Typhoid fever is a bacterial disease, caused by Salmonella typhi. It is transmitted through the ingestion of food or drink contaminated by the faeces or urine of infected people.
Symptoms usually develop 1–3 weeks after exposure, and may be mild or severe. They include high fever, malaise, headache, constipation or diarrhoea, rose-coloured spots on the chest, and enlarged spleen and liver. Healthy carrier state may follow acute illness.
Typhoid fever can be treated with antibiotics. However, resistance to common antimicrobials is widespread. Healthy carriers should be excluded from handling food.
Typhoid Fever Vaccines
Two new-generation two typhoid vaccines of demonstrated safety and efficacy are available on the international market, the Vi polysaccharide vaccine which is administrated by injection and the live attenuated Ty21a vaccine which is given orally. The Vi polysaccharide vaccine is composed of purified Vi capsular polysaccharide from the Ty2 S. Typhi strain. It is administered subcutaneously or intramuscularly. The Ty21a oral vaccine is based on an attenuated Ty2 strain in which multiple genes, including the genes responsible for the production of the Vi polysaccharide, have been mutated. The oral Ty21a vaccine is available as enteric-coated capsules or a liquid suspension. The whole-cell heat-phenol or acetone inactivated vaccine is still available in several developing countries. However, given its relatively high reactogenicity, this vaccine should be replaced by the Vi polysaccharide vaccine or the Ty21a vaccine.