Typhoid and paratyphoid fever are caused by bacteria from the genus Salmonella. Humans are the only reservoir for the bacteria, which belong to 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.
One to three weeks after infection, patients begin to suffer from constant fever, headache, anorexia, weakness and abdominal pain with diarrhea or constipation.
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 intestine, 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.
Appropriate antibiotic therapy reduces the mortality risk to less than 1%. Fluoroquinolones (ciprofloxacin) and third-generation cephalosporins are the most commonly used antibiotics for treating typhoid and paratyphoid fever. However, more and more antibiotic-resistant strains are being isolated, particularly in South 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). These strains originating from South Asia are being closely monitored by the CNR.
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.
The most recent data suggests that there are more than 20 million cases of typhoid and paratyphoid fever worldwide each year, and more than 200,000 deaths (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 cases of Salmonella Typhi 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 of their close contacts. Typhoid fever continues to be an endemic disease in the French national territory of Mayotte. In 2019, 53 laboratory-confirmed cases of typhoid fever were reported in this French department (3).
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.
A well-tolerated typhoid vaccine which requires only a single injection can be administered to those traveling to areas at risk. The vaccine lasts for three years and provides 60% protection in endemic areas.
At the Institut Pasteur
The National Reference Center for Escherichia coli, Shigella and Salmonella, hosted in the Enteric Bacterial Pathogens Unit (led by François-Xavier Weill) at the Institut Pasteur, is involved in salmonellosis surveillance.
The Institut Pasteur teams working on the topic
led by François-Xavier Weill
Surveillance and public health
led by François-Xavier Weill
1. Rapport d’activité annuel 2019. Année d’exercice 2018. https://www.pasteur.fr/fr/sante-publique/CNR/les-cnr/escherichia-coli-shigella-salmonella/rapports-d-activite.
2. OMS (Organisation Mondiale de la Santé), 2018. Normes de surveillance des maladies évitables par la vaccination. Fièvre typhoïde et autres salmonelloses invasives. https://www.who.int/docs/default-source/immunization/vpd_surveillance/vpd-surveillance-standards-publication/fi%C3%A8vre-typho%C3%AFde-(derni%C3%A8re-mise-%C3%A0-jour-le-5-septembre-2018).pdf?sfvrsn=993904a6_10
3. Fièvres typhoïde et paratyphoïde. Maladies à prevention vaccinale. https://www.santepubliquefrance.fr/maladies-et-traumatismes/maladies-a-prevention-vaccinale/fievres-typhoide-et-paratyphoide/donnees/#tabs