Typhoid fever, also known simply as typhoid, is a 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.
Typhoid is caused by the bacterium Salmonella enterica subsp. enterica serovar Typhi growing in the , Peyer's 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 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 Widal test. 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 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. The disease is most common in India. 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".
In this test, the serum is mixed with a dead bacterial suspension of Salmonella with specific antigens. If the patient's serum contains antibodies against those antigens, they get attached to them, forming clumps. If clumping does not occur, the test is negative. The Widal test is time-consuming and prone to significant false positives. It may also be falsely negative in recently infected people. But unlike the Typhidot test, the Widal test quantifies the specimen with titer.
The sample pad of this kit contains colloidal gold-anti-human IgG or gold-anti-human IgM. If the sample contains IgG and IgM antibodies against those antigens, they will react and turn red. The typhidot test becomes positive within 2–3 days of infection.
Two colored bands indicate a positive test. A single control band indicates a negative test. A single first fixed line or no band at all indicates an invalid test. Typhidot's biggest limitation is that it is not quantitative, just positive or negative.
If the serum does not have an antibody in it, the blue particles attach to the brown particles and settle at the bottom, producing a colorless solution, which means the test is negative.
Since the 1990s, the WHO has recommended two typhoid fever vaccines. The ViPS vaccine is given by injection and the Ty21a by capsules. Only people over age two are recommended to be vaccinated with the ViPS vaccine, and it requires a revaccination after 2–3 years, with a 55–72% efficacy. The Ty21a vaccine is recommended for people five and older, lasting 5–7 years with 51–67% efficacy. The two vaccines have proved safe and effective for epidemic disease control in multiple regions.
A version of the vaccine combined with a hepatitis A vaccine is also available.
Results of a phase 3 trial of typhoid conjugate vaccine (TCV) in December 2019 reported 81% fewer cases among children.
Properly treated, typhoid fever is not fatal in most cases. Antibiotics such as ampicillin, chloramphenicol, trimethoprim-sulfamethoxazole, amoxicillin, and ciprofloxacin have been commonly used to treat it.Baron S et al. Treatment with antibiotics reduces the case-fatality rate to about 1%.
Without treatment, some patients develop sustained fever, bradycardia, hepatosplenomegaly, abdominal symptoms, and occasionally pneumonia. In white-skinned patients, pink spots, which fade on pressure, appear on the skin of the trunk in up to 20% of cases. In the third week, untreated cases may develop gastrointestinal and cerebral complications, which may prove fatal in 10–20% of cases. The highest case fatality rates are reported in children under 4. Around 2–5% of those who contract typhoid fever become chronic carriers, as bacteria persist in the biliary tract after symptoms have resolved.
For surgical treatment, most surgeons prefer simple closure of the perforation with drainage of the peritoneum. Small bowel resection is indicated for patients with multiple perforations. If antibiotic treatment fails to eradicate the hepatobiliary carriage, the gallbladder should be resected. Cholecystectomy is sometimes successful, especially in patients with , but is not always successful in eradicating the carrier state because of persisting hepatic infection.
Ciprofloxacin resistance is an increasing problem, especially in the Indian subcontinent and Southeast Asia. Many centres are shifting from ciprofloxacin to ceftriaxone as the first line for treating suspected typhoid originating in South America, India, Pakistan, Bangladesh, Thailand, or Vietnam. Also, it has been suggested that azithromycin is better at treating resistant typhoid than both fluoroquinolone drugs and ceftriaxone. Azithromycin can be taken by mouth and is less expensive than ceftriaxone, which is given by injection.
A separate problem exists with laboratory testing for reduced susceptibility to ciprofloxacin; current recommendations are that isolates should be tested simultaneously against ciprofloxacin (CIP) and against nalidixic acid (NAL), that isolates sensitive to both CIP and NAL should be reported as "sensitive to ciprofloxacin", and that isolates sensitive to CIP but not to NAL should be reported as "reduced sensitivity to ciprofloxacin". But an analysis of 271 isolates found that around 18% of isolates with reduced susceptibility to fluoroquinolones, the class to which CIP belongs (MIC 0.125–1.0 mg/L), would not be detected by this method.
Before the antibiotic era, the case fatality rate of typhoid fever was 10–20%. Today, with prompt treatment, it is less than 1%,Heymann, David L., ed. (2008), Control of Communicable Diseases Manual, Washington, D.C.: American Public Health Association, pg 665. . 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. Third world nations have the highest rates. People in these areas often lack access to clean water, proper sanitation systems, and proper healthcare 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. Since November 2016, Pakistan has had an outbreak of extensively drug-resistant (XDR) typhoid fever.
In Europe, a report based on data for 2017 retrieved from The European Surveillance System (TESSy) on the distribution of confirmed typhoid and paratyphoid fever cases found that 22 EU/EEA countries reported a total of 1,098 cases, 90.9% of which were travel-related, mainly acquired during travel to South Asia.
In 1847, William Budd learned of an epidemic of typhoid fever in Clifton, and identified that all 13 of 34 residents who had contracted the disease drew their drinking water from the same well. Notably, this observation was two years before John Snow first published an early version of his theory that contaminated water was the central conduit for transmitting cholera. Budd later became health officer of Bristol ensured a clean water supply, and documented further evidence of typhoid as a water-borne illness throughout his career.
In April 1880, three months before Eberth's publication, Edwin Klebs described short and Filamentation bacilli in the Peyer's patches in typhoid victims. The bacterium's role in disease was speculated but not confirmed.
In 1880, Karl Joseph Eberth described a bacillus that he suspected was the cause of typhoid.
Eberth's findings were verified by Robert Koch Eberth is given credit for discovering the bacterium definitively by successfully isolating the same bacterium from 18 of 40 typhoid victims and failing to discover the bacterium present in any "control" victims of other diseases. In 1884, pathologist Georg Theodor August Gaffky (1850–1918) confirmed Eberth's findings. Gaffky isolated the same bacterium as Eberth from the spleen of a typhoid victim, and was able to grow the bacterium on solid media. The organism was given names such as Eberth's bacillus, Eberthella Typhi, and Gaffky-Eberth bacillus. Today, the bacillus that causes typhoid fever goes by the scientific name Salmonella enterica serovar Typhi.
Outbreaks in traveling military groups led to the creation of the Lyster bag in 1915: a bag with a faucet that can be hung from a tree or pole, filled with water, and comes with a chlorination tablet to drop into the water. The Lyster bag was essential for the survival of American soldiers in the Vietnam War.
The most notorious carrier of typhoid fever, but by no means the most destructive, was Mary Mallon, known as Typhoid Mary. Although other cases of human-to-human spread of typhoid were known at the time, the concept of an asymptomatic carrier, who was able to transmit disease, had only been hypothesized and not yet identified or proven. Mary Mallon became the first known example of an asymptomatic carrier of an infectious disease, making typhoid fever the first known disease being transmissible through asymptomatic hosts. The cases and deaths caused by Mallon were mainly upper-class families in New York City. At the time of Mallon's tenure as a personal cook for upper-class families, New York City reported 3,000 to 4,500 cases of typhoid fever annually. In the summer of 1906, two daughters of a wealthy family and maids working in their home became ill with typhoid fever. After investigating their home water sources and ruling out water contamination, the family hired civil engineer George Soper to conduct an investigation of the possible source of typhoid fever in the home. Soper described himself as an "epidemic fighter". His investigation ruled out many sources of food, and led him to question if the cook the family hired just prior to their household outbreak, Mallon, was the source. Since she had already left and begun employment elsewhere, he proceeded to track her down in order to obtain a stool sample. When he was able to finally meet Mallon in person he described her by saying "Mary had a good figure and might have been called athletic had she not been a little too heavy." In recounts of Soper's pursuit of Mallon, his only remorse appears to be that he was not given enough credit for his relentless pursuit and publication of her personal identifying information, stating that the media "robs me of whatever credit belongs to the discovery of the first typhoid fever carrier to be found in America." Ultimately, 51 cases and 3 deaths were suspected to be caused by Mallon.
In 1924, the city of Portland, Oregon, experienced an outbreak of typhoid fever, consisting of 26 cases and 5 deaths, all deaths due to intestinal hemorrhage. All cases were concluded to be due to a single milk farm worker, who was shedding large amounts of the typhoid pathogen in his urine. Misidentification of the disease, due to inaccurate Widal test results, delayed identification of the carrier and proper treatment. Ultimately, it took four samplings of different secretions from all of the dairy workers in order to successfully identify the carrier. Upon discovery, the dairy worker was forcibly quarantined for seven weeks, and regular samples were taken, most of the time the stool samples yielding no typhoid and often the urine yielding the pathogen. The carrier was reported as being 72 years old and appearing in excellent health with no symptoms. Pharmaceutical treatment decreased the amount of bacteria secreted, however, the infection was never fully cleared from the urine, and the carrier was released "under orders never again to engage in the handling of foods for human consumption." At the time of release, the authors noted "for more than fifty years he has earned his living chiefly by milking cows and knows little of other forms of labor, it must be expected that the closest surveillance will be necessary to make certain that he does not again engage in this occupation."
Overall, in the early 20th century the medical profession began to identify disease carriers and evidence of transmission independent of water contamination. In a 1933 American Medical Association publication, physicians' treatment of asymptomatic carriers is best summarized by the opening line "Carriers of typhoid bacilli are a menace". Within the same publication, the first official estimate of typhoid carriers is given: 2–5% of all typhoid patients, and distinguished between temporary carriers and chronic carriers. The authors further estimate that there are four to five chronic female carriers to every one male carrier, although offered no data to explain this assertion of a gender difference in the rate of typhoid carriers. As far as treatment, the authors suggest: "When recognized, carriers must be instructed as to the disposal of excreta as well as to the importance of personal cleanliness. They should be forbidden to handle food or drink intended for others, and their movements and whereabouts must be reported to the public health officers".
Today, typhoid carriers exist all over the world, but the highest incidence of asymptomatic infection is likely to occur in South/Southeast Asian and Sub-Saharan countries. The Los Angeles County department of public health tracks typhoid carriers and reports the number of carriers identified within the county yearly; between 2006 and 2016 0–4 new cases of typhoid carriers were identified per year. Cases of typhoid fever must be reported within one working day from identification. As of 2018, chronic typhoid carriers must sign a "Carrier Agreement" and are required to test for typhoid shedding twice yearly, ideally every 6 months. Carriers may be released from their agreements upon fulfilling "release" requirements, based on completion of a personalized treatment plan designed with medical professionals. Fecal or gallbladder carrier release requirements: 6 consecutive negative feces and urine specimens submitted at 1-month or greater intervals beginning at least 7 days after completion of therapy. Urinary or kidney carrier release requirements: 6 consecutive negative urine specimens submitted at 1-month or greater intervals beginning at least 7 days after completion of therapy.
Due to the nature of asymptomatic cases, many questions remain about how individuals can tolerate infection for long periods, how to identify such cases, and efficient options for treatment. Researchers are working to understand asymptomatic infection with Salmonella species by studying infections in laboratory animals, which will ultimately lead to improved prevention and treatment options for typhoid carriers. In 2002, John Gunn described the ability of Salmonella sp. to form on in mice, providing a model for studying carriage in the gallbladder. Denise Monack and Stanley Falkow described a mouse model of asymptomatic intestinal and systemic infection in 2004, and Denise monack went on to demonstrate that a subpopulation of superspreaders are responsible for the majority of transmission to new hosts, following the Pareto principle of disease transmission, and that the intestinal microbiota likely plays a role in transmission. Denise monack's mouse model allows long-term carriage of Salmonella in mesenteric lymph nodes, spleen and liver.
Citing the example of the Second Boer War, during which many soldiers died from easily preventable diseases, Wright convinced the British Army that 10 million vaccine doses should be produced for the troops being sent to the Western Front, thereby saving up to half a million lives during World War I. The British Army was the only combatant at the outbreak of the war to have its troops fully immunized against the bacterium. For the first time, their casualties due to combat exceeded those from disease.
In 1909, Frederick F. Russell, a U.S. Army physician, adopted Wright's typhoid vaccine for use with the Army, and two years later, his vaccination program became the first in which an entire army was immunized. It eliminated typhoid as a significant cause of morbidity and mortality in the U.S. military. Typhoid vaccination for members of the American military became mandatory in 1911. Before the vaccine, the rate of typhoid fever in the military was 14,000 or greater per 100,000 soldiers. By World War I, the rate of typhoid in American soldiers was 37 per 100,000.
During the Second World War, the United States Army authorized the use of a trivalent vaccine – containing heat-inactivated Typhoid, Paratyphi A and Paratyphi B pathogens.
In 1934, the discovery of the Vi capsular antigen by Arthur Felix and Miss S. R. Margaret Pitt enabled the development of the safer Vi Antigen vaccine – which is widely in use today. Arthur Felix and Margaret Pitt also isolated the strain Ty2, which became the parent strain of Ty21a, the strain used as a live-attenuated vaccine for typhoid fever today.
Signs and symptoms
Causes
Bacteria
Transmission
Diagnosis
Widal test
Rapid diagnostic tests
Typhidot
Tubex test
Prevention
Vaccination
Treatment
Oral rehydration therapy
Antibiotics
Surgery
Resistance
Epidemiology
Outbreaks
History
Early descriptions
Definition and evidence of transmission
Cause
Chlorination of water
Direct transmission and carriers
Vaccine development
Antibiotics and resistance
Terminology
Society and culture
Notable people
Further reading
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