Typhoid fever, also known as typhoid, is an orally contracted disease caused by Salmonella enterica serotype Typhi bacteria, also called Salmonella Typhi. 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 it without being affected, but are still contagious. Typhoid fever is a type of enteric fever, along with paratyphoid fever. Salmonella 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, Peyer's patches, mesenteric lymph nodes, spleen, liver, gallbladder, bone marrow and blood. Typhoid is spread by ingesting 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 it 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. Salmonella typhi which causes typhoid fever is different from the other Salmonella bacteria that usually cause salmonellosis, a common type of food poisoning. Diagnosis is performed by culturing and identifying S. typhi from patient samples or detecting an immune response to the pathogen from blood samples. Recently, new advances in large-scale data collection and analysis have allowed researchers to develop better diagnostics, such as detecting changing abundances of small molecules in the blood that may specifically indicate typhoid fever. Diagnostic tools in regions where typhoid is most prevalent are quite limited in their accuracy and specificity, and the time required for a proper diagnosis, the increasing spread of antibiotic resistance, and the cost of testing are also hardships for under-resourced healthcare systems. A typhoid vaccine can prevent about 40–90% of cases during the first two years. The vaccine may have some effect for up to seven years. For those at high risk or people traveling to areas where it is common, vaccination is recommended. Other efforts to prevent it include providing clean drinking water, good sanitation, and handwashing. Until an infection is confirmed as cleared, the infected person should not prepare food for others. Typhoid is treated with antibiotics such as azithromycin, fluoroquinolones, or third-generation cephalosporins. Resistance to these antibiotics has been developing, which has made treatment more difficult. In 2015, 12.5 million new typhoid cases were reported. Children are most commonly affected. Typhoid decreased in the developed world in the 1940s as a result of improved sanitation and the use of antibiotics. Every year about 400 cases are reported in the U.S. and an estimated 6,000 people have typhoid. In 2015, it resulted in about 149,000 deaths worldwide – down from 181,000 in 1990. Without treatment, the risk of death may be as high as 20%. With treatment, it is between 1% and 4%. Typhus is a different disease, caused by unrelated species of bacteria. Owing to their similar symptoms, they were not recognized as distinct diseases until the 1800s. "Typhoid" means "resembling typhus".
Signs and symptoms Classically, the progression of untreated typhoid fever has three distinct stages, each lasting about a week. Over the course of these stages, the patient becomes exhausted and emaciated.
In the first week, the body temperature rises slowly, and fever fluctuations are seen with relative bradycardia (Faget sign), malaise, headache, and cough. A bloody nose (epistaxis) is seen in a quarter of cases, and abdominal pain is also possible. A decrease in the number of circulating white blood cells (leukopenia) occurs with eosinopenia and relative lymphocytosis; blood cultures are positive for S. enterica subsp. enterica serovar Typhi. The Widal test is usually negative. In the second week, the person is often too tired to get up, with high fever in plateau around 39–40.5 °C (102.2–104.9 °F) and bradycardia (sphygmothermic dissociation or Faget sign), classically with a dicrotic pulse wave. Delirium can occur, where the patient is often calm, but sometimes becomes agitated. This delirium has given typhoid the nickname "nervous fever". Rose spots appear on the lower chest and abdomen in around a third of patients. Rhonchi (rattling breathing sounds) are heard in the base of the lungs. The abdomen is distended and painful in the right lower quadrant, where a rumbling sound can be heard. Diarrhea can occur in this stage, but constipation is also common. The spleen and liver are enlarged (hepatosplenomegaly) and tender, and liver transaminases are elevated. The Widal test is strongly positive, with antiO and antiH antibodies. Blood cultures are sometimes still positive. In the third week of typhoid fever, possible complications include: The fever is still very high and oscillates very little over 24 hours. Dehydration ensues along with malnutrition, and the patient is delirious. A third of affected people develop a macular rash on the trunk. Intestinal haemorrhage due to bleeding in congested Peyer's patches occurs; this can be very serious but is usually not fatal. Intestinal perforation in the distal ileum is a critical complication and often fatal. It may occur without alarming symptoms until sepsis or diffuse peritonitis sets in. Respiratory diseases such as pneumonia and acute bronchitis Encephalitis Neuropsychiatric symptoms (described as "muttering delirium" or "coma vigil"), with picking at bedclothes or imaginary objects. Metastatic abscesses, cholecystitis, endocarditis, and osteitis. Low platelet count (thrombocytopenia) is sometimes seen.
Causes
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