Salmonella are Gram-negative bacteria of the Enterobacteriaceae family. Salmonella are divided into two main groups on the basis of the illness they cause – typhoidal and non-typhoidal Salmonella. Nontyphoidal Salmonella usually cause self-limiting gastrointestinal disease including diarrhoea and abdominal cramps. Persons with weak immune systems, such as those with advanced HIV/AIDS, may experience more severe disease. Occasionally Salmonella organisms invade beyond the gut and cause disseminated disease or infections such as meningitis or liver abscesses. Disease of any kind due to non-typhoidal salmonella is called ‘salmonellosis’. Typhoidal Salmonella cause a distinct disease called typhoid fever, a potentially life-threatening febrile, systemic illness, which is discussed in a separate FAQ document.