Paratyphoid fever

Cause and transmission

The illness results from infection with Salmonella paratyphi (several closely related serotypes). The bacteria pass from an infected person into the environment through stool and sometimes urine, and then enter a new host by the fecal–oral route. Contaminated drinking water, raw or undercooked food, and poor hand hygiene are common sources. Long-term carriage in the gallbladder or biliary tract can allow ongoing shedding of organisms even after symptoms resolve.

Signs and symptoms

Symptoms generally develop after an incubation period of days to weeks and can range from mild to severe. Typical features include:

• Persistent fever that rises gradually and may last several days to weeks
• Abdominal discomfort, diarrhea or constipation, and abdominal pain
• Enlargement of the liver or spleen (hepatosplenomegaly)
• Relative slow heart rate (a finding sometimes seen in febrile illnesses)
• Other complaints can include headache, malaise, anorexia and, occasionally, a faint rash.

Complications and carrier state

Most uncomplicated cases resolve with appropriate care, but complications may occur, especially if diagnosis or treatment is delayed. These include intestinal bleeding, perforation, or systemic spread of infection. A minority of people become chronic carriers and continue to excrete the bacteria for months or longer; such carriers are important in sustaining transmission in communities.

Diagnosis and treatment

Definitive diagnosis is made by isolating the organism from blood, stool or other clinical specimens. Serologic tests exist but have limitations. Management relies on appropriate antibiotic therapy guided by local resistance patterns, supportive care (fluids, nutrition, fever control), and attention to complications. Effective antibiotic treatment shortens illness, reduces complications and lowers the risk of becoming a long-term carrier.

Prevention and public health

Prevention focuses on safe water, sanitation, food hygiene and handwashing. Vaccines that target S. typhi do not reliably protect against all paratyphi strains, so preventive measures and surveillance remain crucial in endemic areas. Public-health responses to outbreaks emphasize identifying the source, treating cases, screening food handlers when indicated, and educating communities about hygiene.

For further reading, basic reference sources and public-health guidance can be consulted via authoritative links and national health services; see pathogen overview and comparative materials on typhus and related febrile illnesses.