Medicine.
The common diagnoses
Malaria. Between 1995 and 2004, there were 7,944 cases of malaria in the U.S. reported to the CDC, 43 of which were fatal. Of those 43, all but five were due to falciparum malaria.
A diagnosis of malaria should be “routinely considered” for anyone who has traveled to a malarious area in the several months before symptom onset, the CDC Yellow Book says. Symptoms of malaria are usually nonspecific and most commonly consist of fever, malaise, weakness, gastrointestinal complaints, neurologic complaints (dizziness, confusion, disorientation), headache, back pain, myalgia, chills and/or cough, the book says.
“With falciparum malaria in particular, you can be a little sick and then progress to become critically ill in a matter of hours,” Dr. Kosmin said. “This is why the CDC recommends that any patient with fever for whom malaria is in the differential diagnosis should undergo an urgent medical evaluation.”
Laboratory diagnosis of malaria, via microscopic examination of thick and thin blood smears, should almost always be confirmed before treatment is given. The only exceptions are under extreme circumstances, like severe disease, a strong clinical suspicion of malaria, or if lab results can't be obtained promptly, the Yellow Book says; testing should also be repeated if the initial result is negative.
Dengue fever. After incubating 3 to 14 days, dengue has a sudden onset of high fever, severe headache, and joint and muscle pain, which are easily mistaken for influenza. Many patients have nausea, vomiting and a maculopapular rash, which appears three to five days after the fever starts and can spread from the torso to the limbs and face. Acetaminophen is usually recommended for managing the fever, but aspirin and nonsteroidal anti-inflammatory drugs shouldn't be used because of their anticoagulant properties. Rest and fluid intake should be encouraged, the Yellow Book says.
Typhoid fever. A persistent high fever (103° F to 104° F) is the strongest indicator of typhoid, with other symptoms including headache, malaise, splenomegaly, bradycardia and a rash of flat, rose-colored spots. Treatment involves specific antimicrobial therapy, which should be determined by data on sensitivity, especially for travelers to South Asia. Patients should be monitored to ensure that their fever wanes within a few days of starting treatment; if not, alternative antimicrobial agents should be considered, the Yellow Book says.
Rickettsial infections. There are many types of rickettsial infections—the Yellow Book lists more than 30. Because they present with vague symptoms (fever, headache and malaise), they are often mistaken for other illnesses. Lab tests are needed to help identify which type of infection a patient has. Figuring out where and how the patient got exposed to the disease is especially helpful in narrowing down the type. Most rickettsial illnesses are treated with antibiotics.
Leptospirosis. With its usual symptoms of fever, chills, gastrointestinal upset and myalgia, leptospirosis mimics malaria, dengue and typhus. Confirming the diagnosis requires laboratory testing. Leptospirosis is treated with antimicrobial agents.
For more on travel medicine, see “Test Yourself.”
The dangers of dengue
Dengue fever may become prevalent in the U.S. if the disease continues to increase in severity and expand into temperate climates, according to Anthony S. Fauci, MACP, director of the National Institute of Allergy and Infectious Diseases.
Formerly found in tropical and subtropical climates, dengue is becoming a more serious problem along the U.S.-Mexico border and in the commonwealth of Puerto Rico, according to an article written by Dr. Fauci and his senior scientific advisor, David M. Morens, MD. The article was published in the Jan. 9 and Jan. 16 double issue of the Journal of the American Medical Association.
While there is minimal dengue-related illness in the U.S. currently, the disease tends to take hold in dramatic epidemics, and efforts to control mosquitoes that transmit dengue have fallen short of their goal, said Drs. Fauci and Morens. The mosquitoes have been found in 36 U.S. states since 1985.
In other parts of the world, the disease often follows the mosquitoes, the doctors said. They called for more research into the illness, for which there are no specific vaccines or treatments.
“Widespread appearance of dengue in the continental United States is a real possibility,” the doctors wrote in their JAMA article.