Notes For All Chapters – General Science Class 8
What is Health?
- Health means a state of complete physical, mental, and social well-being.
- Being healthy does not only mean the absence of disease.
- A healthy person is free from sickness and feels happy.
What is Disease?
- Disease is when the body does not work properly due to some internal or external problems.
- It causes discomfort and has specific symptoms.
- Example: Fever, cough, stomach pain, weakness.
Types of Diseases
Diseases are classified in two ways:
1. Based on Duration (Time of Disease)
| Type | Meaning | Example |
|---|---|---|
| Acute Disease | Short-term diseases, last for a few days. | Cold, Flu, Dengue |
| Chronic Disease | Long-term diseases, last for months or years. | Diabetes, Asthma, Cancer |
2. Based on Cause (Reason for Disease)
| Type | Meaning | Example |
|---|---|---|
| Hereditary Disease | Passed from parents to children. | Down’s Syndrome, Hemophilia |
| Acquired Disease | Occurs due to lifestyle, infections, or environment. | TB, Diabetes, AIDS |
3. Acquired Diseases are Further Divided Into:
| Type | Meaning | Example |
|---|---|---|
| Infectious Disease | Caused by germs, spreads from person to person. | Malaria, Flu, Cholera |
| Non-Infectious Disease | Does not spread, caused by body problems. | Heart Disease, Cancer |
Infectious Diseases
- Infectious diseases spread from one person to another.
- Caused by bacteria, viruses, fungi, protozoa, or worms.
- Spread through air, water, food, insects, or direct contact.
Table of Infectious Diseases
| Disease | Pathogen (Germ Name) | How It Spreads | Symptoms | Prevention |
|---|---|---|---|---|
| Tuberculosis (TB) | Mycobacterium tuberculosis | Air (cough, spit) | Chronic cough, blood in spit, fever | BCG Vaccine, Regular medicine |
| Hepatitis (Jaundice) | Hepatitis Virus | Contaminated water, infected needles | Yellow skin, vomiting, weakness | Drink boiled water, hygiene |
| Dysentery | Shigella bacteria, Entamoeba | Contaminated food & water | Loose motion, stomach pain | Drink boiled water, ORS |
| Cholera | Vibrio cholerae bacteria | Contaminated food & water | Vomiting, diarrhea, leg cramps | Hygiene, vaccination |
| Typhoid | Salmonella typhi bacteria | Contaminated food & water | Fever, rash, headache | Vaccination, clean drinking water |
How Diseases Spread?
1. Airborne Diseases (Spread through Air)
- Spread when a sick person coughs, sneezes, or talks.
- Example: Tuberculosis, Flu, COVID-19.
- Prevention: Wear masks, maintain distance, proper ventilation.
2. Waterborne Diseases (Spread through Water)
- Spread by drinking contaminated water.
- Example: Cholera, Typhoid, Hepatitis.
- Prevention: Drink boiled or filtered water, proper sanitation.
3. Foodborne Diseases (Spread through Food)
- Spread by eating contaminated or spoiled food.
- Example: Food poisoning, Dysentery.
- Prevention: Eat fresh, properly cooked food, wash hands.
4. Vector-Borne Diseases (Spread by Insects & Animals)
| Disease | Spread By |
|---|---|
| Malaria | Female Anopheles mosquito |
| Dengue | Aedes mosquito |
| Plague | Rats & fleas |
| Rabies | Dog bite |
| Swine Flu | Infected pigs & humans |
- Prevention: Use mosquito nets, avoid animal bites, get vaccines.
5. Direct Contact Diseases (Spread through Touch)
- Spread by touching infected people or objects.
- Example: Ringworm, Scabies, Skin infections.
- Prevention: Wash hands regularly, avoid sharing clothes.
Some Important Diseases
1. Dengue (Spread by Aedes Mosquito)
- Cause: Dengue Virus.
- Symptoms: High fever, headache, joint pain, low platelet count.
- Prevention: Remove stagnant water, use mosquito repellents.
2. Swine Flu (Spread through Nose & Mouth Secretions)
- Cause: H1N1 Influenza Virus.
- Symptoms: Fever, body pain, sore throat, breathing problems.
- Prevention: Cover nose while sneezing, avoid crowded places.
3. AIDS (Acquired Immunodeficiency Syndrome)
- Cause: HIV Virus (Human Immunodeficiency Virus).
- Symptoms: Weak immune system, frequent infections.
- Spread By: Unsafe sex, infected blood transfusion, sharing needles.
- Prevention: Safe medical practices, awareness about HIV.
4. Rabies (Spread by Animal Bite)
- Cause: Rabies Virus.
- Symptoms: Fear of water, fever, excessive saliva, brain infection.
- Prevention: Immediate vaccine after an animal bite.
Non-Infectious Diseases
- Do not spread from person to person.
- Caused by genetic problems, lifestyle, or environmental factors.
1. Cancer (Uncontrolled Growth of Body Cells)
- Causes: Smoking, tobacco, unhealthy diet, pollution.
- Symptoms: Swelling, weight loss, constant pain.
- Prevention: Avoid smoking, eat healthy, exercise.
2. Diabetes (High Blood Sugar Level)
- Cause: Low insulin production in the body.
- Symptoms: Frequent urination, weight loss, weakness.
- Prevention: Healthy diet, regular exercise, no junk food.
3. Heart Diseases (Blocked Blood Flow to Heart)
- Causes: Obesity, high cholesterol, smoking, stress.
- Symptoms: Chest pain, breathlessness, sweating.
- Prevention: Exercise daily, eat healthy, avoid smoking.
Importance of Hygiene and Healthy Lifestyle
✔ Personal Hygiene: Bath daily, wash hands, wear clean clothes.
✔ Clean Surroundings: No garbage, no stagnant water to stop mosquito breeding.
✔ Healthy Food: Eat fresh, balanced food with vitamins and minerals.
✔ Exercise & Yoga: Helps in reducing stress and prevents diseases.
✔ Vaccination: Protects against infectious diseases like polio, measles, hepatitis.
Leave a Reply