An assay for diagnosing infections caused by certain strains of Salmonella bacteria, specifically Salmonella Typhi and Salmonella Paratyphi, is called the Widal Test. Enteric fevers, including typhoid and paratyphoid fever, are brought on by these microorganisms. The way the test operates is by subjecting a patient’s serum to different Salmonella bacteria-derived antigens, and then monitoring the serum for agglutination reactions—a process in which antibodies attach to the antigens and form clumps. A positive Widal test indicates the existence of antibodies against Salmonella and typhoid or paratyphoid fever, either recently or in the past. Nonetheless, a number of factors need to be taken into account when interpreting the results, including previous vaccination history, the disease’s geographic prevalence, and the test’s timing in relation to the beginning of symptoms. Incorporating “(HHD)” indicates the particular version or context.