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Issue: September 2017
September 18, 2017
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Many international travelers ignore dangers of infectious disease

Issue: September 2017
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Studies have shown that many Americans do not take important precautions before traveling to countries in which certain infectious diseases are endemic, and the consequences can be serious.

Travelers face threats ranging from mosquito-borne diseases like malaria and Zika virus to those lurking in food and drinking water, such as the bacteria that cause traveler’s diarrhea. Experts like David R. Hill, MD, a professor of medical sciences and director of global public health at the Frank H. Netter, MD, School of Medicine at Quinnipiac University, have expressed concern over Americans’ lack of knowledge about these threats.

“Several studies have confirmed that many travelers — sometimes more than half — do not seek adequate pretravel advice,” said Hill, who is also an executive committee member of the American Society of Tropical Medicine and Hygiene. “Thus, they go without proper knowledge about disease avoidance, vaccines and self-treatment options. Although this does not translate to adverse outcomes for many, others will be left unprepared in the event of a diarrheal illness, complication of a pre-existing condition or an accident or injury. These events can prematurely end a holiday or business trip, lead to high medical expenses and, for those who do not take out travel medicine insurance, result in huge costs for medical repatriation.”

Photo credit: CDC

Joanna Gaines, PhD, MPH, a senior epidemiologist with the CDC’s Traveler’s Health Branch, Division of Global Migration and Quarantine, said the exact number of medical tourists from the United States is unknown, but that some studies suggest hundreds of thousands of U.S. residents seek care abroad each year.

Infectious Disease News spoke with several travel medicine experts about how clinicians can help travelers avoid contracting — and perhaps further transmitting at home — potentially dangerous pathogens.

Dangers that await

The endemic diseases encountered overseas vary by region and traveler behavior. Traveler’s diarrhea is a disease seen in many developing countries.

“Traveler’s diarrhea is a risk in most low-income settings where food and water hygiene may be compromised,” Hill said.

David R. Hill

The growing threat of drug resistance can add to the problem, he said.

“Recent data indicate that travelers who have been treated with antibiotics for traveler’s diarrhea can carry or develop resistant bacteria in their stools,” Hill said. “Thus, antibiotics should be used sparingly.”

For example, a study published in Clinical Infectious Diseases in 2015 showed that among 430 Finns who traveled outside Scandinavia, 90 (21%) had become colonized by extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae while traveling. Of those who developed diarrhea and treated it with antibiotics, 37% were colonized by ESBL-producing Enterobacteriaceae (adjusted OR = 3; 95% CI, 1.4-6.7).

The risk for colonization was greatest among those who traveled to South Asia, 46% of whom were colonized. Among travelers in each of three other regions — Southeast Asia, East Asia and North Africa/the Middle East — 33% were colonized.

In a separate study that focused on the same Finnish cohort, researchers found that loperamide was a safe alternative to antibiotics for treating traveler’s diarrhea. They assessed the treatment choices of 288 participants who reported having diarrhea while traveling abroad. ESBL-producing Enterobacteriaceae colonized 21% of those who took no medication for their diarrhea, 20% of those who took only loperamide, 40% of those who took only antibiotics and 71% of those who took both loperamide and antibiotics.

Stephen J. Gluckman, MD, a professor of medicine at the Hospital of the University of Pennsylvania and medical director of Penn Global Medicine, said tropical mosquito-borne diseases represent the largest threat to travelers.

“If you define it in terms of numbers and mortality, malaria is overwhelmingly the biggest threat,” Gluckman told Infectious Disease News.

A study published in the American Journal of Tropical Medicine and Hygiene in April showed that U.S. hospitalizations for malaria were more common than previously thought.

Assessing hospitalizations between 2000 and 2014, the researchers estimated that about 2,100 people in the U.S. may be infected with malaria each year on average. This exceeds the CDC’s high-end estimate of 1,500 to 2,000 yearly cases in the U.S. In addition, of the estimated 22,029 malaria hospitalizations during the study period, 4,823 (22%) were severe cases, and 182 patients died in hospital.

The study did not include data showing how many cases were travel-related, but researchers said the higher-than-expected prevalence could be due to increased travel to malaria-endemic regions and a lack of safety preparations. They also suggested immigrants who visit their country of origin could be returning to the U.S. with the disease.

Phyllis E. Kozarsky, MD, a professor of medicine at the Emory University School of Medicine’s division of infectious diseases and one of the founders of the International Society of Travel Medicine, said immigrants visiting friends and relatives are at especially high risk for infection.

“These travelers represent a large proportion of U.S. travelers now and are at greater risk of acquisition of some illnesses due to a number of factors: lack of awareness of risk, financial barriers to pretravel health care, culture and language barriers, barriers to trust, last-minute travel plans and divergent health beliefs,” she said. “One initiative, called Heading Home Healthy, aims to improve the pretravel health care of these groups.”

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Hill said that malaria, which is endemic in tropical regions, is not exempt from resistance to treatment.

“Most severe Plasmodium falciparum malaria throughout the tropics, particularly in sub-Saharan Africa, is resistant to older antimalarials,” Hill said. “So, it is important to take the correct drug ... and make sure the traveler is adhering to it. Most cases of imported malaria in the U.S. occur in persons who took no antimalarial, took the incorrect drug or did not complete the prescribed course.”

Another disease of concern, and one of the most recent to affect the U.S., is Zika virus. With its potential to cause microcephaly and other serious congenital defects, Zika has become a significant concern for travel medicine experts and other health care providers.

As of mid-August, the CDC listed 97 countries that it advises pregnant women not to visit because of the risk for Zika infection. They include Mexico, 30 countries in Africa, 14 in Asia, 26 in the Caribbean — including Puerto Rico and the U.S. Virgin Islands — seven in Central America, eight among the Pacific Islands and 11 in South America.

Between Jan. 1 and Aug. 16, 203 symptomatic Zika virus cases were reported in U.S. states, according to the CDC. All but two cases were documented in travelers who had returned from Zika-affected areas.

Taking precautions

Among the precautions travel medicine experts often stress are vaccines. Yet data suggest that there is much ground to be made up in improving vaccination rates among those traveling overseas.

In one study published in the Annals of Internal Medicine, researchers found that less than half of people who were eligible for the measles, mumps and rubella (MMR) vaccine did so before traveling abroad. Among 6,612 adults aged 60 years or younger who received pretravel consultations at 24 U.S. clinics, 48% refused the vaccine. The health care provider decided against vaccination in 28% of cases, and health system barriers prevented vaccination in 24%.

In July, the CDC reminded those traveling to Europe to take measures to protect themselves against measles following severe outbreaks of the disease on the continent.

Since January 2016, more than 14,000 cases of measles have been reported in Europe, according to the European Centre for Disease Prevention and Control (ECDC). As of Aug. 25, 40 people in Europe had died from the disease in that period, the ECDC reported.

In 2017, measles cases have been reported in 15 European countries, according to the ECDC. The CDC issued travel health notices for five countries in which there had been measles outbreaks since November 2016 — Belgium, France, Germany, Italy and Romania.

Kozarsky pointed to the outbreaks as one example of why travel medicine providers double check on a patients vaccination history.

“This is one reason why travel health advisors review routine vaccinations with their patients, to make sure they are protected against illnesses such as measles, mumps, rubella, influenza, diphtheria, pertussis, etc.,” she said.

Gluckman said vaccine choice can be determined by destinations more specific than countries.

Stephen J. Gluckman

“It’s not just by country but by regions within a country,” he said. “For instance, if one is going to Peru but is only going to be on the Inca Trail, there’s no risk of yellow fever. It’s too high for mosquitos to fly. But if they’re going to Peru and they’re going down to the Amazon, then there is a risk for yellow fever ... You have to know quite precisely where in a country somebody is going to give them the best advice.”

Gluckman added that measles, tetanus and pertussis vaccines should be considered because those diseases can be risks in developing countries. Malaria prophylaxis medications are also recommended.

“If [travelers] are going to an area where there is potential to get malaria, the medical answer is they must take something to prevent it,” Gluckman said. “Malaria is a potentially fatal disease.”

Medical tourism

Whereas many Americans traveling overseas ignore inherent disease risks, some even add to the danger of infection by having surgery or other treatments performed in countries in which the chances of infection are greatly increased. The practice is commonly known as medical tourism.

Knowing why a patient seeks care abroad can help guide the discussion. Leigh Turner, PhD, an associate professor at the University of Minnesota School of Public Health’s Center for Bioethics, said the reasons vary widely.

“There’s a litany of reasons,” said Turner, who rejects the term “medical tourism,” saying it implies a casual or leisurely motive rather than a desire to undergo a serious and possibly dangerous procedure, and prefers “medical travel” or “health-related travel.”

According to the CDC, common procedures that Americans seek overseas include cosmetic, orthopedic and cardiac surgery, as well as cancer treatment and dental procedures, among others.

One of the most significant obstacles to receiving care in the U.S. can be cost, Turner said.

“An important driver in the U.S. is just differences in cost of care,” he explained. “In general, I think it’s fair to say that in the U.S., prices are extremely high relative to costs of procedures in other countries.”

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A lack of insurance coverage can be an added obstacle.

“Individuals who lack health insurance or are underinsured may find themselves in circumstances in which going out of country is a draw, and it’s mostly because they’re trying to avoid medical debt and medical bankruptcy,” Turner said.

Some patients mistakenly believe the procedure they need is not available in the U.S.

“If someone wants to have a stem cell procedure for ALS or MS, there is this assumption that you have to go to Mexico or India,” Turner said. “The reality is there’s a substantial amount of travel within the U.S. ... You can go to any one of hundreds of facilities in the U.S.”

Medical tourism destinations vary widely and span the continents, according to Davidson H. Hamer, MD, principal investigator for the International Society of Travel Medicine’s GeoSentinel, a network of travel clinics that conduct surveillance of travel-related morbidity. Hamer is also a professor of global health and medicine at Boston University.

“There are multiple countries in South America and the Caribbean, such as Argentina, Brazil and the Dominican Republic, South Asia, Southeast Asia and South Africa, that are commonly visited,” he told Infectious Disease News.

Hamer said lower safety standards in poorer countries increase the chances of infection.

“There is a substantial risk of wound infection, as well as wound breakdown and persistent pain, for medical tourists because the quality of infection prevention measures in many low- to middle-income countries is inadequate,” he said. “Besides the risk for wound infections, medical tourists are likely to be exposed to hospital environments where they may become colonized with multidrug-resistant bacteria. They can then carry these organisms home and potentially spread them to family members.”

Hamer said medical tourists are at risk for acquiring a range of different pathogens, from common bacterial causes of wound infection to mycobacteria.

“The more routine bacterial causes, such as Staphylococcus aureus and gram-negative bacilli, are likely to be multidrug resistant,” he added.

In July 2017, the CDC issued a warning stating that several U.S. residents had been infected with nontuberculosis mycobacteria after undergoing cosmetic surgery in the Dominican Republic. Most had undergone procedures at a clinic in Santo Domingo, the agency announced.

Eight U.S. city and state health departments reported the cases, a CDC spokesperson told Infectious Disease News at the time.

In 2014, five New York State residents tested positive for Coxiella burnetii, which causes Q fever, after traveling to Germany to receive live cell therapy, researchers reported in MMWR. The treatment, also known as “fresh cell therapy,” involves the injection of processed cells from animals to treat various ailments.

The New Yorkers had been among a group that traveled to Germany’s Rhineland-Palatinate state to receive injections of sheep cells. They tested seropositive for Q fever after showing symptoms of the disease, as did a sixth person from Canada who had also received the procedure.

Travel medicine providers acknowledge the need to steer patients away from medical tourism.

“The challenge, though, is that most patients will not admit to their primary care providers or specialists that they are planning to be medical tourists,” Hamer said. “ID specialists need to be aware of the risks associated with medical tourism, including the potential for atypical mycobacteria to be responsible for wound infections. This means taking a detailed travel history, doing appropriate wound cultures and [annotating] proper contact precautions for infected patients.”

The exact number of medical tourists from the U.S. is unknown.

“There is no nationwide surveillance system for medical tourism, and any estimates must be interpreted with caution,” Joanna Gaines, PhD, MPH, a senior epidemiologist with the CDC’s Traveler’s Health Branch, Division of Global Migration and Quarantine, told Infectious Disease News. “Some studies estimate that hundreds of thousands of U.S. residents travel internationally for care each year, both to developing and developed countries.”

Uncertainty about the number of medical tourists makes it difficult to assess the risk for infection, Gaines explained.

“Additionally, a patient who returns with an infection may not disclose his travel history or that he received medical care abroad,” she said. “Several different disease outbreaks among U.S. residents have been documented in the scientific literature, particularly skin and soft tissue infections most likely acquired during surgery.”

She said clinicians can consult the CDC’s Yellow Book for guidance in treating patients who are considering medical tourism.

The pretravel visit

Preparations for travel abroad should include visiting a travel medicine clinician who, in turn, should educate the patient on what precautions to take and where to check for useful information, according to experts.

“In general, in the U.S., there is little awareness of illnesses that plague many parts of the world,” Kozarsky said. “There is little information about many of these illnesses ... found in the usual educational venues, or even in news media, except if there is a major outbreak of a presumed ‘scary’ disease like Ebola.”

The advice that Americans typically receive, Kozarsky said, tends to come from friends, travel agencies, consulates and other sources. But it may not be accurate or sufficient.

“Primary [health care] providers also often are not equipped with up-to-date information about health problems in other countries,” she added.

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According to Hill, clinicians should think about the risks of each particular trip and the patient’s current health status.

Davidson H. Hamer

“The pretravel visit is a time to assess the underlying health of the traveler,” he said. “Do they have pre-existing conditions that could be exacerbated during travel, such as diabetes, chronic lung or cardiac disease?”

Patients should also consult the CDC webpage at www.cdc.gov/travel for advice and information on disease prevalence in certain countries, Hill advised.

Clinicians can tell travelers what foods and drinks to avoid, depending on their destination, and what types of medicines they should bring with them.

“They can carry self-treatment for traveler’s diarrhea — hydration with potable fluids, Pepto-Bismol for symptoms of nausea and mild diarrhea, loperamide to treat symptoms of frequent nonfebrile, nonbloody diarrhea when they are in a situation where diarrhea interferes with important activities, and a self-treatment course of antibiotics for severe or moderate diarrhea,” Hill said.

He also discussed pointers clinicians can give patients concerning insects, especially mosquitos that could transmit malaria.

“Malaria is transmitted by dusk-to-dawn-biting Anopheles mosquitos, so using barrier clothing — loose-fitting, light weight and impregnated with permethrin — is advisable,” he explained.

The absence of treatment options for certain diseases makes it important for travelers to avoid transmission in the first place, Gluckman said.

“They need to think about not getting bitten by mosquitos and ticks,” Gluckman stressed. “We have pills to prevent malaria, but we don’t have pills to prevent dengue, chikungunya and Zika, or a lot of tick-borne diseases. So that basically means they need to have a discussion about insect repellants and insecticides, and about screens and the safer and less safe times of day to be out.”

The 2018 edition of the CDC’s Yellow Book includes updates on emerging diseases, including Zika, Ebola and MERS.

Given the available resources, the challenge that remains is reaching travelers who either do not know they exist or simply disregard them.

Hill suggested linking travel agency services to health websites. He also said travel medicine experts and officials should “inform primary care physicians and internists of the importance of providing competent pretravel care using available resources to tailor the pretravel preventive measures.”

Hill also urged the use of public health campaigns, which were done effectively to raise awareness of Zika virus. These campaigns can inform travelers of risks and prophylactic options. Prevention, Hill stressed, is perhaps the most valuable tool clinicians can provide.

“They should provide enough information so that if an illness occurs, the traveler has the confidence to self-manage or the knowledge of how to seek medical care,” he said. “But as always, prevention, avoiding illness, is best.” – by Joe Green

  • For more information:
  • Joanna Gaines, PhD, MPH, can be reached at the CDC, 1600 Clifton Rd., Atlanta, GA 30329; email: jgaines@cdc.gov.
  • Stephen J. Gluckman, MD, can be reached at the University of Pennsylvania, 3400 Civic Center Blvd., Philadelphia, PA 19104; email: Stephen.Gluckman@uphs.upenn.edu.
  • Davidson H. Hamer, MD, can be reached at Boston University, One Silber Way, Boston, MA 02215; email: dhamer@bu.edu.
  • David R. Hill, MD, can be reached at Quinnipiac University, 275 Mount Carmel Ave., Hamden, CT 06518; email: David.Hill@quinnipiac.edu.
  • Phyllis E. Kozarsky, MD, can be reached at Emory University, 550 Peachtree Rd., Suite 7000, Atlanta, GA 30308; email: pkozars@emory.edu.
  • Leigh Turner, PhD, can be reached at the University of Minnesota, 100 Church St. SE, Minneapolis, MN 55455; email: turne462@umn.edu.

Disclosures: Gaines, Gluckman, Hamer, Hill, Kozarsky and Turner report no relevant financial disclosures.

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