Typhoid fever is an highly infectious disease caused by the bacterium Salmonella Typhi. The primary mode of transmission is through the consumption of contaminated food and water containing the bacteria. Once ingested, the bacteria establish themselves in the intestines and subsequently enter the bloodstream.

Another significant route of transmission is via human waste (urine and feces). Contaminated wastewater mixing with drinking water can lead to the spread of the disease. Furthermore, indirect transmission can occur if an infected person, after insufficient hand hygiene, touches surfaces or objects that are then touched by others.

While treatable with antibiotics and preventable by vaccination, some individuals can carry the Salmonella Typhi bacteria for years without showing symptoms; this condition is known as chronic typhoid. It is crucial to note that typhoid fever is transmitted exclusively from human to human and does not originate from animals.