Shigella

Recent Outbreaks

Subway Restaurant Shigella Outbreak: An outbreak of shigellosis in Lomabard, IL was traced to a local Subway restaurant.… Continued
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Shigella is a family of bacteria that can cause sudden and severe diarrhea (gastroenteritis) in humans. Shigellosis, the illness caused by the ingestion of Shigella bacteria, is also known as bacillary dysentery.

Ingestion of fewer than 100 Shigella bacteria can cause food poisoning (American Public Health Association [APHA], 2000), making Shigella one of the most communicable and severe forms of the bacterial-induced diarrheas (Gomez et al., 2002).

Shigella thrives in the human intestine and is commonly spread both through food and person-to-person contact.

Shigella is the third most common pathogen transmitted through food. In FoodNet surveillance areas in 2008, the rate of Shigella food poisoning was 6.6 per 100,000 population, exceeded only by Salmonella (15.2/100,000) and Campylobacter (12.7/100,000) (CDC, 2009c).

Shigella is also responsible for a substantial portion of foodborne outbreaks on cruise ships. In a review of cruise ship outbreaks worldwide over several years, 16% of outbreaks were attributed to Shigella, affecting over 2,000 passengers (Rooney et al., 2004). Sanitation violations related to food handling and communicable disease have decreased substantially over the past 15 years (Cramer et al., 2008).

How is Shigella transmitted?

Shigella bacteria are present in the stools of infected persons while they are sick and for up to a week or two afterwards (CDC, 2009a). Most Shigella infections are passed through the fecal-oral route. This happens when basic hygiene and handwashing habits are inadequate and can happen during certain types of sexual activity.

Shigella outbreaks are particularly likely to occur among toddlers who are not fully toilet-trained. Family members and playmates of such children are at high risk of becoming infected.

Shigella food poisoning may be acquired from eating contaminated food, although contaminated food usually looks and smells normal.

Infected food handlers who don’t wash their hands with soap after using the bathroom may contaminate food.
Vegetables can become contaminated if they are harvested from a field with sewage in it.
Flies can breed in infected feces and then contaminate food.
Water may become contaminated with Shigella bacteria if sewage goes into it or if someone with shigellosis swims in or plays with the water (especially in splash tables, untreated wading pools, or shallow play fountains used by daycare centers). Shigella infections can then be acquired by drinking, swimming in, or playing with the contaminated water.
Outbreaks of shigellosis have also occurred among men who have sex with men (Gupta et al., 2004).

The Discovery of Shigella Bacteria

Shigella bacteria are named after Kiyoshi Shiga, a Japanese scientist who discovered Shigella dysenteriae type 1 in 1896 during a large epidemic of dysentery in Japan (Keusch & Acheson, 1996). Since that time, several types of Shigella bacteria have been discovered – S. dysenteriae, S. flexneri, S. boydii, and S. sonnei – all named after the lead workers who discovered them (Centers for Disease Control and Prevention [CDC], 2009a).

S. sonnei, also known as Group D Shigella, accounts for over two-thirds of shigellosis in the United States. Shigella flexneri, or group B Shigella, accounts for almost all the rest.
In developing countries, S. flexneri is the most predominant cause of shigellosis, but S. dysenteriae type 1 is the most frequent cause of epidemic and endemic disease.

Next: Symptoms & Risks »

Shigella

How is Shigella transmitted?

The Discovery of Shigella Bacteria

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