Typhoid (ORPHA:99745)
Typhoid or typhoid fever is a reportable, fecal-oral, potentially fatal infectious disease, caused by the bacteria Salmonella typhi and characterized by a non-focal fever.
Epidemiology
The prevalence of typhoid is unknown but it is most commonly found in Asia, Africa and South America where access to properly treated drinking water may be limited. It is rare in Europe and Western countries and generally only occurs when imported from an endemic location. The annual incidence in Europe is estimated to be less than 1/30,000 persons/year.
Clinical description
Symptoms usually appear 1-7 days after ingestion of the bacteria and include high fever (39 to 40°C), chills, constipation or diarrhea, headache, stomach pain, malaise, rash of flat rose-colored spots on the chest and hepato-splenomegaly. Temperature rises for 2-3 days and remains elevated for another 10-14 days accompanied by bradycardia and prostration. In severe cases, delirium, stupor and coma can occur. In 1-2% of patients, intestinal lesions can lead to bleeding and death. Others may develop pneumonia in the second to third week. Intestinal hemorrhage and perforation (usually in the terminal ileum) is a serious complication that can occur 2-3 weeks after infection, and usually occurs in developing countries where treatment is not always available. The convalescence period may last several months. Patients can remain carriers after symptoms disappear. With treatment most patients recover after 5-7 days of therapy and death is extremely uncommon.
Etiology
Typhoid is caused by several serovars of Salmonella enterica, a Gram-negative bacterium, with S. typhi being the most common. It is transmitted by the fecal-oral route from human to human when food or water is contaminated with feces of infected individuals. There is no known zoonotic reservoir. Once ingested,  S. typhi multiply inside macrophages and spread throughout the body in the bloodstream where they travel to the bone marrow, liver and gallbladder and are shed in the bile and feces. Asymptomatic carriers can spread the disease as a consequence of gallbladder colonization.
Diagnostic methods
Diagnosis of typhoid is suspected in patients with fever who have recently travelled to an area where the disease is endemic. The only methodology currently able to categorically confirm a diagnosis of typhoid involves a microbiological culture of blood or bone marrow to detect S. typhi or other typhoidal organisms. The Widal test, an agglutination test, is used only in developing countries as it is rapid, inexpensive and does not require a specialized laboratory, but it lacks sensitivity and specificity.
Differential diagnosis
Other viral, bacterial or parasitic pathogens that cause diseases similar to typhoid include malaria, dengue fever, leptospirosis, typhus group rickettsia (see these terms), and influenza.
Management and treatment
Typhoid is treated with antimicrobials, typically fluoroquinolones, which are essential for bacterial clearance. Patients usually begin to recover after 2-3 days but must complete the course of treatment to prevent relapse or latent retention of the infection. If intestinal perforation occurs, surgical intervention is necessary immediately. When travelling to countries where typhoid is endemic, vaccinations are recommended. The two licensed vaccines currently available are the oral live attenuated vaccine Ty21a and the parenteral Vi polysaccharide vaccine. Travelers should take care to avoid unsafe drinking water and food prepared in unsanitary conditions. Any cases of typhoid should immediately be reported. Food should not be prepared by people who have been infected with typhoid recently as they may still be carriers.
Prognosis
Prognosis is good and complications rarely occur if treated quickly with antibiotics. In untreated cases the fatality rate can be as high as 20%.

                            Last update: 
                            January 2013


                            - Expert reviewer(s): 
                             Stephen BAKER