Shigella sp.

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• Hosts
• Transmission/Exposure Routes
• Incubation Times
• Case Fatality Ratios
• Burden of Disease
• Microbiology
• Environmental Survival
• Recommended Dose Response Model

Humans

The disease is transmitted faeco-orally, the commonest modes being person-to-person contact and contaminated food and water. Infected food handlers can spread the disease.

Incubation period of the disease is 1-4 days which is usually followed by sudden onset of acute symptoms.

The overall mortality rate in developed countries is less than 1%. In the Far East and Middle East, the mortality rates for S dysenteriae infections may be as high as 20-25%.(Medscape)

Case Fatality Ratios

Location	Mortality Rate	Reference
Developed Countries	<1%	(Medscape)
Far East/Middle East	20-25%	(Medscape)

The incidence of Shigella infections was 2848 cases per 100,000 population in 2007 (Medscape)

Duration of Infectiousness and disease

Symptomology

Range from mild diarrhea to severe dysentery with frequent passage of bloody, mucoid, small-volume stools. May cause destruction of colon epithelium resulting in acute colitis.

Latency

Asymptomatic Rates

Excretion Rates (see Exposure)

An infected person excretes the organisms in the stool and this can extend up to 4 weeks from the onset of illness.

Immunity

Currently, no vaccine exists to prevent Shigellosis. However, individuals who have already been infected are generally immune to further infection by the same species. Broad spectrum antibiotic resistance is becoming increasingly prevalent, especially in antimicrobial drug sulfonamides, decycline, chloramphenicol, and ampicillin.

A genus of Gram-negative, nonspore forming, non-motile, rod-shaped bacteria (Wikipedia)

Shigella: Dose Response Models
Beta-Poisson, α is 0.27, N₅₀ is 1.48E+03

References

Wikipedia Page
Medscape Page
CDC Shigellosis Page
Recent Works on Microbes and Infections in China