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Cholera: epidemiology
Last reviewed: 23.04.2024
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The source of the causative agent of cholera is a person (a patient and a vibrio carrier). Especially dangerous are those who remain socially active patients with erased and mild forms of the disease.
The mechanism of transmission of infection is fecal-oral. Transmission ways - water, alimentary, contact-household. The waterway is crucial for the rapid epidemic and pandemic spread of cholera. At the same time, not only drinking water, but also using it for household needs (washing vegetables, fruits, etc.), bathing in an infected reservoir, as well as eating fish, crayfish, shrimp, oysters caught there and not having been heat treated, can lead to cholera infection.
Susceptibility to cholera is universal. In endemic areas, children under the age of 5, with the exception of infants, who get anti-cholera antibodies of IgA class, are predominantly ill. With the development of a cholera outbreak in an endemic region, all age groups are equally affected. Factors contributing to an increased risk of the disease include: a high infectious dose of the causative agent, concomitant conditions associated with hypochlorhydria (malnutrition, atrophic gastritis, including infection caused by Helicobacter pylon, gastrectomy, taking drugs that reduce the acidity of gastric juice), local immunity insufficiency. For unspecified reasons, more severe forms of the disease caused by the E1 Tor biovar are recorded in individuals with 0 (I) blood group.
Forming immunity is short (up to 1 year), type and species-specific, local immunity is of protective value.
After the transferred illness, antimicrobial and antitoxic immunity is produced, which lasts from 1 to 3 years.
The epidemic process is characterized by acute explosive outbreaks, group diseases and individual imported cases. Thanks to extensive transport links, cholera drifts systematically to the territory of countries free from it. Six pandemics of cholera are described. Currently, the seventh pandemic, caused by the vibrio El Tor , continues .
Classical cholera is common in India, Bangladesh, Pakistan, cholera El Tor in Indonesia, Thailand and other countries in Southeast Asia. In Russia, mostly imported cases are recorded. Over the past 20 years, there have been more than 100 cases of importation into seven regions of the country. The main reason for this is tourism (85%). Cases of cholera among foreign citizens are noted. The most severe was the epidemic of cholera in Dagestan in 1994, where 2359 cases were registered. The pilgrims who made hajj to Saudi Arabia brought the infection.
As for all intestinal infections, cholera in temperate climates is characterized by summer-autumn seasonality.
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