Typhoid fever is an acute illness characterised by fever arising from the Salmonella enterica serotype Typhi bacteria. It can also be due to Salmonella paratyphi, being an associated bacterium that usually causes a less severe illness. The bacteria are accumulated in water or food by a human carrier and are then spread to other people in the area.
The bacterium strives in the intestinal areas and bloodstream of humans. It circulates between individuals by direct contact with the faeces of an infected person. S. Typhi enters via the mouth and stays for about 1 to 3 weeks in the intestine area. After this, it passes along the wall of the intestine and finally into the circulatory system.
From there, it moves into adjoining tissues and organs as well. The immune system of the individual is unable to fight back because S. Typhi can live within the host’s cells, safe from the immune system.
Typhoid fever is caused either by drinking or eating the bacteria which is present in contaminated water or food items. People with acute onset of infection can pollute the nearby water supply by means of stool, which has a high concentration of the bacteria. Contamination of the water supply can, in turn, taint the food supply. The bacteria can remain for weeks in water or dried sewage.