Measles in Victoria 1992 to 1996: the importance of laboratory confirmation.

Australia had a major measles epidemic in 1993 and 1994, which appeared to by-pass Victoria. Victorian notification and laboratory testing data for measles, and public hospital discharge codes, from 1992 to 1996, were reviewed. The rate of measles notification in Victoria fell between 1992 and 1996. By contrast the national notification rate increased markedly in 1993 and 1994. The proportion of measles tests performed at the Victorian Infectious Diseases Reference Laboratory (VIDRL) which were positive increased for all age groups in 1993 and 1994. This increase was highest for the 15 to 19 years age group. The hospital discharge codes demonstrated an increase in the number of admissions for measles in 1993 and 1994, largely for adolescents and younger adults. These data suggest Victoria had an age group specific measles outbreak, the magnitude of which was not reflected by the passive notification system. Reasons why younger age groups in Victoria appeared to avoid the epidemic are unclear.