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What is Cyclic trends are seen in which of the following and explain in detail?
.some disease occur in cycles spread over sho periods of time which may be days ,weeks,or months.or years.for example measles in pre vaccination era appeared in cycles with major peaks every 2 to 3 years and rubella every 6 or 9 years.this was due to naturally occurring variations in herd immunity. ref:park&;s textbook,ed 22,pg no 62