Typhoid fever is a systemic disease caused by Salmonella typhi and is the major cause of morbidity and mortality worldwide. Reports by the World Health Organization revealed that about 21 million cases and >600,000 annual deaths from typhoid fever occur throughout the world. Developing nations share the highest burden due to rapid population growth, increased urbanization, and limited safe water and health systems.
Accurate diagnosis of typhoid fever at an early stage is important not only for etiological diagnosis, but also to identify individuals that may serve as potential carriers, who may be responsible for acute typhoid fever outbreaks. Additionally, the diagnosis of typhoid fever on clinical grounds is difficult, as the presenting symptoms are diverse and similar to those observed with other febrile illnesses. Serodiagnosis of typhoid fever has been attempted since the late nineteenth century by Widal and Secard. The test is based on demonstrating the presence of agglutinins (antibodies) in the serum of an infected patient, against the H (flagellar) and O (somatic) antigens of Salmonella enterica serotype typhi (S. typhi).