Typhoid

Facts & figures

21 million

cases annually

222,000 typhoid-related

deaths annually

90% of morbidity and mortality

in Asia

Public health

Typhoid fever is a systemic infection that remains a significant public health problem in developing countries, primarily in Asia.

A threat to vulnerable populations in low-income countries

Transmission

Typhoid fever is a systemic infection caused by the bacterium Salmonella enterica serovar Typhi, usually through the ingestion of contaminated food or water. Infection is transmitted via the fecal-oral route and the disease is associated with poor hygiene, lack of clean drinking water and inadequate sanitation.

Humans are the only known affected host, and disease is almost exclusively spread by ingestion of food or water contaminated with excreta from typhoid fever cases or asymptomatic carriers. Bacteria can survive for prolonged periods in water, ice, dust and dried sewage and these may become sources of infection.

Polluted water is the most common source of typhoid transmission.

Epidemiology

Although typhoid is largely considered an endemic disease, epidemics do occur, often as a result of contamination or breakdowns in water supplies and sanitation systems.

The infection is particularly frequent in school-aged children.

Typhoid-related deaths primarily affect Asia. In Africa, estimates of the disease burden are limited by insufficient data.

Symptoms

The acute illness is characterized by prolonged fever, headache, and nausea, loss of appetite, and constipation or sometimes diarrhea. Symptoms are often non-specific and clinically non-distinguishable from other febrile illnesses.

However, clinical severity varies and severe cases may lead to serious complications or even death. Constipation usually occurs in older children and adults, whereas younger children may suffer from diarrhea. The illness can last for several weeks and even months. The most frequent complications include delirium and shock, gastro-intestinal bleeding, and intestinal perforation.

Treatment & Prevention

Typhoid fever can be effectively treated with antibiotics, but growing rates of antibiotic resistance in many regions are making this treatment option increasingly difficult and costly.

In terms of prevention, two typhoid vaccines are currently recommended:

  1. an injectable polysaccharide vaccine based on the purified Vi antigen (known as Vi-PS vaccine) for persons aged two years and above;
  2. a live attenuated oral Ty21a vaccine in capsule formulation for those over five years of age. WHO recommends the use of the Vi-PS and Ty21a vaccines to control endemic disease and for outbreak control.

In addition, WHO recommends that all typhoid fever vaccination programs should be implemented in the context of other efforts to control the disease, including health education, water quality and sanitation improvements, and training of health professionals in diagnosis and treatment.

Several Vi polysaccharide–protein conjugate vaccine candidates are under development (or are nationally licensed but not on the international market) and anticipated to be available in the future for infant immunization.