How do communicable disease in human populations may be prevented or controlled?
Depends on the disease but very simply, you need to understand the pathway that the particular organism follows and then break the chain; e.g. 1) Food-borne illnesses can be prevented or controlled by good hygiene (such as avoiding cross-contamination from raw meats to cooked foods), refrigerated storage (to prevent the multiplication of bacteria) and thorough cooking to destroy them. 2) In the case of air-born transmission (droplets) (like colds and flu) these can be prevented or controlled by keeping people who are infected away from those that are not – e.g. isolation, closing schools, etc. Masks are thought to be of limited value other than to catch your own sneezes and cough droplets. 3) Where available, vaccines can be used to reduce susceptibility.
