What are the causes?
Typhoid and paratyphoid fever are caused by bacteria from the genus Salmonella. Humans are the only reservoir for the bacteria, which belong to the serotype Typhi, or less often to the serotypes Paratyphi A, B or C. Infection is usually caused by the ingestion of water or food contaminated with human feces or by direct person-to-person transmission.
What are the symptoms?
One to three weeks after infection, patients begin to suffer from constant fever, headache, anorexia, weakness and abdominal pain with diarrhea or constipation, and sometimes a skin rash.
In mild forms, the symptoms stay the same for around two weeks, and convalescence lasts for several weeks. In more severe forms, patients may experience complications in the gut, heart or brain. Typhoid fever can be fatal if left untreated.
The mortality rate is 10% in the absence of effective antibiotic treatment, compared with less than 1% for other forms of Salmonella infection.
How are typhoid and paratyphoid fever diagnosed?
Diagnosis is generally confirmed by blood, bone marrow or stool culture to isolate the bacteria responsible for the disease.
What treatments are available?
Appropriate antibiotic therapy reduces the mortality risk to less than 1%. Fluoroquinolones (ciprofloxacin), third-generation cephalosporins or azithromycin are the antibiotics most commonly used to treat typhoid and paratyphoid fever. However, more and more antibiotic-resistant strains are being isolated, particularly in South-East Asia and the Indian subcontinent. Over 90% of strains isolated in these regions have reduced susceptibility to fluoroquinolones.(1) Since 2018, strains resistant to both ciprofloxacin and third-generation cephalosporins have been isolated in mainland France.(1) More recently, strains resistant to azithromycin have emerged. All these strains originating from South Asia are being closely monitored by the CNR.
How can typhoid and paratyphoid fever be prevented?
Prevention is based on epidemiological surveillance and efforts to eliminate fecal contamination. The spread of Salmonella bacteria can be prevented by ensuring widespread availability of clean, bacteriologically safe water, effective wastewater treatment, generalized sewage services, controls in shellfish harvesting areas, pasteurization of food (especially butter and milk) and strict compliance with hygiene regulations for all restaurant industry workers.
Typhoid vaccines administered by injection (single-dose) or orally (three doses) may be recommended for travelers. The vaccine lasts for approximately three years and provides around 60% protection in endemic areas. Vaccination should however go hand in hand with essential hygiene measures regarding water, food and hand washing.
Who is affected?
Typhoid and paratyphoid fever are caused by Salmonella serotypes that are specifically adapted to humans, the most common of which is Typhi, followed in descending order of prevalence by Paratyphi A, some strains of Paratyphi B, and Paratyphi C. Infection occurs through the ingestion of water or food contaminated with human feces. Like all fecal-orally transmitted diseases, these fevers occur most often in areas with low standards of hygiene, especially in developing countries in Asia, Africa or Latin America.
How many people are affected?
The most recent data suggests that there are more than 14.3 million cases of typhoid and paratyphoid fever worldwide each year, resulting in more than 135,000 deaths (compared with more than 20 million cases and 230,000 deaths in 1990).(2)
Although currently much less prevalent, the disease is still present in industrialized countries.
In France, typhoid and paratyphoid fever have been notifiable diseases that must be reported to the health authorities since 1903 (https://www.santepubliquefrance.fr). Since 2003, 100 to 250 strains of Salmonella Typhi and Paratyphi infection, isolated in mainland France, have been reported to the CNR each year.(1) These strains come almost exclusively from imported cases (from Africa and the Indian subcontinent). However, small outbreaks (7 to 10 cases) linked to food-service establishments were identified in Paris in 2003 and 2006. In both cases, infections were traced to employees present within these food-service establishments who were healthy carriers. The existence of healthy carriers is a characteristic feature of these infections. After recovery from typhoid fever, 2 to 5% of individuals continue to harbor the pathogen (primarily in the gall bladder) without exhibiting any clinical signs. Bacteria from this reservoir are periodically excreted in carriers' stools, potentially causing new infections among their close contacts. Typhoid fever continues to be an endemic disease in the French national territory of Mayotte. In 2022, 111 laboratory-confirmed cases of typhoid fever were reported in this French département.(1
November 2024
- Annual reports of the CNR for Escherichia coli, Shigella and Salmonella
- GBD 2017 Typhoid and Paratyphoid Collaborators. The global burden of typhoid and paratyphoid fevers: a systematic analysis for the Global Burden of Disease Study 2017. Lancet Infect Dis. 2019 Apr;19(4):369-381