Typhoid fever is a bacterial infection caused by Salmonella typhi that can spread throughout the body and affect many organs if not promptly treated. It causes symptoms like weakness, stomach pain, headache, diarrhea or constipation, cough, and loss of appetite that generally start 10-14 days after exposure. Typhoid fever requires treatment with antibiotics for 7-14 days, though more severe cases may need to be treated in the hospital with antibiotic injections.