However, when these strains do cause disease in humans, it is often invasive and can be life-threatening. Group 3 includes the remaining strains. Typically, such strains cause gastroenteritis which is often mild and self-limiting but can be severe in the young, the elderly, and patients with weakened resistance against infectious diseases. The clinical course of human salmonellosis is usually characterized by acute onset of fever, abdominal pain, diarrhoea, nausea and sometimes vomiting. In some cases, particularly in the very young and in the elderly, dehydration can become severe and life threatening.
Serious complications occur in a small proportion of cases.
The United Kingdom Food and Drink Federation calculated in its 1994 report that foodborne illness, principally salmonellosis, is costing the British economy about UK 1,000 million annually. 104 initially emerged in cattle in 1988 in England and Wales. Subsequently, the strain has been isolated from poultry, sheep, pigs, and horses. Antimicrobial therapy is used extensively to combat Salmonella typhimurium infection in animals. The evolution of a strain resistant to the commonly-used antibiotics has made infections with Salmonella typhimurium in food animals difficult to control and it will likely remain an animal health problem for quite some time.