Typhoid fever is caused by the Salmonella typhi bacteria. It is transmitted through the fecal-oral route via contaminated food or water or direct contact. After incubation, the bacteria multiply in the intestines and spread to the liver, spleen and gallbladder causing systemic infection. Common symptoms include fever, abdominal pain and diarrhea. Diagnosis is through blood or stool culture. Treatment involves antibiotics like quinolones or cephalosporins. Prevention focuses on proper hygiene, food handling and water treatment. Typhoid fever is a major public health problem in developing countries.