Encephalitis surveillance annual summary : 1964

During 1964, a total of 3587 cases of encephalitis, including 337 deaths, was reported to the Encephalitis Surveillance Unit (ESU). This represents the highest total of cases reported to the ESU since it was established in 1955. An increased number of both post-infectious and primary encephalitis cases was reported in 1964 as compared to 1963. Mumps and measles accounted for over three quarters of the 1585 post- infectious encephalitis cases. The widespread rubella epidemics during the winter of 1964 were reflected by a relatively large number (59) of reported post-rubella encephalitis cases. During 1964, 582 cases of arthropod-borne encephalitis were reported. Outbreaks due to St. Louis, Western Equine, and California encephalitis viruses occurred during 1964. Cases of human illness due to Eastern Equine encephalitis virus were reported for the first time in three years. A summary of this material as well as information on virus isolations from non-human species are summarized in Section II,Detailed reports of the outbreaks of arthropod-borne encephalitis occurring during 1964 are contained in Section III. Major epidemics of St. Louis encephalitis were recorded in Harris County (Houston), Texas, and in Burlington and Camden Counties, New Jersey, (including adjacent areas of Pennsylvania). St. Louis encephalitis outbreaks of smaller size occurred in Indiana, Tennessee, Kentucky, and in two separate areas of Illinois. Outbreaks of mixed infection with both St. Louis encephalitis and Western Equine encephalitis were recognized in the high plains area of Texas and in central Colorado. The first recognized outbreak due to California encephalitis virus was noted in Indiana, in 1964.A summary of viral encephalitis cases in horses reported to the U.S. Department of Agriculture has been previously included in this report. This will appear as a supplement to the 1964 Encephalitis Surveillance Report in several months.I. Summary -- II. Morbidity trends - 1964-- III. State reports -- IV. Special reports.196