Have you traveled anywhere recently?

This is a very important question for your healthcare provider, especially if you are showing signs of foreign or respiratory illnesses. Once routine infections have been considered based on the symptoms you display, differential diagnosis will be carried out and this should also include your travel history in order to rule out travel-related infections.

Why is your travel history important?

International travel increases your risk of acquiring infectious diseases not endemic to your home country. About 2 out of 3 travelers get sick while they’re traveling or soon after their return, and somewhere between 3% - 19% of travelers to developing countries will develop a fever. An estimated 15% to 70% of international travelers returning back to the United States have a travel-related illness.

The likelihood of developing a medical condition during travel relates to an individual’s past medical history, travel destination, duration of travel, level of accommodation, immunization history, adherence to indicated chemoprophylactic regimens (i.e. the administration of drug to prevent the development of a disease), activities during travel, and especially to his or her history of exposure to infectious agents prior to and during travel.

All these make it very important for you medical practitioner to have access to your travel records in order to determine whether or not you have been infected by a foreign diseases.

Increased international travel has also concomitantly increased post travel-related diseases, such as respiratory illnesses. Identifying the cause of the post travel respiratory illness is a complex challenge for many healthcare professionals because similar symptoms can occur for both infectious and noninfectious causes. Not only is diagnosis important but it is also essential to prevent transmission. This has been most relevant in the last two decades, where we have seen several severe infectious respiratory syndromes that have spread through international travel causing epidemics in many countries; especially relevant now as we face the COVID-19 pandemic.

Some diseases like Malaria, Dengue, Ebola, and Zyka can also be imported. That means that they can be acquired abroad and brought back to your country in unsuspecting individuals. This is serious and you might be surprised to learn that Malaria is responsible for more morbidity and mortality worldwide than any other illness.

Pre-travel Preparation

If you’re a frequent traveler you will already know that you will be required to take vaccinations depending on your travel destination. This is because you may come into contact with diseases that are rare in the United States, like yellow fever. Getting vaccinated will help keep you safe and healthy while you’re traveling. It will also help make sure that you don’t bring any serious diseases home to your family, friends, and community.

Proper administration of vaccines against hepatitis A, hepatitis B, and yellow fever effectively rules out these infections. However, immune globulin as a preventive for hepatitis A and vaccines against typhoid fever are only about 70% effective; therefore, hepatitis A and typhoid fever still should be considered in patients who have been immunized with these agents.

Childhood vaccination against diseases such as polio, diphtheria, or measles may not provide adequate protection in adults unless a booster dose has been administered or natural disease has been reported. We must also consider that immigrants from developing countries may not have received routine immunizations.

If a patient recently has traveled to an area where malaria is endemic, the physician should determine whether personal protective measures (e.g., insect repellents, bed nets) and chemoprophylaxis were used. Although these measures decrease the risk of acquiring malaria, no antimalarial chemoprophylactic regimen is completely protective. Poor adherence with antimalarial drug regimens is the main documented cause for travelers who contract malaria.

The health of the patient before travel also is important. The presence of underlying medical conditions (e.g., cardiopulmonary disease, immunosuppression, asplenia) may increase susceptibility to various infections. Furthermore, it should also be noted that medications taken for treatment of an underlying condition may alter the presentation of certain diseases.

Incubation Period

Your physician may be able to estimate the incubation period for a patient's illness based on the order of the symptoms, travel history and exposures. This can help narrow the differential diagnosis by highlighting or eliminating certain infections.

Symptoms of dengue fever, typhus, and viral hemorrhagic fever usually begin within 10 days of exposure. Typhoid fever may present up to 21 days after exposure to contaminated food or drink. The usual incubation period for P. falciparum malaria ranges from 8 to 40 days, but infection with the other three Plasmodium species that cause malaria (i.e., Plasmodium vivax, Plasmodium ovale, and Plasmodium malariae) may not become clinically apparent for several months or even years after exposure. In addition, the usual incubation period for malaria can be lengthened if the patient has taken antimalarial medications.

Conclusion

The investigation of a febrile traveler recently returned from a developing country requires detailed knowledge of the patient’s pre-travel preparation, travel itinerary and exposure history. In addition, knowledge of the global epidemiology of infectious disease and the techniques required to make a diagnosis are invaluable. It is possible that the traveler may not be suffering from an infection contracted during travel at all, however, the workup-of such patients should always be considered a medical emergency and, where indicated, "malaria until proven otherwise". Infectious disease or tropical medicine specialists should be consulted immediately when such expertise is required.