Typhoid fever is caused by Salmonella typhi bacteria and results from ingestion of contaminated food or water. It is diagnosed by detecting the bacteria in stool culture. Symptoms include fever, headache, abdominal pain and lethargy. It is treated with antibiotics which can reduce mortality to 1-2%. Approximately 3-5% of patients become long-term carriers after recovery. Carriers can contaminate food and water supplies, spreading the disease.