Typhoid is a major health problem throughout the world. Globally, there are more than 21 million cases of typhoid each year, with more than 700,000 deaths. It is especially prevalent in developing countries such as Pakistan. Early detection of the disease is very important for its control, but unfortunately, definitive diagnostic procedures are not available. 10 Widal test and blood culture remain the only universally practiced diagnostic procedures, because other methods are either invasive, have failed to prove their utility, or are expensive.
Widal test is quite sensitive but has become highly nonspecific.
Another shortcoming of the Widal test is that it becomes positive only in the second week of illness, so its value for early detection of the disease is limited. Accepted for publication 13 April 1999. Hybridization by using DNA probes was the first molecular biology technique used for the diagnosis of typhoid fever. It is specific but its sensitivity is poor. The advent of PCR technology has provided unparalleled sensitivity and specificity for the diagnosis of typhoid.