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Geographic Distribution

It is estimated that up to 20% of the world's population harbor amebae, although only a small number (probably 5% or 6%) of these hosts develop invasive (and thus clinical) amebiasis. The parasite is found throughout the world, but is considered endemic between parallels 40 North and 30 South. Areas with the highest E. histolytica endemic activity include Asia, India, East and South Africa, Mexico, and portions of Central and South America. Thus, in Colombia 45% of the population may be infected, in Mexico 20%, and in Venezuela 17%. In Egypt (Cairo), estimates vary from 20% to 40% of the population, and in India from 10% to 15%. St. Petersburg, Russia has a surprisingly high rate of infection for a nontropical city.

Logically, the incidence of amebiasis in the industrialized countries of Europe and North America is low. In the United States, it is currently estimated that less than 1% of the population may harbor amebae; however, as recently as 1967, over 12% of stools from 149 U. S. Army medical officers who had never been out of the United States contained E. histolytica. Subsets of the population may show an unusually high incidence of amebiasis, particularly homosexual patients who attend sexually transmissible disease clinics. Pomerantz reported 1,875 amebiasis cases among the homosexual community in New York, a higher number, even than for tuberculosis (1,307 cases) or hepatitis (1,260 cases). Other studies of New York City male homosexuals have found between 19.6% and 31.7% of these patients to be infected with E. histolytica.

The existence of amebiasis in a community can be considered representative of the pathology of poverty, which implies deficiencies in the elemental rules of hygiene, lack of proper sewer systems, and irrigation with black or untreated waters. Therefore, it occurs primarily in developing overpopulated countries, even though it is a cosmopolitan disease that can be found in any part of the world in which humans and the parasite coexist. Certainly amebiasis is a common disease, although some of the above estimates appear high (... we hope!).

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