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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 Factors:
- 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.
Host Factors:
- 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
- Immunization
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