Typhoid fever, also known as typhoid, is a disease caused by Salmonella serotype Typhi bacteria. Symptoms vary from mild to severe, and usually begin six to 30 days after exposure. Often there is a gradual onset of a high fever over several days. This is commonly accompanied by weakness, abdominal pain, constipation, headaches, and mild vomiting. Some people develop a skin rash with rose colored spots. In severe cases, people may experience confusion. Without treatment, symptoms may last weeks or months. Diarrhea may be severe, but is uncommon. Other people may carry the bacterium without being affected, but they are still able to spread the disease. Typhoid fever is a type of enteric fever, along with paratyphoid fever. S. enterica Typhi is believed to infect and replicate only within humans.Typhoid is caused by the bacterium Salmonella enterica subsp. enterica serovar Typhi growing in the intestines, peyers patches, mesenteric lymph nodes, spleen, liver, gallbladder, bone marrow and blood. Typhoid is spread by eating or drinking food or water contaminated with the feces of an infected person. Risk factors include limited access to clean drinking water and poor sanitation. Those who have not yet been exposed to the pathogen and ingest contaminated drinking water or food are most at risk for developing symptoms. Only humans can be infected; there are no known animal reservoirs.Diagnosis is by culturing and identifying S. enterica Typhi from patient samples or detecting an immune response to the pathogen from blood samples.
In the U.S., about 400 cases occur each year, 75% of which are acquired while traveling internationally.Before the antibiotic era, the case fatality rate of typhoid fever was 10%–20%. Today, with prompt treatment, it is less than 1%, but 3%–5% of people who are infected develop a chronic infection in the gall bladder. Since S. enterica subsp. enterica serovar Typhi is human-restricted, these chronic carriers become the crucial reservoir, which can persist for decades for further spread of the disease, further complicating its identification and treatment. Lately, the study of S. enterica subsp. enterica serovar Typhi associated with a large outbreak and a carrier at the genome level provides new insight into the pathogenesis of the pathogen.In industrialized nations, water sanitation and food handling improvements have reduced the number of typhoid cases. Developing nations, such as those in parts of Asia and Africa, have the highest rates. These areas lack access to clean water, proper sanitation systems, and proper health-care facilities. In these areas, such access to basic public-health needs is not expected in the near future.In 2004–2005 an outbreak in the Democratic Republic of Congo resulted in more than 42,000 cases and 214 deaths.