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Weil-Felix test

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A test for diagnosis of typhus and certain other rickettsial diseases. The blood serum of a patient with suspected rickettsial disease is tested against certain strains of (OX-2, OX-19, OX-K). The agglutination reactions, based on antigens common to both organisms, determine the presence and type of rickettsial infection.

In 1915, Weil and Felix showed that serum of patients infected with any member of the typhus group of diseases contains agglutinins for one or more strains of O X Proteus. In cases of typhus fever the reaction usually appears before the sixth day and reaches its height in the second week.

The test gave rise to much research to find why a specific agglutination reaction could be derived with an organism that apparently had no involvement in the causation of the disease.

We thank Merrick Roberts for information submitted.


  • E. Weil, A. Felix:
    Zur serologischen Diagnose des Fleckfiebers.
    Wiener klinische Wochenschrift, 1916, 29: 33-35. Untersuchungen über das Wesen der Fleckfieber-Agglutination.
    Wiener klinische Wochenschrift, 1917, 30: 393-399. Weitere Untersuchungen über das Wesen der Fleckfieberagglutination.
    Wiener klinische Wochenschrift, 1917, 30: 1509-1511.

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