Typhoid and paratyphoid fevers are systemic diseases caused by the bacteria Salmonella typhi and Salmonella paratyphi, respectively. Humans are the only reservoir for Salmonella typhi (which is the most serious), whereas Salmonella paratyphi also has animal reservoirs. Humans can carry the bacteria in the gut for very long times (chronic carriers), and transmit the bacteria to other persons (either directly or via food or water contamination).
After 1-2 weeks incubation period, a disease characterised by high fever, malaise, cough, rash and enlarged spleen develops. Diarrhoea may be present at some stage. When Salmonella typhi is the cause, intestinal perforation and haemorrhage may occur. Salmonella typhi blood stream infection can also cause infection in all organs. Antibiotic therapy has radically changed the prognosis of typhoid, which, untreated, has a 10% death rate. Preventive measures include good personal and food hygiene. An effective vaccine is also available.