You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is Seasonal trend is due to: and explain in detail?
Ans. (d) All of the above* Periodic fluctuations:Seasonal trends:1. Is seasonal variation/fluctuation in occurrence of a disease2. Is due to vector variation, environmental factors and change in herd immunity3. Examples:i. Measles (early spring)ii. Upper respiratory infections (winters)iii. Gastrointestinal infections (summers)Cyclical trends:1. Is occurrence of a disease in cycles spread over short periods of time, which may be days, weeks, months or years2. Examples:i. Measles (every 2-3 years)ii. Rubella (every 6-9 years)iii. Influenza pandemics (every 10-15 years)