Infection with the bacterium. There are various types: paratyphoid A, B and C and the other Infection with these bacteria can result in various clinical pictures. Initially the infection can seem much like typhoid, with symptoms in organs other than the bowels. This is particularly so with paratyphoid B, but it occurs rarely. There is a form confined to the intestines, with symptoms akin to gastroenteritis, sometimes caused by paratyphoid B or C, but more often by other salmonellae. There is a short incubation period of 8 to 48 hours, followed by sudden nausea, vomiting, colic, fever and diarrhoea, sometimes with blood and mucus. Usually the bacteria are carried in contaminated food (such as pork, poultry and salads). The patient usually recovers spontaneously in 2 to 5 days; young children may suffer from dehydration. The bacteria remain in some patients, who are designated carriers if there are still bacteria in the faeces after 6 months. Carriers can contaminate large quantities of food, particularly if they are kitchen workers, for example. Diagnosis is by faeces culture. In mild cases no special measures are necessary because the illness clears up spontaneously. Treatment is as in all forms of gastroenteritis: no solid food, plenty of liquid (tea, broth) and possibly anti-diarrhoea drugs. Antibiotics are generally of no use.