(a) What is meant by communicable disease? Name any two communicable diseases. (b) What are the various ways in which communicable diseases can occur and spread?

Communicable diseases, also called infectious or contagious diseases, are illnesses caused by pathogenic microorganisms (bacteria, viruses, fungi, parasites) that can be transmitted directly or indirectly from one person to another, or from animals to humans. These diseases spread when pathogens leave an infected host and successfully enter a susceptible individual, establishing infection in the new host. Two common examples are tuberculosis (TB), a bacterial infection primarily affecting the lungs caused by Mycobacterium tuberculosis and spread through airborne droplets when infected individuals cough or sneeze, and cholera, a severe bacterial diarrheal disease caused by Vibrio cholerae transmitted through contaminated water and food.

Communicable diseases spread through multiple transmission routes. Direct contact transmission occurs through physical touching, kissing, sexual contact, or mother-to-child transmission during pregnancy, childbirth, or breastfeeding (examples: HIV, herpes, syphilis). Indirect contact happens through contaminated surfaces, objects, or fomites that transfer pathogens to new hosts (examples: common cold, influenza). Airborne transmission involves pathogens suspended in air droplets or dust particles inhaled by others (examples: tuberculosis, measles, chickenpox, COVID-19). Waterborne and foodborne transmission occurs when pathogens contaminate drinking water or food (examples: cholera, typhoid, hepatitis A). Vector-borne transmission requires insects or animals to transfer pathogens between hosts (examples: malaria via mosquitoes, rabies via animal bites, plague via fleas). Prevention strategies target these transmission routes through hygiene practices, safe water and food handling, vaccination, vector control, quarantine of infected individuals, and public health education.