Close relationship of Crimean hemorrhagic fever-Congo (CHF-C) virus strains by neutralizing antibody assays.

Strains of Crimean hemorrhagic fever-Congo (CHF-C) virus originating in widely separated points representing diverse zoogeograhiczl and ecological areas were compared by a neutralization of fluorescent foci of infection-test, in an attempt to determine whether antigenic differences could be detected among the strains. Minor differences were found which could be confirmed by reciprocal kinetic neutralization tests with one-injection immune sera if the results were analyzed by linear regression. However, CHF-C virus strains cannot be reliably subdivided into geographic variants on the basis of the minor antigenic variations observed. In this apparent paucity of antigenic diversity over its wide distribution, CHF-C virus differs from other arboviruses with similar or even lesser distribution.