Typhoid fever is the result of systemic infection by Salmonella typhi found only in man. The disease is characterized by typical continuous fever fro 3-4 weeks. The term enteric fever includes both typhoid and paratyphoid fevers.
- Agent: the causative agent of typhoid is S. typhi. The organism survives intracellularly in the tissues of various organs. It is readily killed by drying, pasteurization and common disinfectants.
- Reservoir of Infection: human being is the only known reservoir of infection; he may be a case or a carrier.
- Source of Infection: primary source of infection are faeces and urine of cases or carriers. Secondary sources are contaminated water, food, fingers and flies. The bacilli are not excreted in sputum or milk.
- Age: typhoid affects all ages. However, the attack rate is highest in children of 5-19 years.
- Sex: more cases are reported among males than females. But carrier rate is more in females.
- Immunity: all ages are susceptible. Antibody may be stimulated by infection or by immunization.
Environmental and Social Factors:
Though the incidence is reported all through the year, peak incidence is reported during July-September i.e. the rainy season and increased fly population. The bacilli are also found in water, ice, food and soil. Vegetables grown in sewage water might be a source of contamination.
Social factors include pollution of drinking water supplies, open air defecation, open air urination, low standards of food and personal hygiene and health ignorance.
Mode of Transmission: Transmission occurs through fecal-oral or urine-oral route. The transmission is possible through contaminated food, water, soil. Flies play a significant role in transmission.
Incubation Period: usually 10-14 days. Ranges between 3 days to 3 weeks.
Clinical Features: the onset is insidious, in children starts with chills and high fever. Symptoms include malaise, headache, cough and sore throat with abdominal pain and constipation. Fever ascends in a step ladder fashion, reaches normalcy after 7-10 days. The patient looks toxic, exhausted accompanied with constipation or ‘pea soup’ diarrhoea.
Control: Control or elimination of typhoid fever is within the reach of modern public health. Three lines of defence against typhoid fever are-
- Control of reservoir
- Control of sanitation