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Germs that infect humans

Escherichia coli strain 0157:H7

Escherichia coli strain 0157:H7

© Dennis Kunkel Microscopy, Inc.

Microorganism: the bacterium Escherichia coli, strain 0157:H7.

Disease: hamburger disease

Occurrence of the disease

History: the 0157: H7 strain of E. coli was isolated from patients suffering from hemorrhagic colitis (bloody diarrhea) during an epidemic in the United States in 1982.

Current situation: in 1998, Quebec and Ontario were the two provinces reporting the greatest number of cases of drinking water contamination by verotoxigenic E. coli and of hamburger disease - 378 cases were reported in Quebec alone. In May and June of 2000, 2,000 people became sick and 21 people died when this strain of E. coli contaminated the water supply of Walkerton, Ontario.

Mechanism of action of the microorganism: in the intestine, the bacteria produce a toxic substance that causes diarrhea.

Symptoms of the disease: in serious cases, bloody diarrhea.

Incubation period: two to eight days.

Contagious period: one to three weeks.

Hosts: cattle are the largest host population, although humans can also act as hosts in some cases. There is some evidence that North American deer are also hosts.

Transmission: primarily by ingestion of contaminated food, especially incompletely cooked minced beef. Transmission may also be by oral-fecal contact.

Treatment: rehydration. Antibacterial agents are of little use and recent studies have shown that their use may even be harmful in some cases.

Geographical distribution of the microorganism: North America, southern South America, Europe, Japan, and Australia.

Prevention: complete cooking of minced meat; regular hand washing.

Vaccine: none.