The main travel purposes of the expatriates reported in the literatures were volunteer work (40-59%) and business (25-41%) [2, 5]. Most expatriates were from Europe (43%) and North America (29%). Frequent travel destinations were Sub-Saharan Africa (34%), South America (16%), and South-Central Asia (14%) [2]. Most expatriates stayed in destination countries over six months. Between 70 and 73% of expatriates had access to health advice prior to departure. Their sources of health information were as follows, specialists (61.8%), general practitioners (7%), and travel agencies (3%) [2, 10]. The majority (73%) of expatriates experienced at least one medical issue within the first month of staying abroad [10]. Hospital admission and repatriation due to health issues were reported at around 4% and 2% respectively [11]. Only 20% of expatriates remained healthy throughout the whole duration of living overseas. Figure 1 shows a summary of the incidence of common health conditions by destination region.

Incidence of health problems reported by destination

Thirty-seven percent of expatriates reported health problems related to infectious diseases [10]. The majority were minor illnesses and only slightly disrupted work and travel plans. Major health problems reported were vector-borne infections (0.5-33.9%) [10,11,12, 15,16,17], sexually transmitted infections (STIs) (0.2-11.1%) [10, 12, 15], and animal bites (0.3-40%) [10, 16] (Fig. 2). The other three predominant syndromes included gastrointestinal problems (up to 80%), dermatologic problems (40%), and respiratory problems (17%) [9,10,11,12, 15,16,17]. .Compared to short-term travelers, expatriates were more likely to be diagnosed with the following diseases: chronic diarrhea (50 per 1,000, OR 1.2, 95% CI 1.04-1.38), Plasmodium falciparum (Pf) malaria (36 per 1,000, OR 1.5, 95% CI 1.26-1.78), Plasmodium vivax (Pv) malaria (19 per 1,000, OR 2.5, 95% CI 1.92-3.17), and tuberculosis (11 per 1,000, OR 3.3, 95% CI 2.33-4.56) [2].

Percentage of Health Problems among Long-term Expatriate Living Overseas

The incidence of infectious related health problems was 23% among ill returned travelers seen at the GeoSentinel clinic after visiting Asia and the Pacific. Common problems were febrile illnesses (155-224 per 1,000), dengue infection (52 per 1,000), malaria (51 per 1,000), rabies exposure (7 per 1,000), parasitic infections (1-16 per 1,000) and STDs/HIV (5-29 per 1,000) [2, 5, 16]. (Table 1). In the case of syndromic problems, 7.0-50.0% suffered from a gastrointestinal illness (acute/chronic diarrhea, typhoid, hepatitis-A, E infection), followed by respiratory infections (1.7-17.5%), and dermatologic problems (0.9-15.6%). These included bacterial and fungal infections [9, 10, 15, 16, 18, 19]. (Table 2) When compared to other regions of the world, expatriates traveling to Southeast Asia were three times more likely to have latent tuberculosis (TB), with an incidence of 25 cases per 1,000 [2, 5].

Diarrhea was a common problem particularly among young female (<20 years old) expatriates [2, 12, 13]. Acute diarrhea was reported at 115-243 cases per 1,000 expatriates while chronic diarrhea was lower (86-133 cases per 1,000) [2, 5]. Typhoid fever and gastrointestinal parasites were mainly found in travelers to South-Central Asia. The attack rate was 10 and 8 per 1,000 expatriates, respectively [15] Hepatitis-A was reported at an incidence of only 6 per 1,000 travelers among ill-returned expatriates visiting the Geosentinel clinic [2, 5]. The remainder experienced food poisoning and dysentery [12, 20]. One epidemiologic study of diarrhea in travelers to Thailand reported that Australians and New Zealanders were the most common ethnic group suffering from diarrhea (16%), followed by Europeans (8%) and Americans (7%). The habit of eating outside was linked to an increased risk of diarrhea. The likelihood of this event usually began within the first two weeks of their arrival at their destination [21].

Up to 84% of cases of diarrhea among expatriate workers were associated with parasitic infection [20]. Giardiasis is the most common identifiable parasitic infection found in the Middle East (OR 3.27, P-value < 0.05) and South-Central Asia (OR 1.87) when compared to other continents [2]. The prevalence of intestinal parasites among expatriates was 15% [22]. The most common intestinal parasite found was Giardia spp. at around 22%, followed by Entamoeba spp. (18%), Trichuris spp. (16%), Ascaris spp (16%), and Hookworm (13%) [22].

Dengue infection is the most common vector-borne infection in Asia, especially prevalent in Southeast Asia [15]. The incidence rate among Dutch expatriates living in Asia was 30 per 1,000 person-months of stay [23], while the Geosentinel network revealed a lower incidence (17 cases per 1,000 long-term travelers) [2]. The seroconversion rate was 6.7% among Israeli travelers who stay at least three months in Asia [24, 25]. Non-pf malaria was the second most common vector-borne infection with an incidence of 40 per 1,000 ill returned expatriates [5].

The risk of rabies exposure among expatriates increased with longer duration of stay [2]. Seven percent of Norwegian missionaries who worked in low- and middle- income countries for 4-5 years reported rabies exposure [26]. The incidence of an animal bite, scratch, and lick were 1.7, 1.8, and 6.9 per 1,000 person-months among Japanese expatriates who lived in Thailand, respectively (mainly from dog, cat, and monkey). Fifty-four percent of Japanese expatriates who were bitten by a rabid animal did not seek proper treatment [27]. Moreover, only 10%-34% of expatriates living in Asia received appropriate rabies post-exposure prophylaxis after exposure to rabid animals [28, 29].

Approximately 40% of ill return expatriates from African countries reported new health problems [5]. Common travel destinations for expatriates were sub-Sahara African countries such as Angola, Mozambique, Zambia, Zimbabwe, Uganda, Malawi, and Tanzania [2, 5, 10, 16, 17]. The minority traveled to North, West, and Central Africa [5, 18, 30]. Approximately 214-289 per 1,000 expatriates who stayed in Sub-Saharan Africa (SSA) suffered from febrile systemic illness such as pf malaria (115 per 1,000), filariasis (31 per 1,000), schistosomiasis (from S.mansoni and S.haematobium, 36 per 1,000), HIV infection (5-28 per 1,000), rickettsiosis (4 per 1,000), and leishmaniasis (3 per 1,000), (Table 2) [2, 5, 15, 17, 30, 31]. Eosinophilia was found to be in a significantly higher proportion in long-term travelers with an OR = 4.1, 95% CI (2.5-6.8) followed by schistosomiasis (OR = 3.1, 95% CI (2.1-4.6)) and tuberculosis (OR = 2.4, 95% CI (1.1-5.3) when compared to short-term travelers [2]. During a three-year Portuguese mission in Angola and Mozambique, twenty percent of new health complaints or requests of medical attention were infection-related. Of these, 5% needed hospital admission [17]. In the case of syndromic diseases, gastrointestinal problems were reported at a rate of 53-139 per 1,000, followed by dermatologic problems at 73-88 per 1,000, and respiratory problems such as acute respiratory tract infection and TB at 6-41 per 1,000 expatriates [2, 5].

Human African trypanosomiasis with cutaneous lesions (chancre) or central nervous system involvement was reported in expatriates who traveled to East African countries including Uganda, Tanzania, Malawi, Zambia, and Zimbabwe [31]. Only 21 cases of long-term expatriates were identified and evacuated to South Africa for treatment, of these 38% were occupational-related exposure, e.g., military, business, game ranching, or conservation [31]. Non- native African patients were reported in this study which accumulated information for over 14 years [31].

In general, the risk of getting malaria in Africa was three to four times higher compared to other continents [30]. Living in Africa for more than three months increases the risk of malaria infection four-fold [30]. Therefore, Malaria was a common problem among expatriates living in Africa. A study into ill-returned Voluntary Service Overseas (VSO) reported 12% malarial infection and around 38% of them had symptoms during their travel [12, 30]. Most malaria patients acquired the infections in sub-Saharan Africa [30]. Pf was the most prevalent species, followed by P. vivax and P.ovale. In 2001, a lower rate of malarial infection (8 per 100 PCVs-years) was reported among 8,000 US Peace Corps Volunteer (PCV) serving for two years in Madagascar [32]. A recent study from 1996-2008 by the GeoSentinel clinics showed the incident of Malaria among ill-returned travelers from sub-Saharan Africa to be 68 per 1,000 long-term travelers [2]. However, less than 2% of expatriates had good compliance to malaria chemoprophylaxis in their daily living [14] and 62.5% of ill-returned travelers from tropical countries had poor regime in taking chemoprophylaxis medication during their stay [30]. The International Committee of the Red Cross (ICRC) showed better compliance for malaria prophylaxis medication among specialist and delegate groups [10].

Filarial infection was reported in only 0.62% of travelers who visited the GeoSentinel Surveillance network. This was equal to 31 per 1,000 tong-term travelers [2]. Most patients were immigrants who visited friends and relatives (VFR) while the rest were non-urban expatriates. Onchocerca volvulus was the most common causative organism which accounted for 37%of the infections, followed by Loa Loa (25%), and Wuchereria Bancrofti (25%). The average timing of filarial infection was 125 days after arrival. Within one month of arrival, O.volvulus was regularly detected, whereas L.loa took 1-6 months. The longest lasting species was W. bancrofti (> 6 months) [33]. Patients who were infected in Northern Africa and Sub-Saharan Africa accounted for 75% of total infections [33]. Filarial infection was more likely to be discovered among non-endemic visitors due to the popularity of the destinations [33].

Many factors drove the desire of expatriates to have sexual contact during their stay overseas. These included their young age, single status, willingness to have sex prior to the travel, and feelings of boredom and loneliness [34]. Almost one-third of the ICRC expatriates and 41% of Dutch expatriates engaged in casual sex with local partners [10, 34]. More than half of both groups also reported ever paying for sex [34]. Only 64% reported using condoms consistently with casual and steady local sexual partners [10, 12, 34]. The incidence of STIs was 7% among PCVs in Madagascar. Male expatriates had a greater likelihood than female expatriates of contracting STIs (67% vs 33%) [35]. Among Peace Corps male volunteers, consistent condom use was associated with low alcohol consumption and awareness that HIV was a significant health risk [32]. One piece of research found that expatriates who had African sexual partners had a six-fold increased risk of HIV infection [36]. Furthermore, having more than ten sexual partners increased the risk of HIV infection by 14 times [37].

Expatriates who visited Caribbean, Latin American, and South American regions displayed similar infect