Introduction
The surge in international travel, transnational business, and reliance on imported goods has escalated the risk of infectious diseases and their vectors entering and spreading within the United States. Previously localized diseases now travel effortlessly across borders due to global interconnectivity in commerce, agriculture, tourism, and employment. This surge in travel-related infections demands a comprehensive response beyond traditional public health measures, encompassing heightened awareness, improved surveillance, and collaborative efforts involving medical and non-medical resources. This article sheds light on such travel-related infections and prevention strategies.
What Are the Common Travel-Related Infections?
The susceptibility of international travelers to various risks hinges on factors such as the destination, trip purpose, itinerary, available resources, accommodations, hygiene practices, sanitation standards, personal behaviors, inherent immunity, and vaccinations. Unfortunately, comprehensive pre-travel guidance in this regard is often lacking. Taking general precautions can mitigate exposure to infection risks. Among these, traveler's diarrhea is the most prevalent infectious ailment affecting travelers, with multiple food and waterborne pathogens possibly implicated. Understanding the pathways of infectious disease transmission offers opportunities for prevention. These modes include the following:
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Food-borne transmission (due to raw or undercooked foods).
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Waterborne transmission (with ice cubes, local restaurant water, stagnant water, and rivers).
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Zoonotic transmission (from animals).
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Transmission of sexually transmitted diseases (from local sex workers).
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Blood-borne transmission (by poorly sterilized medical instruments and intravenous drug use).
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Airborne (respiratory) transmission (due to crowds or individuals displaying respiratory symptoms).
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Soil transmission (farm environments and fields can facilitate disease spread; footwear might carry soil, feces, or animal products; proximity to animals and plants can contribute to disease transmission).
Respiratory illnesses are prevalent as community-acquired diseases and notable instances include viruses causing severe viral pneumonitis, as was observed during the emergence of the new coronavirus SARS (severe acute respiratory syndrome). These observations underline the necessity of understanding and actively managing the various transmission pathways to mitigate travel-related infection risks effectively.
What Are the Prevention Strategies for Travel-Related Infections?
Although emergency physicians may not commonly offer pre-travel healthcare within the United States, many professionals engage in international travel themselves. Consequently, it becomes essential for them to acquaint themselves with primary preventive measures applicable both to their well-being and the patients they attend to during their overseas journeys. While the Centers for Disease Control (CDC) release country-specific directives, overarching recommendations encompass vaccination, preventive antibiotics, and safeguards against insect bites or contaminated water sources. For mosquito-borne illnesses, the preventions are as follows:
Bite Prevention:
Individuals traveling to regions prone to malaria, Zika virus, and other mosquito-borne illnesses can mitigate their risk by donning long-sleeved clothing and pants, using bed nets, limiting outdoor activities around twilight, and avoiding travel during rainy seasons.
Chemoprophylaxis:
The choice of medication should factor in local resistance patterns and patient preferences, including travel timing, potential side effects, and medical history. Atovaquone- proguanil, Chloroquine, Doxycycline, Mefloquine, Primaquine, and Tafenoquine medications are endorsed in the USA for malaria prophylaxis, along with specific considerations for each medication. While chemoprophylaxis is the most effective strategy, standby emergency treatment (SBET) has become an alternative for low-risk area travelers who prefer not to take ongoing medication. If fever develops, patients employing SBET should commence prescribed anti-malarial and promptly seek medical evaluation.
Vaccinations:
1. Hepatitis A: Recommended for most international travel, ideally administered at least four weeks before departure, followed by a second dose for sustained immunity after six months.
2. Typhoid Fever: Highly recommended before international travel, available in oral capsules or injection forms. The increasing antibiotic resistance of S. typhi underscores its importance. The live, attenuated vaccine entails an oral capsule taken every other day for four days, completed at least one week before travel. Refrigeration is essential, and consumption should precede a meal by one hour. Not suitable for immunocompromised patients. An inactivated vaccine requires a single intramuscular injection at least two weeks before travel, with boosters every two years.
3. Dengue Vaccine (Dengvaxia): FDA-approved for children aged 9 to 16 in dengue-prone areas (American Samoa, Puerto Rico, US Virgin Islands) with prior laboratory-confirmed dengue infection. Administration to naïve patients increases severe dengue risk upon subsequent exposure. Many endemic countries offer it up to age 45, with three doses spaced every six months.
What Are the Considerations and Workup for Approach to Febrile Travelers?
When the doctor addresses a febrile individual with travel history, vital factors include travel details such as location, timing, interactions, weather, activities, pregnancy, and medical history. Some infections acquired during travel can manifest after several weeks. The healthcare provider will include local common illnesses like influenza in flu season and cover a wide range of diseases for critically ill patients.
Workup strategy hinges on travel location and timing, aiding in identifying the probable diseases. In situations with multiple potential pathogens, a recommended lab workup covers complete blood count with differential, basic metabolic panel, liver function tests, coagulation screen, blood smear, CK (creatine kinase) level, pregnancy test, influenza swab, blood cultures, urinalysis, urine culture, and chest X-ray. While findings may not be definitive, these tests can spot severe illness warning signs and help guide toward the likely causative agent.
Due to overlapping symptoms and delayed diagnostic outcomes, numerous internationally acquired diseases can not be conclusively diagnosed in the emergency department. When deciding on patient disposition, clinicians weigh severe disease indicators for the most probable cause, admitting if warranted. Though many febrile cases can be managed outpatient, the doctor may provide patients with clear return instructions and close follow-up. If the patient's travel history raises dengue risk, the doctor may advise avoiding NSAIDs (non-steroidal anti-inflammatory drugs) until dengue hemorrhagic fever is ruled out.
Conclusion
The potential causes for fever in international travelers are diverse, and often, reaching a definitive diagnosis within the emergency department remains challenging. Furthermore, although the CDC and WHO offer valuable guidance on diagnosis and treatment, these resources might not always be accessible in the emergency setting. As a result, it is crucial to have alternative approaches, especially for critically ill patients. For febrile travelers lacking a precise diagnosis, preliminary laboratory tests can be performed to narrow down possibilities and assess the potential for severe disease development. Identifying the onset of severe disease is paramount, given that these cases are linked with a heightened risk of complications and mortality.
