Distribution and Incidence

Since the beginning of the twentieth century, typhoid fever has been largely a disease of the developing world, and the same factors that interfere with the provision of health care in these regions also interfere with the gathering of health statistics.

For northern Europe, North America, Japan, and Australia, the annual incidence of typhoid fever is less than 1 case per 100,000 persons, and half of these cases are acquired by foreign travel rather than by indigenous exposure. The annual incidence in southern and eastern Europe averages about 10 per 100,000, whereas in the developing world it is 40 in Egypt, 100 in Chile, 850 in rural South Africa, and ranges from 500 to 1,000 for some areas of South and Southeast Asia.

These crude estimates in turn suggest that the global incidence averages 300 cases of typhoid fever per 100,000 persons per year or 15 million cases of typhoid fever each year.

Regarding age, sex, and race, the following generalizations can be made: In endemic areas, 75 percent of cases of typhoid fever occur in persons 3 to 18 years old. Typhoid is only rarely described in children younger than 2 years, although studies in Chile indicate that typhoid fever may be unsuspected clinically because the characteristic features of the disease are blurred in this age group. For acute typhoid fever, the ratio of the sexes is equal, but three-quarters of carriers are women; no susceptibility to typhoid fever has been identified by race.

Poverty is usually associated with poor sanitation and poor health care, and thus constitutes a risk factor for acquisition of typhoid. Blacks in South Africa have four times the incidence of typhoid, with eight times the mortality rate of whites. In Israel, the rate for the Jewish population is similar to that for Europe; for the non-Jewish population, it is similar to that for the Middle East.

In endemic areas, typhoid tends to peak in the summer months. Whether this pattern is due to greater consumption of water or enhanced proliferation of the bacteria in food is unknown. In the developed world, to judge by the United States, seasonality reflects foreign travel patterns, with peaks in January and February and again in the summer months.

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