Shigellosis

Shigella is a Gram-negative, non-motile bacillus belonging to the Enterobacteriaceae family. There are four species of Shigellae: S. dysenteriae, S. flexneri, S. boydii and S. sonnei (designated as serogroups A, B, C and D respectively).

Shigellosis is an acute invasive enteric infection caused by bacteria belonging to the genus Shigella; it is clinically manifested by diarrhoea that is frequently bloody. Shigellosis is endemic in many developing countries and also occurs in epidemics causing considerable morbidity and mortality.

It is estimated to cause at least 80 million cases of bloody diarrhoea and 700,000 deaths each year, the majority of cases (~70%), and of deaths (~60%), occur among children less than five years of age. Shigellosis usually strikes between twelve and fifty hours after the contaminated food is consumed.

It can cause abdominal pain, cramps, diarrhea, fever and vomiting. Shigellosis occurs predominantly in developing countries due to overcrowding and poor sanitation. Infants, non-breast fed children, children recovering from measles, malnourished children, and adults older than 50 years have a more severe illness and a greater risk of death. Transmission occurs via the faecal-oral route, person-to-person contact, household flies, infected water, and inanimate objects.

Among the four species of Shigella, Shigella dysenteriae type 1 (Sd1) is especially important because it causes the most severe disease and may occur in large regional epidemics.
Shigellosis