Life Cycle of Typhoid

Typhoid is a deadly illness that is caused by the Salmonella Typhi bacterium. About 400 cases of typhoid occur in the United States each year. However, three-quarters of those are contracted while travelling abroad, where it affects nearly 21.5 million people.

It is less common in other industrialised regions such as Canada, Western Europe, Japan and Australia, according to


Typhoid is a bacterial infection. Its most common symptoms are diarrhoea, systemic disease and a skin rash. It is sometimes called enteric fever, and is potentially lethal if not diagnosed and treated soon enough. It thrives in conditions with bad or no sanitation, crowding and general social chaos. It is possible that typhoid caused the Great Plague of Athens that ended the Peloponnesian War, according to the World Health Organization.


Salmonella Typhi infection is unique to humans. The infection enters through the intestinal tract and moves into the blood stream, then into organs such as the spleen and gallbladder. Those who are infected carry the bacteria in their blood. Very few people recover from typhoid but continue to carry the bacteria without showing symptoms. According to the Centers for Disease Control and Prevention, “Both ill persons and carriers shed S. Typhi in their faeces.” In areas with poor sanitation, urine and faeces contaminate the food or water, leading to mass infections.


The incubation period is one to three weeks, where the bacterium multiplies in the bloodstream. Symptoms develop between one and three months after exposure and can be very mild or quite severe. Symptoms include fever and headache, constipation or diarrhoea, an enlarged spleen and liver and rose-coloured spots on the chest. General ill feeling and severe abdominal pain with a high fever, over 39.4 degrees Celsius, are the most common. The fever is often difficult to diagnose since the symptoms are similar to many bacteria and viral infections, specifically the common cold.


When left untreated, typhoid can progress to delirium, internal bleeding and death within just one month. According to eMedicine, “Survivors may be left with long-term or permanent neuropsychiatric complications.” It may be treated with common antibiotics, although antibiotic resistance is quite widespread. Intravenous fluids and electrolytes keep the patient hydrated. Symptoms often disappear before the bacteria is completely irradiated, so patients must make sure to take medication for the entire length of the prescription.


You can protect yourself from the bacteria using vaccines. They are usually recommended before any travel outside the U.S., Canada, Northern and Western Europe or Australia and New Zealand. According to The New York Times, “Adequate water treatment, waste disposal, and protection of food supply from contamination are important public health measures.” Typhoid carriers should never work as food handlers.