Salmonella typhi, also known as typhoid fever, is an obligate parasite that has no known natural reservoir outside of humans. Worldwide, typhoid fever affects roughly 17 million people annually, causing nearly 600,000 deaths. The bacteria causes sudden onset of a sustained and systemic fever, severe headache, nausea, and loss of appetite. Mortality rates are falling in the US and developed nations, but the disease is still a serious risk. The bacteria’s highly contagious nature has lead to many high-profile outbreaks including the famous “Typhoid Mary” in early 20th century New York.
The encounter of humans to S. typhi is made via fecal-oral route from infected individuals to healthy ones. The bacterium that causes typhoid fever may be spread through poor hygiene habits and public sanitation conditions, and sometimes also by flying insects feeding on feces. Public education campaigns encouraging people to wash their hands after defecating and before handling food are an important component in controlling the spread of the disease.
Infection of S. typhi leads typhoid or enteric fever. Symptoms may vary from mild to severe and usually begin six to thirty days after exposure. Untreated typhoid fever cases result in mortality rates ranging from 12-30% while treated cases allow for 99% survival. Symptoms of infection include: