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Traveling patients, traveling disease: Ebola is just the tip of the iceberg

Many in the media and academia (myself included) have been discussing the Ebola crisis, and more specifically, the issues that arise as Ebola has traveled with infected patients and health care workers to the United States and infected other US citizens.

These discussions have been fascinating and frightening, but the terrifying truth is that Ebola is just the tip of the iceberg. Diseases have long traveled with patients, and as the phenomena of medical tourism and the more general globalization of health care grow, these problems are likely to grow as well.

Medical tourists are very good targets of opportunities for pathogens. Many are traveling with compromised or suppressed immune systems to destination countries for treatment with relatively high infection rates, including the risk of exposure to multi-drug–resistant pathogens.

Doctors typically distinguish commensals—the bugs we normally carry on our skin, mouth, digestive tracts, etc.—from pathogens, the harmful bacteria that cause disease through infection. But what is commensal for a person in India might be an exotic pathogen for a US population. Medical tourist patients are transporting their commensals and pathogens to the hospital environments of the destination countries to which they travel, and are exposed to the commensals and pathogens of hospitals and population at large in the destination country. These transmissions tax the health care system and the knowledge of physicians in the home country to whom the new microbe may be unknown, and diagnosis and treatment more difficult.

Air travel can involve each of the four classical modes of disease transmission: contact (e.g. body-to-body or touching an armrest), common vehicle (e.g. via food or water), vector (e.g. via insects or vermin), and airborne (although more recent planes are equipped with high efficiency particulate air (HEPA) filters reducing transmission risk, older planes are not).

We have seen several diseases travel in this way. The Severe Acute Respiratory Syndrome (SARS) outbreak of 2003 involved a three-hour flight from Hong Kong to Beijing carrying one SARS-infected passenger leading to sixteen passengers being subsequently confirmed as cases of SARS, with eight of those passengers sitting in the three rows in front of the passenger.

In January 2008, a new type of enzyme was detected in bacteria found in a fifty-nine-year-old man with a urinary tract infection being treated in Sweden. The man, Swedish but of Indian origin, had in the previous month undergone surgeries at two hospitals in India. The enzyme, labeled “New Delhi metallo-beta-lactamase-1 (NDM-1)” was able to disarm a lot of antibiotics, including one that was the last line of defenses against common respiratory and urinary tract infection.

In 2009, a study found that twenty-nine UK patients had tested positive for the bacteria-carrying NDM-1 and that seventeen of the twenty-nine (60%) had traveled to India or Pakistan in the year before. A majority of those seventeen received medical treatment while abroad in those countries, some for accidents or illness while traveling and others for medical tourism, either for kidney and bone marrow transplants or for cosmetic surgery.

High-income countries face significant problems with these infections. A 2002 study estimated that 1.7 million patients (ninety-nine thousand of whom died as a result) developed health care-acquired infections in the United States that year. In Europe these infections have been estimated to cause thirty-seven thousand deaths a year and add US $9.4 billion in direct costs

What can be done? Although in theory airline or national travel rules can prevent infected patients from boarding planes, detecting these infections in passengers is very difficult for the airline or immigration officials, and concerns about privacy of patients may chill some interventions. A 2007 case of a man who flew from the United States to Europe with extensively resistant tuberculosis and who ultimately circumvented authorities who tried to stop him on return by flying to Montreal, Canada and renting a car, shows some of the limits on these restrictions.

Part of the solution is technological. The HEPA filters discussed above on newer model planes reduce the risk substantially, and we can hope for more breakthroughs.

Part of the solution is better regulating the use of antibiotics: overuse of antibiotics when not effective or necessary, underuse of antibiotics when they are needed, failure to complete a full course of antibiotics, counterfeit drugs, and excessive antibiotic use in food animals. This is not a magic bullet, however, and we see problems even in countries with prescription systems such as the United States.

We also need much better transparency and reaction time. Some countries reacted quickly to the report of the NDM-1 cases discussed above in issuing travel warnings and informing home country physicians, while others did not.

Finally, as became evident with Ebola, we need better protocols in place to screen returning medical tourism patients and to engage in infection control when needed.

Headline image credit: Ebola virus virion by CDC microbiologist Cynthia Goldsmith. Public domain via Wikimedia Commons.

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