What Is Diseases of Travelers?
Removing the human body from an environment to which it is acclimated poses risks:
- Exposure to endemic illnesses in a new environment
- Illness during travel
- Illness from the rigors of travel
Exposure to Illnesses Endemic in Travel Destinations
In areas to which one is not accustomed immunologically, there is risk from both pathogenic infectious agents and the non-pathogenic infectious agents. The typical microbiome of a travel destination can exchange normal bacteria (e.g., E. coli) with portions of the traveler’s microbiome, causing gastrointestinal illness.
The pathogenic infectious organisms there can afflict newcomers vehemently. This can occur even with infections that affect the native population only minimally. Other bacteria, viruses, and parasites pose a threat to the unprepared traveler.
Travelers diarrhea, the most common illness, affecting almost 40% of those traveling from a resource-rich to a resource-poor region, is usually self-limited requiring only support. There are numerous bacterial, viral, and parasitic organisms that can cause this. E.coli generally causes malaise, anorexia, abdominal cramps, and watery diarrhea. Other causes include Salmonella, Shigella, and Vibrio bacteria; norovirus; and Giardia, Cyclospora, and Entamoeba parasites.
Malaria, dengue fever, Chikungunya fever, typhus, leishmaniasis, and yellow fever are vector caused, e.g., mosquito bites. Travelers’ diarrhea, typhoid, brucellosis, hepatitis A, leptospirosis, cholera, and polio are risks of improperly prepared food or tainted water. Snake bites, parasitic entry, and marine hazards (jellyfish, bites, etc.) add to the usual increase in accidents abroad, especially automobile accidents when unaccustomed to strange rules, road signs and signals, and distractions, such as map reading.
Illness During Travel
Many travelers, especially elderly travelers, travel with ongoing illnesses or conditions that are chronically treated, such as heart and other cardiovascular disease, diabetes, renal or liver disease, etc. Altitude reduces barometric and oxygen pressure which can challenge one’s cardiovascular system and may affect pacemaker thresholds. Crossing several time zones can interfere with a diabetic patient’s insulin schedule; sporadic eating necessitated by the rigors of travel can alter insulin needs creating the risk or hyperglycemia or insulin shock.
Travel to other areas or exotic destinations will deprive those with chronic conditions the care needed should they suffer complications; at the very least, immersion in a foreign healthcare system will make timely treatment more difficult.
Persons at risk for deep vein thrombosis may put themselves at risk with lengthy transportation, such as prolonged air, train, or bus travel. Motion sickness is always possible in moving vehicles of any kind, especially boats. Cruise ships in particular offer a new type of “institutionalized” setting in which outbreaks of gastrointestinal disease are characterized by resistances seen in hospitals and other institutions. Pregnant patient should respect additional precautions (e.g., Zika virus) or the risk of going into labor in a strange or undeveloped area.
The incubation periods of infectious diseases can be long enough to delay onset of symptoms until return home, confusing the diagnosis.
Illness Due to the Rigors of Travel
Jet lag and other disruptions to one’s circadian rhythm can compromise the immune system, lowering the threshold for becoming ill and compromising the ability to resist or fight disease, as well as impact the travel plans due to excessive fatigue.
How Can Diseases of Travelers Be Diagnosed?
The diagnoses and tests that seek to identify illness are focused on the area of travel and based on the signs and symptoms.
For Travel To:
- South Asia: Tests for the mosquito-borne diseases–malaria, dengue fever, Japanese encephalitis, Chikungunya fever; typhus and Leishmaniasis from fleas and flies, respectively; typhoid fever (Salmonella), Brucellosis (raw milk), and hepatitis A & E from food/water contamination; and Leptospirosis from infected water. (Polio is endemic in Pakistan and Afghanistan.)
- Africa: Tests for HIV, diarrheal diseases, malaria, tuberculosis, Ebola, yellow fever, Schistosomiasis, Lassa fever, foot-and-mouth disease, and typhus.
- South America: Tests for malaria, yellow fever, dengue fever, Chikungunya, West Nile virus, Eastern and Western Equine Encephalitis, and Zika virus.
- Latin America/Caribbean: Dengue fever, cholera, Venezuelan Equine Encephalitis, and leptospirosis,
- Mexico: Tests for dengue, Chikungunya, Zika, malaria, parasites, tuberculosis, traveler’s diarrhea, and hepatitis A.
Depending on the area of travel and the signs and symptoms with which a patient presents, the testing can include blood work, cultures, fecal and urine exams, CT imaging, and at times, biopsies of skin, lung, and liver.
Examination of the blood can reveal red blood cell abnormalities, such as is seen in malaria, stages of parasitic life cycles, evidence of protozoans, and electrolyte abnormalities due to excessive diarrhea or nausea/vomiting.
Examination of stool can demonstrate eggs, worms, and all stages between for parasitic helminths and protozoans.
In rare cases, the diagnosis can remain elusive until actual biopsies are performed to look for evidence of infestation.
How Can Diseases of Travelers Be Managed?
Management of diseases acquired abroad involves maintenance of electrolytes or anemia due to the symptoms. Some organisms have no treatment and a physician is limited to management of complications only.
- Respiratory compromise may require oxygen supplementation and perhaps even mechanical support
- Blood infections will require treatment for anemia or for hemorrhagic infections to prevent life-threatening coagulation problems
- GI manifestations will require fluid and electrolyte maintenance of homeostasis
Any of these can create a need for isolation if the infections are communicable.
Actual treatment, when applicable, involves the eradication of the infecting organism. Antibacterial, antiviral, anthelmintic and other medications are used, depending on the diagnosis. Some infections are self-limited, such that maintenance of homeostasis is all that is required until the patient is out of clinical danger.
To prevent illness while traveling, it is good preventative strategy to have a pre-travel evaluation with one’s primary care physician. He or she can advise upon many conditions that are present and how best to avoid complications that traveling add to their respective risks. A list of potential exposures based on the itinerary can help organize immunizations/vaccinations to preemptively counter the endemic diseases along the trip and at the destination.
A list of all current conditions and current medications should be compiled. For the medications, include the generic names, since brand names may be unrecognized abroad.
A past medical history and a list of allergies is part of the pre-travel evaluation, as is a list of immunizations and the dates of administration.
Ingestion of Contaminated Food and Drink
Travelers diarrhea, the most common illness, affecting almost 40% of those traveling from a resource-rich to a resource-poor region, is typically caused by ingesting any one of many bacterial, viral, and parasitic organisms. Avoiding open-air food establishments and keeping to factory-sealed bottles of beverages can limit exposure.
Standing and walking should be done at least every 1-2 hours to discourage thrombus formation in the legs. Jets do not pressurize cabins to sea level, so that cardiopulmonary compromise may require pre-trip planning for oxygen supplementation. In those with respiratory infections, decongestants will help prevent ascent or descent pain in the eustachian tubes. Jet lag should account for the time of re-equilibration with one’s circadian rhythm, typically one day for each time zone crossed. Some immunocompromise and fatigue from disruption of the sleep/wake cycle can be anticipated. For this reason, in west-to-east travel, melatonin should be taken on the evening of arrival and for 5 days after; in east-to-west travel, seeking morning light and avoiding sun exposure in the afternoons for a few days will ease the re-acclimation. Diabetics should discuss alterations in their insulin requirements due to jumped time zones and sporadic meals.
The CDC has information on which specific cruise ships meet sanitation standards. Hand-washing should be frequent. Scuba divers should wait 1-2 days before flying to avoid decompression sickness (“the bends”).
The biggest risk in traveling to remote locations (ocean travel, jungle expeditions, desert travel) is the lack of a timely response to medical emergencies that can arise. One must take into account present medical conditions that would rely on a timely intervention should it be necessary. Even surprises (e.g., appendicitis on the tundra) can cause death that otherwise could be treated easily.
Vaccines needed will depend on the destination. However, the following are commonly administered:
- Yellow fever (Africa, Central and South America)
- Typhoid (Asia, Africa, Latin America)
- Hepatitis A
- Japanese encephalitis (Asia)
- Polio (Pakistan and Afghanistan)
- Tetanus, diphtheria
- Hepatitis B
An egg allergy should be reported before getting any immunizations. Also, some vaccines require more than one dose, so the time needed for a full course completion before embarking should be taken into account.