Typhoid fever | |
---|---|
Other names | Enteric fever, slow fever |
Causative agent: Salmonella enterica serological variant Typhi (shown under a microscope with flagellar stain) | |
Specialty | Infectious diseases |
Symptoms | Fever that starts low and increases daily, possibly reaching as high as 104.9 °F (40.5 °C) Headache, weakness and fatigue, muscle aches, sweating, dry cough, loss of appetite, weight loss, stomach pain, diarrhea or constipation, rash, swollen stomach (enlarged liver or spleen) |
Usual onset | 1–2 weeks after ingestion |
Duration | Usually 7–10 days after antibiotic treatment begins. Longer if there are complications or drug resistance. |
Causes | Gastrointestinal infection of Salmonella enterica serotype Typhi |
Risk factors | Living in or travel to areas where typhoid fever is established; work as a clinical microbiologist handling Salmonella Typhi bacteria; have close contact with someone who is infected or has recently been infected with typhoid fever; drink water polluted by sewage that contains Salmonella Typhi |
Prevention | Preventable by vaccine. Travelers to regions with higher typhoid prevalence are usually encouraged to get a vaccination before travel. |
Treatment | Antibiotics, hydration, surgery in extreme cases. Quarantine to avoid exposing others (not commonly done in modern times). |
Prognosis | Likely to recover without complications if proper antibiotics administered and diagnosed early. If infecting strain is multi-drug resistant or extensively drug resistant then prognosis more difficult to determine.
Among untreated acute cases, 10% will shed bacteria for three months after initial onset of symptoms, and 2–5% will become chronic typhoid carriers.[1] Some carriers are diagnosed by positive tissue specimen. Chronic carriers are by definition asymptomatic.[1] |
Typhoid fever, also known simply as typhoid, is a disease caused by Salmonella enterica serotype Typhi bacteria, also called Salmonella typhi.[2][3] Symptoms vary from mild to severe, and usually begin six to 30 days after exposure.[4][5] Often there is a gradual onset of a high fever over several days.[4] This is commonly accompanied by weakness, abdominal pain, constipation, headaches, and mild vomiting.[6][5][7] Some people develop a skin rash with rose colored spots.[5] In severe cases, people may experience confusion.[7] Without treatment, symptoms may last weeks or months.[5] Diarrhea may be severe, but is uncommon.[7] Other people may carry it without being affected, but are still contagious.[8] Typhoid fever is a type of enteric fever, along with paratyphoid fever.[2] Salmonella enterica Typhi is believed to infect and replicate only within humans.[9]
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.[5][7] Typhoid is spread by eating or drinking food or water contaminated with the feces of an infected person.[8] Risk factors include limited access to clean drinking water and poor sanitation.[2] Those who have not yet been exposed to it and ingest contaminated drinking water or food are most at risk for developing symptoms.[7] Only humans can be infected; there are no known animal reservoirs.[8] Salmonella Typhi which causes typhoid fever is different than the other Salmonella bacteria that usually cause salmonellosis, a common type of food poisoning.[10]
Diagnosis is performed by culturing and identifying S. enterica typhi from patient samples or detecting an immune response to the pathogen from blood samples.[5][2][11] 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.[12] 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.[9]
A typhoid vaccine can prevent about 40–90% of cases during the first two years.[13] The vaccine may have some effect for up to seven years.[2] For those at high risk or people traveling to areas where it is common, vaccination is recommended.[8] Other efforts to prevent it include providing clean drinking water, good sanitation, and handwashing.[5][8] Until an infection is confirmed as cleared, the infected person should not prepare food for others.[5] Typhoid is treated with antibiotics such as azithromycin, fluoroquinolones, or third-generation cephalosporins.[2] Resistance to these antibiotics has been developing, which has made treatment more difficult.[2][14][15]
In 2015, 12.5 million new typhoid cases were reported.[16] The disease is most common in India.[2] Children are most commonly affected.[2][8] Typhoid decreased in the developed world in the 1940s as a result of improved sanitation and the use of antibiotics.[8] Every year about 400 cases are reported in the U.S. and an estimated 6,000 people have typhoid.[7][17] In 2015, it resulted in about 149,000 deaths worldwide – down from 181,000 in 1990.[18][19] Without treatment, the risk of death may be as high as 20%.[8] With treatment, it is between 1% and 4%.[2][8]
Typhus is a different disease, caused by unrelated species of bacteria.[20] Owing to their similar symptoms, they were not recognized as distinct diseases until the 1800s. "Typhoid" means "resembling typhus".[21]