Nontyphoidal Salmonella organisms cause asymptomatic gastrointestinal tract carriage, gastroenteritis, bacteremia, and focal infections (such as meningitis and osteomyelitis). These disease categories are not mutually exclusive but represent a spectrum of illness. The most common illness associated with nontyphoidal Salmonella infection is gastroenteritis, in which diarrhea, abdominal cramps, and fever are common manifestations. The site of infection usually is the distal small intestine as well as the colon. Sustained or intermittent bacteremia can occur, and focal infections are recognized in as many as 10% of patients with Salmonella bacteremia.

Salmonella serotype Typhi and several other Salmonella serotypes can cause a protracted bacteremic illness often referred to as enteric or typhoid fever. The onset of illness typically is gradual, with manifestations such as fever, constitutional symptoms (eg, headache, malaise, anorexia, and lethargy), abdominal pain and tenderness, hepatomegaly, splenomegaly, rose spots, and change in mental status. Enteric fever can manifest as a mild, nondescript febrile illness in young children, in whom sustained or intermittent bacteremia can occur. Constipation can be an early feature. Diarrhea commonly occurs in children.