Shigella - Shigellosis Factsheets

What is Shigellosis?
Shigellosis is a bacterial infection affecting the intestinal tract. It is caused by the bacterium Shigella. There are four varieties of this bacterium S. sonnei, S. boydii, S. flexneri and S. dysenteriae. S. dysenteriae produces a very powerful toxin that produces severe damage to the lining of the gut. The bacteria are only found in humans. Anyone can be infected but children are particularly prone. The bacteria cannot survive for long outside the human body.

How is Shigellosis spread?
Shigellosis infection occurs when the bacteria are ingested, which most commonly occurs in close person-to person contact. Contaminated water is an important method of transmission also. People with shigellosis may have no symptoms but can still carry the infection in their faeces. They can pass the infection to others if they do not wash their hands properly after going to the toilet or changing the nappy of an infected infant. They can then contaminate objects that are touched by others or food or drink that is consumed by others.

Who is at risk of developing Shigellosis?
Anyone can get shigellosis, but those who are at greater risk include children in child care centres and their parents, overseas travellers, institutionalized people and men who have sex with men. Outbreaks are common in conditions of overcrowding or poor sanitation.

What are the symptoms of Shigellosis?
Symptoms occur between 1 - 7 days (usually 1 - 3 days) after exposure to Shigella and usually last for 7-14 days. Symptoms include:

• diarrhoea (usually containing mucus and/or blood)
• nausea and vomiting
• fever
• stomach cramps

Severe infections are seen in the very young, the elderly and malnourished people. S. sonnei tends to produce milder symptoms while infection with S. dysenteriae tends to be severe and prolonged and requiring hospital admission. Complications can result in blood poisoning and kidney failure (haemolytic uraemic syndrome).

How common is Shigellosis?
Shigellosis is quite a common disease, between 50 and 70 cases are seen each year in Ireland. Shigellosis is a notifiable disease in Ireland.

How is Shigellosis diagnosed?
Diagnosis is based on finding Shigella in a sample of the patients stool.

What is the treatment for Shigellosis?
For Shigella sonnei, simple measures such as rehydration are all that are required. The more severe forms however require treatment with antibiotics, usually ciprofloxacin. 

Can Shigellosis be prevented?
The best ways to protect yourself again shigellosis is to ensure that you wash your hands regularly and take care when preparing food.

Last updated: 2 July 2010