A serological agglutination reaction to detect serum agglutinins to Salmonella typhi and related organisms. It has limited sensitivity and specificity. It is being phased out and replaced as a diagnostic test, but it remains a useful prognostic test for typhoid and related salmonelloses, as the titer declines during recovery. The test was developed by the French bacteriologist Georges Widal (1862–1929).
Subjects: Public Health and Epidemiology.