53: Typhoid Fever

Classification: ICD-9 002.0; ICD-10 A01

Syndromes and synonyms: Enteric fever, typhus abdominalis.

Agent: Salmonella enterica enterica serovar Typhi (S. Typhi), a Gram-negative bacillus. S. Typhi belongs to Salmonella serogroup D and possesses somatic antigen O9, a single flagellar antigen Hd, and virulence antigen Vi. S. Paratyphi A can cause similar disease.

Reservoir: Mainly humans; rarely domestic animals. Humans can be short-term carriers after an infection (10%) or become chronic carriers in the biliary tract (1–5%), shedding viable bacteria in the stool. Chronic carriers are mainly adults with pre-existing biliary tract pathology. Urinary carriage may occur in areas where Schistosoma haematobium is endemic.

Vector: Flies can contaminate foods.

Transmission: Via fecal contaminated water, drinks or food from infected individuals or carriers; transmission may also occur in men who have sex with men.

Cycle: Infected individuals shed bacteria into environment, contaminating water and food products that are subsequently ingested by other humans.

Incubation period

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