• The incubation period of paratyphoid infections is 6–30 days.
• The onset of illness is insidious, with gradually increasing fatigue and a fever that increases daily from low-grade to as high as 102°F–104°F (38°C–40°C) by the third to fourth day of illness.
• Headache, malaise, and anorexia are nearly universal.
• A transient, macular rash of rose-colored spots can occasionally be seen on the trunk.
• Fever is commonly lowest in the morning, reaching a peak in late afternoon or evening. Untreated, the disease can last for a month.

Infection is characterized by a sustained fever, headache, abdominal pain, malaise, anorexia, a non productive cough (in early stage of illness), a relative Bradycardia (slow heart rate), and Hepatosplenomegaly (an enlargement of the liver or spleen). Approximately 30% of Caucasians will develop rosy spots on the central body. In adults, constipation is more common than diarrhea.

Only 20% to 40% of people will initially have abdominal pain. Nonspecific symptoms such as chills, diaphoresis (perspiration), headache, anorexia, cough, weakness, sore throat, dizziness, and muscle pains are frequently present before the onset of fever. Some very rare symptoms are psychosis (mental disorder), confusion and seizures.