A study of 82,825 ill travelers from Europe, North America, Israel, Japan, Australia and New Zealand was published who were interested in staying healthy during exotic travel. They had traveled the world between June 1996 and August 2011. The data was based on the GeoSentinel surveillance network database. There were 3,655 patients (4.4%) who were seriously sick with one of 13 tropical diseases. There were 13 deaths (=0.4%), 10 of which were from malaria. Two died from melioidosis. This is an infectious disease caused by a bacterium found in soil in Southeast Asia (including Thailand, Laos, southern China, Singapore, Malaysia, Burma and Vietnam), Taiwan and northern Australia. One person died from severe dengue. The interesting fact is that there was not a single case of Ebola virus, although this is a highly publicized and lethal illness in Africa. The majority of travelers sustained malaria and typhoid.
The tropical diseases were either due to viral illnesses, bacterial infections or protozoan infections.
Frequent viral illnesses encountered by visitors to Asia were dengue hemorrhagic fever (DHF) or dengue shock syndrome (DSS); avian influenza, Lassa fever as well as other tropical hemorrhagic fevers, Japanese encephalitis including other tropical encephalitis cases, Rift Valley fever and yellow fever.
This is a list of the bacterial infections that were reported: Anthrax, Carrion’s disease (=Bartonella bacilliformis), epidemic typhus, leptospirosis, melioidosis, murine typhus, paratyphoid fever, plague, relapsing fever, scrub typhus, spotted fever group rickettsioses and typhoid fever.
An interesting side-note is that even in familiar places like Hawaii leptospirosis is re-emerging as this link shows. So, it is important for visitors to Kauai and the Big Island of Hawaii (Waipio valley) to refrain from swimming in streams or natural ponds and to not expose your face to cascading waterfalls as leptospirosis can enter through the eyes, the nose, the mouth and scratches on the skin.
Each travel region has its special infection characteristics. With travel to Central America infectious diseases ranked in decreasing frequency like this: typhoid fever, leptospirosis, falciparum malaria and paratyphoid fever. In the Caribbean falciparum malaria was followed by typhoid fever, leptospirosis and paratyphoid fever. In South America the highest on the list was again falciparum malaria, followed by typhoid fever, paratyphoid fever and leptospirosis. In Sub Saharan Africa the highest number of falciparum malaria cases were registered (2633 of them), followed by 42 cases of typhoid fever, paratyphoid fever and leptospirosis. In the Middle East only one case of falciparum malaria, one case of typhoid fever and 2 cases of paratyphoid fever were reported. In contrast there were many more infections reported in South Central Asia (India): 286 cases of typhoid fever, followed by parathyroid fever, falciparum malaria and leptospirosis. All of the cases of typhoid fever and parathyroid fever in India were adequately treated with antibiotics and no deaths resulted from that. This is an example where no vaccine is available for prevention, but swift medical treatment could help immediately when an infection had occurred.
In South East Asia (Malaysia, Philippines, Indonesia) leptospirosis was on top, followed by typhoid fever, falciparum malaria and parathyroid fever. North East Asia (Korea, Mongolia), had only 3 cases of typhoid fever and 1 case of paratyphoid fever. Oceania (Polynesia) reported 26 cases of falciparum malaria, followed by paratyphoid fever and typhoid fever.
Several interesting observations were made with regard to this study.
- Most patients with travel acquired tropical illnesses presented within less than 17 days at the doctor’s office at home and 91% of them had developed a fever.
- The spectrum of the tropical disease that was diagnosed and treated varied according to the geographic destination where the traveler had been, which is consistent with the observations mentioned above (different distribution of tropical diseases depending on which area was traveled). Visitors to West Africa had a high rate of falciparum malaria, visitors to India sustained largely enteric fevers; and leptospirosis, scrub typhus and murine typhus were the dominant tropical diseases for visitors to South East Asia.
- Males were found to be less diligent in using chemoprophylaxis for malaria prior to their travel than females. Overall only a minority had attended a travel clinic prior to their travel for immunizations and chemoprophylaxis for preventable tropical disease such as malaria.
- Other global life-threatening diseases like meningitis, other forms of septicemia, severe bacterial pneumonia and legionnaires also have to be considered as they occurred in roughly 30% of returning travelers.
- Malaria was the largest percentage of the tropical diseases that travelers brought home and 67% of all cases were male patients. They were mostly visiting West Africa where they acquired malaria (typically from Nigeria, Ghana and the Ivory Coast). As mentioned they accounted for 10 of the 13 deaths.
The authors recommend that travelers should prepare themselves for trips to the tropics and subtropics, preferable visiting one of the travelers’ clinics. The recommended procedures should be followed meticulously. Not all of the diseases can be prevented, but if the traveler turns sick, they should seek medical advice as soon as possible in the country where they travel as these physicians often have special expertise in these tropical diseases.
One of the comments of the study was that often people visit relatives and friends in an area where tropical disease exists without any chemoprophylaxis or vaccinations beforehand. The visitors were under the impression that prior living in the area as a child would still protect them now during the travel as an adult, which is not the case. This can be prevented by visiting a travel clinic well before the planned trip, so there is enough time for vaccinations and possible blood tests.
More information on:
1. Traveler’s diarrhea: http://nethealthbook.com/infectious-disease/parasites/travelers-diarrhea/
2. Parasites: http://nethealthbook.com/infectious-disease/parasites/