Which of the following is true regarding seasonal trend: (AIIMS Nov 11)
|A||Due to changes in herd immunity|
|B||Due to vector variation|
|C||Due to environmental factors|
|D||Due to vaccination|
Seasonal Trend is a well known characteristic of many communicable diseases. Seasonal variations of disease occurrence may be related to environmental conditions such as humidity, temperature, rainfall, overcrowding, and life cycle of vectors, etc. These factors directly or indirectly favor disease transmission. Examples of seasonal variation are:
- Measles and varicella are at peak in early spring.
- Upper respiratory infections increase during winter months.
- Gastrointestinal infections are common in summer months because of warm weather and rapid multiplication of vector flies.