Public Health Agency of Canada
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Notifiable Diseases On-Line

SHIGELLOSIS

Shigellosis is an acute intestinal illness caused by bacilli belonging to the genus, Shigella. The infection is spread by the fecal-oral route. Infection then passes either by person-to-person contact or indirectly by contaminated food. Outbreaks are common under conditions of crowding and in circumstances where hygiene practices are poor, such as prisons, daycare centres, mental hospitals and among men who have sex with men.

AGENT OF DISEASE

Shigellosis is caused by bacilli belonging to the Shigella family. The most common subtypes are S. sonnei, S. flexneri, and S. boydii.

SYMPTOMS

The incubation period is brief, usually 1-3 days (range of 12-96 hours). The illness is characterized by diarrhea accompanied by fever, nausea, vomiting, and cramps. In typical cases, the stools may contain blood and mucus, resulting from tiny abscesses on the intestinal wall. Convulsions may be an important complication in children. The severity of illness and the case-fatality rate is influenced by several factors: age of the patient, presence of underlying disease, and the serotype. S. dysenteriae 1 causes the most severe illness and the most severe complications with a death rate as high as 20% among hospitalized cases.

PERIOD OF COMMUNICABILITY

An infected person is capable of transmitting the bacteria as long as the bacteria remain in the feces, usually for 4 weeks after illness.

HOW IT IS TRANSMITTED

The bacteria is transmitted via the fecal-oral route. Person-to-person transmission is most common among children and in circumstances where hygiene practices are poor. In these cases, persons do not wash their hands thoroughly after using the toilet. Subsequently, the infection is transmitted by direct physical touching of the hand(s) or indirectly through contaminated food. Transmission via drinking or recreational water may occur as a result of direct fecal contamination. Flies can transmit enough of the bacteria from waste products to infect food items.

WORLDWIDE DISTRIBUTION

Occurrence is worldwide. It accounts for >600,000 deaths/year, with 2/3 of cases and most deaths occurring in children under 10 years of age. Outbreaks are common, particularly in crowded conditions where sanitation is poor, such as prisons, institutions for children, daycare centres, and mental hospitals, as well as among men who have sex with men . In general, S. flexneri, S. boydii, and S. dysenteriae 1 account for most cases in developing countries. In developed countries, S. sonnei is most common and S. dysenteriae is the least common. Multi-antibiotic resistant strains have appeared worldwide, resulting from wide spread use of antibiotics.

PREVENTION/CONTROL

  1. Always wash hands after using the toilet and before preparing and serving food.
  2. Drink pasteurized milk and dairy products.
  3. Persons who travel to countries where giardiasis is common should seek advice from a travel medicine clinic to assess their personal risk and appropriate preventive measures. Additional information can be obtained from Public Health Agency of Canada Travel Medicine web page.
  4. Travellers to countries where the safety of drinking water is suspect should boil or disinfect and filter water that is to be used for drinking, food preparation, or dental hygiene. Eat only cooked hot foods or fruits you peel yourself.
  5. For more Food Safety Facts on Shigella go to Canadian Food Inspection Agency's website.