Complete Biology notes on Communicable and Non-Communicable diseases for BPSC and Other Competitive Exams in 2025
General Science- 18 (Biology)
Communicable and Non-communicable diseases, Prevention & Vaccination
Understanding diseases, their types, causes, and prevention strategies is fundamental to public health and a crucial topic for the Competitive Exams.
1. What are Diseases?
A disease is any condition that impairs the normal functioning of the body or mind. It can be caused by infections, genetic defects, environmental factors, or lifestyle choices.
2. Types of Diseases
Diseases are broadly classified into two main categories: Communicable and Non-communicable.
A. Communicable Diseases (Infectious Diseases):
- Definition: Diseases that can spread from one person to another (or from animals to humans) directly or indirectly, through an infectious agent (pathogen).
- Causes: Caused by microscopic organisms called pathogens.
- Viruses: (e.g., Common cold, Influenza, HIV/AIDS, Measles, Dengue, Chikungunya, COVID-19, Polio, Hepatitis).
- Bacteria: (e.g., Tuberculosis, Cholera, Typhoid, Tetanus, Pneumonia, Diphtheria, Pertussis).
- Fungi: (e.g., Ringworm, Athlete’s foot).
- Protozoa: (e.g., Malaria, Amoebiasis, Kala-azar – Leishmaniasis).
- Modes of Transmission:
- Direct Transmission:
- Direct Contact: Touch (skin infections), kissing (herpes), sexual contact (STIs like HIV, Syphilis).
- Droplet Infection: Coughing, sneezing, talking (influenza, common cold, COVID-19, TB).
- Vertical Transmission: From mother to child during pregnancy or childbirth (HIV, Syphilis).
- Indirect Transmission:
- Vehicle-borne: Contaminated food (Typhoid, Cholera), water (Cholera, Hepatitis A), or fomites (objects like doorknobs, toys carrying germs – common cold).
- Vector-borne: Transmitted by living organisms (vectors) like insects.
- Mosquitoes: Dengue, Malaria, Chikungunya, Japanese Encephalitis, Filaria.
- Flies: Typhoid, Cholera.
- Ticks/Mites: Scrub Typhus.
- Airborne: Pathogens suspended in air particles for long periods (Measles, Tuberculosis, Chickenpox).
B. Non-communicable Diseases (NCDs / Chronic Diseases):
- Definition: Diseases that are not spread from person to person. They are generally long-lasting and result from a combination of genetic, physiological, environmental, and lifestyle factors.
- Causes:
- Lifestyle Factors: Unhealthy diet, lack of physical activity, tobacco use, excessive alcohol consumption.
- Genetic Factors: Predisposition to certain diseases.
- Environmental Factors: Exposure to pollution, toxins.
- Aging: Natural wear and tear of the body.
- Examples:
- Cardiovascular Diseases (CVDs): Heart attack, stroke, hypertension (high blood pressure).
- Diabetes: Type 1 and Type 2 (most common).
- Cancer: Various types.
- Chronic Respiratory Diseases: Asthma, Chronic Obstructive Pulmonary Disease (COPD).
- Nutritional Deficiency Diseases:
- Anemia: Iron deficiency.
- Goiter: Iodine deficiency.
- Night Blindness: Vitamin A deficiency.
- Rickets/Osteomalacia: Vitamin D deficiency.
- Scurvy: Vitamin C deficiency.
- Beriberi: Vitamin B1 deficiency.
- Pellagra: Vitamin B3 deficiency.
- Kwashiorkor/Marasmus: Protein/Protein-Energy Malnutrition.
3. Prevention of Diseases
Prevention strategies differ for communicable and non-communicable diseases.
A. Prevention of Communicable Diseases:
- Hygiene and Sanitation:
- Personal Hygiene: Frequent handwashing (especially before eating and after using the toilet), bathing, oral hygiene.
- Environmental Sanitation: Proper disposal of waste, safe drinking water supply, proper sewage treatment.
- Safe Food and Water:
- Boiling water, using water purifiers.
- Washing fruits and vegetables thoroughly.
- Cooking food properly and storing it safely.
- Vector Control:
- Eliminating breeding grounds for mosquitoes (stagnant water).
- Using mosquito nets, repellents.
- Insecticide sprays.
- Isolation and Treatment:
- Isolating infected individuals to prevent spread.
- Early diagnosis and appropriate treatment of diseases.
- Vaccination: One of the most effective methods (discussed in detail below).
- Public Awareness: Educating communities about disease transmission and prevention.
B. Prevention of Non-communicable Diseases:
- Healthy Lifestyle:
- Balanced Diet: Rich in fruits, vegetables, whole grains; low in saturated/trans fats, sugar, and salt.
- Regular Physical Activity: At least 30 minutes of moderate intensity exercise most days of the week.
- Avoidance of Tobacco and Alcohol: Smoking and excessive alcohol consumption are major risk factors for many NCDs.
- Stress Management: Chronic stress can contribute to NCDs.
- Regular Health Check-ups: Early detection and management of risk factors (e.g., high blood pressure, high cholesterol, high blood sugar).
- Environmental Control: Reducing exposure to air pollution and other environmental toxins.
4. Vaccination
Definition: Vaccination (or immunization) is the process by which a person is made immune or resistant to an infectious disease, typically by the administration of a vaccine.
Principle of Vaccination (Immunity):
- Vaccines contain weakened or inactivated forms of a pathogen, or parts of a pathogen (e.g., proteins, sugars), or genetic material (mRNA/DNA) that code for specific pathogen components.
- When a vaccine is administered, the immune system recognizes these components as foreign.
- The immune system then produces antibodies (proteins that neutralize pathogens) and memory cells.
- If the vaccinated person later encounters the actual pathogen, the memory cells rapidly recognize it and mount a strong, quick immune response, preventing or significantly reducing the severity of the disease.
Types of Vaccines (Basic understanding):
- Live-attenuated Vaccines: Contain a weakened form of the living virus/bacteria. Elicit a strong, long-lasting immune response. (e.g., MMR (Measles, Mumps, Rubella), Oral Polio Vaccine (OPV), BCG (for TB), Chickenpox, Rotavirus).
- Inactivated (Killed) Vaccines: Contain a killed version of the pathogen. (e.g., Injectable Polio Vaccine (IPV), Rabies, Hepatitis A, whole-cell Pertussis).
- Toxoid Vaccines: Use inactivated toxins produced by bacteria to generate immunity against the toxin’s harmful effects. (e.g., Diphtheria, Tetanus).
- Subunit/Recombinant/Polysaccharide Vaccines: Use specific pieces of the pathogen (e.g., proteins, sugars, capsular polysaccharides) to trigger an immune response. (e.g., Hepatitis B, Pneumococcal, HPV, Acellular Pertussis).
- mRNA/Viral Vector Vaccines: Newer technologies using genetic material to instruct the body’s cells to make a protein fragment of the pathogen, triggering an immune response. (e.g., some COVID-19 vaccines).
Importance of Vaccination:
- Individual Protection: Protects the vaccinated person from serious illness.
- Herd Immunity (Community Immunity): When a significant portion of a population is immune to a disease (through vaccination or prior infection), it provides indirect protection to those who are not immune. This reduces the spread of the disease.
- Disease Eradication/Elimination: Successful vaccination campaigns have led to the eradication of smallpox globally and the near-eradication of polio in many parts of the world.
Key Vaccination Programs/Diseases in India: India has a robust Universal Immunization Programme (UIP) that provides free vaccines against 12 vaccine-preventable diseases.
- BCG (Bacillus Calmette-Guérin): For Tuberculosis (TB).
- OPV (Oral Polio Vaccine) / IPV (Inactivated Polio Vaccine): For Polio. (India declared polio-free in 2014, but vaccination continues to maintain immunity).
- Pulse Polio Immunization Program: Mass vaccination campaigns to eradicate polio.
- DPT (Diphtheria, Pertussis (Whooping Cough), Tetanus): Combination vaccine.
- Measles: For Measles.
- Rubella: Often combined with Measles (MR vaccine) or Mumps (MMR vaccine).
- Hepatitis B: For Hepatitis B infection.
- Japanese Encephalitis (JE): In endemic areas.
- Rotavirus Vaccine: For Rotavirus diarrhea.
- Pneumococcal Conjugate Vaccine (PCV): For pneumococcal diseases (pneumonia, meningitis).
- Typhoid Conjugate Vaccine (TCV): For Typhoid.
- COVID-19 Vaccines: Latest addition to combat the pandemic.
Practice Questions
- Which of the following diseases is caused by a virus?
- A) Tuberculosis
- B) Malaria
- C) Cholera
- D) Dengue
- Rationale: Dengue is a viral infection transmitted by mosquitoes, while TB is bacterial, Malaria protozoan, and Cholera bacterial.
- A disease that is transmitted through contaminated food or water is an example of:
- A) Direct contact transmission
- B) Vector-borne transmission
- C) Droplet infection
- D) Vehicle-borne transmission
- Rationale: Vehicle-borne transmission involves contaminated non-living objects or substances like food and water.
- Which of these is a non-communicable disease primarily influenced by lifestyle factors?
- A) Typhoid
- B) Measles
- C) Diabetes (Type 2)
- D) Cholera
- Rationale: Type 2 Diabetes is strongly linked to diet, exercise, and other lifestyle choices, unlike infectious diseases like Typhoid, Measles, and Cholera.
- Goiter is a disease caused by the deficiency of which nutrient?
- A) Iron
- B) Vitamin A
- C) Vitamin D
- D) Iodine
- Rationale: Iodine deficiency leads to the enlargement of the thyroid gland, known as goiter.
- Which of the following is the most effective method to prevent the spread of water-borne diseases like Cholera?
- A) Using mosquito nets
- B) Ensuring access to safe and clean drinking water
- C) Regular exercise
- D) Avoiding junk food
- Rationale: Contaminated water is the primary vehicle for cholera, so safe water supply is crucial.
- Adopting a diet low in saturated fats and high in fruits and vegetables is a key preventive measure for:
- A) Tuberculosis
- B) Malaria
- C) Cardiovascular diseases
- D) Dengue
- Rationale: Diet plays a significant role in preventing non-communicable diseases like heart conditions.
- Vaccination provides immunity by stimulating the body to produce:
- A) Pathogens
- B) Toxins
- C) Antibodies
- D) Hormones
- Rationale: Vaccines train the immune system to produce antibodies against specific pathogens.
- The concept where a significant portion of a population is immune to a disease, thereby protecting unvaccinated individuals, is known as:
- A) Individual immunity
- B) Adaptive immunity
- C) Innate immunity
- D) Herd immunity
- Rationale: Herd immunity occurs when widespread vaccination reduces the spread of disease, protecting the vulnerable.
- Which vaccine is given to protect against Tuberculosis (TB)?
- A) DPT
- B) MMR
- C) BCG
- D) OPV
- Rationale: BCG (Bacillus Calmette-Guérin) vaccine is specifically for Tuberculosis.
- The Pulse Polio Immunization Program in India primarily aims to eradicate which disease?
- A) Measles
- B) Diphtheria
- C) Hepatitis B
- D) Polio
- Rationale: The Pulse Polio program is a nationwide initiative focused on eliminating polio.
