Paratyphoid fever

Paratyphoid fever is a bacterial infection caused by one of three types of Salmonella enterica, specifically serotypes Paratyphi A, B, or C, which grow in the intestines and blood ^[1]. It is classified among the enteric fevers alongside typhoid fever, with humans as the sole infected animal reservoir ^[1].

Symptoms generally appear 6–30 days after exposure and commonly include a gradually rising high fever over several days, weakness, loss of appetite, and headaches ^[1]. Without treatment the illness may persist for weeks or months ^[1].

Factors outside the household, such as unclean food from street vendors and flooding, help distribute the disease from person to person ^[1]. Because of poverty and poor hygiene and insanitary conditions, the disease is more common in less-industrialized countries, principally owing to the problem of unsafe drinking water, inadequate sewage disposal, and flooding ^[1]. Occasionally causing epidemics, paratyphoid fever is found in large parts of Asia, Africa, and Central and South America, with many of those infected acquiring the disease in Asian countries ^[1]. About 16 million cases occur a year, resulting in about 25,000 deaths worldwide ^[1].

The bacteria are usually spread by consuming food or water contaminated with feces of an infected person, including instances where an infected food handler prepares meals ^[1]. Transmission may also occur through sexual contact, and external factors such as street-vendor food and flooding facilitate distribution ^[1]. Humans are the only animal reservoir of infection ^[1].

No vaccine exists specifically for paratyphoid, though typhoid vaccines may offer partial benefit, and prevention emphasizes drinking clean water and avoiding contaminated food sources ^[1]. Risk reduction is closely tied to sanitation improvements among poor, crowded populations ^[1].

1. 1 Wikipedia contributors. Paratyphoid fever - Wikipedia [Internet]. Wikipedia. cited 4 Sept 2026. Available from: https://en.wikipedia.org/wiki/Paratyphoid_fever