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- Materials and Methods
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Background. About 50 million people travel each year from industrialized countries to destinations in the tropics and subtropics. Among them, there are more than 2 million minors traveling. Although their number is increasing constantly, data on health risks during travel are limited.
Methods. This study analyzed demographic, travel, and clinical data of 890 travelers of age <20 years presenting at the outpatient travel clinic of the University of Munich between 1999 and 2009 after returning from the tropics and subtropics.
Results. Most (87%) of these young travelers were born in Germany. Among them, the main travel destination was Africa (46%), followed by Asia (35%) and Latin America (19%). The most frequent syndrome groups were acute diarrhea (25%, especially in age 0–4 y), dermatologic disorders (21%, especially in age 0–9 y), febrile/systemic diseases (20%), respiratory disorders (8%), chronic diarrhea (5%), and genitourinary disorders (3%). The 10 most frequent diagnosed infectious diseases were giardiasis (8%), schistosomiasis (4%), superinfected insect bites (4%), Campylobacter enteritis (4%), Salmonella enteritis (4%), cutaneous larva migrans (3%), amebiasis (3%), dengue fever (2%), mononucleosis (2%), and malaria (2%). The relative risk (RR) for acquiring any infectious disease during travel was highest in Central, West, and East Africa, followed by South America, South Asia, and Southeast Asia.
Conclusions. Age of young travelers and destination of travel were the most important variables being strongly correlated with the risk for acquiring infectious diseases in the tropics and subtropics. The highest risk was carried by very young travelers and those staying in sub-Saharan Africa (except Southern Africa).
According to the United Nations World Tourism Organization, more than 935 million international travels occurred in 2010 and their number is increasing continuously.1 About 50 million people travel each year from industrialized countries to tropical or subtropical destinations.2 Although estimations on the number of children traveling internationally are limited, travel data for US residents indicate that about 1.5 to 2 million US Americans of age under 16 years travel annually to tropical or subtropical countries.3,4 In the UK, imported diseases account for 2% of pediatric hospitalization.5 Physicians have to be aware that potential pathogens differ in various factors, such as the population of travelers,6,7 the travel destination,8,9 and the incubation period of pathogens typical or specific for the tropics and subtropics.10–12
Travel medicine standards are increasingly based on evidence and moving away from reliance on single expert opinions. Nevertheless, previous studies on pediatric travel-related morbidity were using post-travel questionnaires13,14 or consisted only of small study populations from single centers with focus on individual diseases.15–20 A certain number of multicentric reviews were performed; however, most of them focused on the demographic characteristics21 and on diagnoses without linking them to the symptoms presented by young patients returning from travel.
This study analyzes systematically demographic, travel, and clinical data of travelers of age <20 years returning from tropical and subtropical countries and presenting at the outpatient travel clinic of the Department of Infectious Diseases and Tropical Medicine (DITM) in Munich, Germany. Stratified into age groups, the study describes the spectrum of imported infectious diseases and syndromes among the study population. Furthermore, it evaluates the risk for acquiring infectious diseases and syndromes for different travel destinations.
- Top of page
- Materials and Methods
- Declaration of Interests
This is one of the largest studies on imported infectious diseases among young travelers returning from tropical and subtropical countries. The study analyzed demographic, travel, and clinical data of travelers of age <20 years and assessed risk factors for acquiring infectious diseases during traveling after stratifying the data into four age groups. Out of 2,558 individuals of age <20 years presenting at the outpatient travel clinic of the University of Munich between 1999 and 2009, 890 travelers (35%) returned from tropical and subtropical destinations and had a clinically or laboratory confirmed diagnosis.
The variable sex was not significantly correlated with any imported infectious disease, whereas it seemed to be for the variables age and origin. Consequently, data were analyzed by stratifying into age groups and further analysis was performed with travelers of German origin only to avoid confounding. However, 30% of young travelers born in Germany were abroad for visiting friends and relatives, thus we suppose that the majority of these travelers have parents who had migrated to Germany before.
Analysis on travelers with German origin has not shown any significant correlation between type of travel and acquired infectious disease; also there was no significant correlation found between the type of travel “visiting friends and relatives” and destination or the risk to acquire a certain infectious disease. Among 48 travelers of African origin, almost all (47: 98%) traveled to Africa and acquired infectious diseases which are highly endemic there, such as malaria (5 cases), schistosomiasis (6 cases), and diarrheal diseases (23 cases). The correlation between African origin and these infectious diseases was highly confounded by travel destination. For travelers with other origins, sample size was low and no correlation with any infectious disease was found.
Among the very young travelers of age 0 to 4 years, the duration of travel was significantly longer than that for travelers of age 5 to 19 years. This result was caused by the fact that almost half of the parents with children of age 0 to 4 years stayed abroad for visiting friends and relatives. In the age group 0 to 4 years, the risk for diarrhea, especially acute diarrhea, was higher than in the age group 5 to 14 years, as shown in other studies.21,22
Among the travelers of age 5 to 9 years, the risk for acquiring schistosomiasis was significantly higher than that for travelers of the other age groups. This result is caused by the fact that more travelers in that age group stayed in Africa, where schistosomiasis is highly endemic in many regions.
In this study, the following trends depending on the age of young travelers were found. With decreasing age, there was an increasing duration of travel, increasing number of travelers visiting friends and relatives abroad, and increasing risk for acquiring acute diarrhea and dermatologic disorders during travel. Furthermore, with increasing age, there was an increasing number of backpackers (as teenagers prefer traveling by backpacking) and increasing risk for acquiring mononucleosis (as teenagers have an elevated risk mainly caused by kissing) abroad.
Besides mononucleosis, dengue fever and malaria were the most frequently detected febrile/systemic diseases, whereas the majority of dengue fever cases were imported by young travelers from Asia (especially in age group 10–14 y) and the majority of malaria cases from sub-Saharan Africa with steady pattern of distribution among the age groups.23
Dermatologic disorders were mainly caused by insect bites and cutaneous larva migrans, which are diseases that can be prevented by some simple precaution.24,25 However, the number of causes for dermatologic disorders was large and an elevated risk for travelers <10 years.
In general, children of age <10 years showed a distribution pattern of infectious diseases and syndrome groups similar to the one described by previous studies about pediatric travelers6,21 while travelers of age 10 to 19 years matched the distribution patterns found in adults (own unpublished data from about 20,000 returned adult travelers).6,8
The principal variable influencing the risk for acquiring infectious diseases among young travelers was destination of travel. The highest overall risk was carried by young travelers staying in Central, West, and Eastern Africa, followed by South America and South/Southeast Asia. In sub-Saharan Africa (except Southern Africa) and South/Southeast Asia, the most frequent health problems among young travelers were diarrhea and febrile/systemic diseases, mainly due to an elevated risk for malaria in sub-Saharan Africa (except Southern Africa) and for dengue fever in South/Southeast Asia, whereas for young travelers in South America, diarrhea and dermatologic disorders were the most frequent health problems. All these findings correspond to those of other studies.21,26–29
This study had some limitations. Like in previous studies30,31 it was difficult to make specific etiologic diagnoses for all occurred symptoms, especially for diarrhea in which almost 40% of the cases were diagnosed with gastroenteritis, presumably caused by an viral infection.32 No specific diagnostic procedures on rotavirus, norovirus, and Escherichia coli spp. were performed, although these pathogens are frequent causes of travelers' diarrhea.26 However, in contrast to the other studies on large numbers of patients, which were mostly multicentric,7,21 this study provides same conditions for all patients, consistency in coding of diagnoses by clinicians, and central laboratory reference facilities.
Among all variables analyzed in this study, destination of travel and age of traveler were variables highly correlated with the risk for acquiring infectious diseases, which are specific or typical for the tropics and subtropics. Very young travelers were more likely to stay abroad for a long time, to visit friends and relatives, and to carry a higher risk for acquiring acute diarrhea and dermatologic disorders during travel, while travelers of age 10 to 19 years matched the distribution patterns found in adults. The highest overall risk was carried by young travelers staying in sub-Saharan Africa (except Southern Africa).