For Asia, rates for typhoid fever and shigellosis declined, whereas rates for hepatitis A remained stable. This finding may reflect the disproportionate impact of the Indian subcontinent, with stable trends, on trends for Asia overall: 75% of all Asian hepatitis A cases were contracted in the Indian subcontinent, compared to <60% for shigellosis and typhoid fever (data not shown). The trends in attack rates we found
for hepatitis A and typhoid fever correlate with findings in other studies.5–7 One study on travel-related shigellosis discusses only absolute attack rates; these correlate with the median rates we calculated.17 The Dutch policy not to recommend typhoid fever vaccination for Ivacaftor short-term travelers to Latin America, Eastern/Southern Sub-Saharan Africa, Turkey, and Thailand/Malaysia appears to be justified, because
median attack rates for these destinations were less than 0.2 per 100,000 travelers (Table 2), and vaccine-failure occurred in at least 21% of cases (Table 1). This study has some possible limitations. Although the three infections are comparable in their mode of transmission, they differ in ways that influence reporting. For example, the short incubation period for shigellosis (1–7 d) as opposed to hepatitis A (2–7 wk) increases its chance Y-27632 chemical structure of occurring abroad, decreasing its chance of being reported in the Netherlands. Also, the three diseases differ in degree of asymptomatic infection, patients’ medical attention-seeking behavior, and doctors’ tendency to request laboratory confirmation. Hepatitis A virus infection in childhood is often asymptomatic, but occurs with varying severity of illness in adults. In typical shigellosis, stools contain blood and mucus, but may also present as watery diarrhea or asymptomatic infection. Typhoid fever symptoms can likewise range from asymptomatic to severe. Susceptibility for the latter two increases in a setting of gastric achlorhydria or immunosuppression. These variations in disease severity undoubtedly influence the chance of being diagnosed,
and thus the chance of being reported. However, there are no reasons to believe that the impact of these factors changed during the study period. Thus, they have led only to an underestimation of the annual Fluorouracil attack rates, without affecting trends in attack rates. Serology is not an accurate method for the diagnosis of typhoid fever, because of cross-reactivity. However, the proportion of serological confirmed cases was low (6.4%), and it did not change during the study period. Thus, trends in attack rates were not affected. In our study, the number of annually reported cases was put into perspective by using numbers of travelers as denominators. The latter are crude estimates. Country-specific data were used after classification into regions to render findings more robust.