Which of the following can be diagnosed with the Widal test?

Typhoid fever

The correct answer is Option (3) - Typhoid fever

The Widal test is used for the diagnosis of: Typhoid fever

The Widal test is a serological test used to detect antibodies specific to Salmonella enterica serotype Typhi, the bacteria responsible for causing typhoid fever. This test is based on the principle of agglutination, where the patient's serum is mixed with antigens derived from Salmonella Typhi. If the patient has been infected with Salmonella Typhi and has developed antibodies against it, the antibodies will react with the antigens, causing visible clumping or agglutination. The presence of significant agglutination indicates a positive result for typhoid fever.

The Widal test is not used for diagnosing AIDS, cancer, or tuberculosis.