Accidents happening during weekends is -
Ans. (a) Cyclic trendsRef : K. Park 23rd ed. / 65-66, 21st ed / 61,62Time Distribution of Disease* Secular trend: it implies changes in occurrence of a disease over a period of long time, generally several years or decade.# Ex: Polio, Diphtheria, Pertusis are the diseases which are reducing in India in fast few decades; and diseases like DM, Obesity and hypertension has increased in past few decades.* Epidemic: Short term fluctuation of a Disease occur in few days, week, or months. E.g. food poisoning, Bhopal gas tragedy* Cyclic trends: some diseases occur in cycles spread over a period of time which means days, weeks, months, or years. Non-infectious condition may also show periodic fluctuations ex: automobile accidents in US are more frequent on weekends, esp: Saturday. Other examples can be measles occurring every 2-3 years, Rubella every 6-9 years.* Seasonal trend: It is seasonal variation/fluctuation in occurrence of a disease. Ex: measles, URI, GIT infection.
Cyclic trends
Seasonal trends
Secular trends
Point source epidemic
Concept of disease causation