Typhoid and paratyphoid (enteric) fevers Typhoid and paratyphoid fevers, which are transmitted by the faecal-oral route, are impoant causes of fever in the Indian subcontinent, sub-Saharan Africa and Latin America. Elsewhere, they are relatively rare. Enteric fevers are caused by infection with Salmonella Typhi and Salmonella Paratyphi A and B. After a few days of bacteraemia, the bacilli localise, mainly in the lymphoid tissue of the small intestine, resulting in typical lesions in the Peyer's patches and follicles. These swell at first, then ulcerate and usually heal. After clinical recovery, about 5% of patients become chronic carriers (i.e. continue to excrete the bacteria after 1 year); the bacilli may live in the gallbladder for months or years and pass intermittently in the stool and, less commonly, in the urine. Clinical features Typhoid fever The incubation period is typically about 10-14 days but can be longer, and the onset may be insidious. The temperature rises in a stepladder fashion for 4 or 5 days with malaise, increasing headache, drowsiness and aching in the limbs. Constipation may be caused by swelling of lymphoid tissue around the ileocaecal junction, although in children diarrhoea and vomiting may be prominent early in the illness. The pulse is often slower than would be expected from the height of the temperature, i.e. a relative bradycardia. At the end of the first week, a rash may appear on the upper abdomen and on the back as sparse, slightly raised, rose-red spots, which fade on pressure. It is usually visible only on white skin. Cough and epistaxis occur. Around the 7th-10thday, the spleen becomes palpable. Constipation is followed by diarrhoea and abdominal distension with tenderness. Bronchitis and delirium may develop. If untreated, by the end of the second week the patient may be profoundly ill. Salmonella enterica is a facultative anaerobe and is a gram negative, motile ... For enteric fever, the infectious dose is about 105 bacilli by ingestion Ref Harrison20th edition pg 1079