1. Some ways in which communicable diseases spread areAirborne or droplet infection (e.g. colds, flu).Animal-borne or insect-borne infection (e.g. rabies, malaria, Lyme Disease).Bloodborne infection (e.g. HIV, hepatitis).Foodborne or waterborne infection (e.g. salmonella, giardia).Sexually transmitted (e.g. chlamydia, gonorrhoea, syphilis).Other direct contacts (e.g. some kinds of warts, scabies).Indirect contact (e.g. colds and flu carried from person to person on dirty tissues, money, doorknobs, phones, computer keyboards).

2. Diseases that are caused by the lack of some particular nutrient in a person's diet are called deficiency diseases. Eg: Iodine deficiency causes goitre.

3. Vaccination is the administration of antigenic material (a vaccine) to stimulate an individual's immune system to develop adaptive immunity to a pathogen. Vaccines can prevent or ameliorate infectious disease.

4. Obesity is a condition in which a person has excess body fat. Obesity occurs when people regularly eat more calories than they burn.

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