- Clinical science
Typhoid and paratyphoid fever are infectious diseases caused by the bacteria Salmonella typhi and Salmonella paratyphi. Transmission occurs via the fecal-oral route. The incubation period is typically 7–21 days, although it may be as long as 30 days. Typhoid and paratyphoid fever classically have three clinical stages. In the first week of symptoms, body temperature rises gradually and relative bradycardia as well as diarrhea or constipation may occur. The second week of illness is characterized by persistent fever, rose-colored spots on the abdomen, nonspecific abdominal pain, and profuse diarrhea. During the third week, complications such as hepatosplenomegaly, intestinal bleeding, and/or perforation with secondary bacteremia and peritonitis may occur. Symptoms begin to subside in the fourth week. Pathogen detection in blood and stool cultures confirms the diagnosis. The treatment of choice includes fluoroquinolone antibiotics such as ciprofloxacin. Up to 6% of patients become chronic carriers after symptoms have resolved.
- Globally, there are an estimated ∼ 22 million cases occur per year.
Epidemiological data refers to the US, unless otherwise specified.
- Direct: person-to-person contact; asymptomatic carriers are frequently involved
- Indirect: contaminated food and water
Humans are the main reservoir for Salmonella typhi!
- Oral uptake of pathogen: A relatively large number of organisms (∼ 105) are needed to cause infection (infective dose), unlike, e.g., Shigella, where as few as ∼ 10 organisms suffice to infect the host.
- Distal ileum: migration into the Peyer patches; . If the pathogen manages to reach the distal ileum, it migrates via M cells through the epithelium and into the Peyer patches.
- Infection of macrophages → nonspecific symptoms
- Spread from macrophages to the bloodstream: septicemia → systemic disease
- Migrates back to intestine → excretion in feces
- Incubation period: 5–30 days (most commonly 7–14 days)
- If left untreated, three different disease stages, each lasting a week, classically occur.
- After 3 weeks of disease: slow regression of symptoms; patients may become (see “complications” below)
Typhoid fever is a systemic disease; it is not limited to the gastrointestinal system!
Progression of illness
- Persistent fever , but no chills; mostly unresponsive to antipyretics
- Nonspecific abdominal pain and headaches
- Rose-colored spots: : In 30% of patients, a small, speckled, and rose-colored exanthem appears on the lower chest and abdomen (most commonly around the navel).
- Typhoid tongue: greyish/yellowish-coated tongue with red edges
- Yellow-green diarrhea; , comparable to pea soup (caused by purulent, bloody necrosis of the Peyer patches), or obstipation and bowel obstruction (as a result of swollen Peyer patches in the ileum)
- Neurological symptoms (delirium, coma)
- Clinical features of week 2
- Additional possible complications include:
- Laboratory tests
- Pathogen detection
Blood culture is the most important diagnostic tool at disease onset, as stool cultures are often negative despite active infection!
- First-line treatment: fluoroquinolone antibiotics (e.g., )
- Azithromycin, if resistance to fluoroquinolone antibiotics is suspected (e.g., in patients with infection acquired from certain regions, such as South Asia)
- Third-generation cephalosporins (e.g., ) are preferred for severe infection.
- Definition: positive stool cultures 12 months after overcoming the disease
- Incidence: up to 6% of the patients become chronic carriers
Presentation: typically asymptomatic
- Increased risk for gallbladder cancer
Treatment: fluoroquinolones (e.g., ciprofloxacin) administered for at least 1 month
- Chronic carriers are not allowed to work in the food industry.
We list the most important complications. The selection is not exhaustive.
Food and water
Vaccination is not entirely effective. Measure must therefore be implemented to avoid exposure (see ).
- Indication: The WHO recommends typhoid fever vaccination to those traveling to high-risk areas (East and Southeast Asia, South and Central America, Africa).
- Administration: A parenteral, inactivated vaccine and an oral, live vaccine are available for active immunization, and both provide similar levels of protection.