[A study on seasonal variation of epidemic cerebrospinal meningitis with circular distribution method].

In order to study the seasonal variation of epidemic cerebrospinal meningitis (ECM) incidence; the data of ECM incidence during the period 1959-1990 in Changde City were analysed with circular distribution method. The result showed that the seasonal variation was obvious. In 28 of these 32 years, the highest peak of the ECM incidence occurred in March. In 26 years, 95% of epidemic periods began from October to June of the next year. The annual incidence rate had positive correlation with the r value of circular distribution, negative correlation with angular deviation and no correlation with mean angle a. It is concluded that the annual incidence rate concerns with the seasonal variation and does not concern with the date of the highest peak.