Diseases: Cause And Control Chapter Notes | Home Management for SSS 2 PDF Download

What is a Disease?

• A condition that disrupts the body's normal functioning.
• Can be mild and curable or severe and potentially fatal.
• Defined as a structural or functional disorder of the body.
• Early beliefs attributed diseases to supernatural causes like gods or evil spirits, treated with magic or sorcery.
• Modern science identifies specific causes for diseases, enabling prevention and treatment.
• World Health Day is celebrated on April 7 to promote health awareness.

Categories of Diseases

• Extent of occurrence: Endemic, epidemic, pandemic, sporadic.
• Communicability: Infectious (caused by germs) or non-infectious (due to bodily dysfunction).
• Type of pathogen: Bacterial, viral, protozoan, or others.
• Mode of transmission: Water-borne, food-borne, air-borne, or insect-borne.

Categories of Diseases Based on Extent of Occurrence

• Endemic: Limited to a specific area, affecting fewer people (e.g., yellow fever in some African countries, goitre in sub-Himalayan regions).
• Epidemic: Spreads rapidly across places, affecting many people (e.g., plague in India in 1994).
• Pandemic: Widespread globally (e.g., AIDS).
• Sporadic: Scattered individual cases (e.g., malaria, cholera).

Categories of Diseases Based on Communicability

Non-Communicable or Non-Infectious Diseases

• Not caused by germs and cannot spread from person to person.
• Examples: Diabetes, colour blindness, heart attack, beri-beri.

Communicable or Infectious Diseases

• Caused by pathogens (disease-causing organisms).
• Spread from one person to another through infection.
• Incubation period: Time between pathogen entry and symptom appearance (varies from hours to days).
• Examples: Cholera, smallpox, malaria.

Non-Infectious Diseases

• Nutritional deficiency: Beri-beri, scurvy, goitre, kwashiorkor, night-blindness.
• Metabolic: Diabetes mellitus, goitre (hyperthyroidism).
• Genetic: Haemophilia, thalassemia.
• Allergies: Hay fever, asthma.
• Degenerative (ageing): Arthritis, cataract.
• Physical and chemical causes: Injury, heat, cold, radiation, poisoning.
• Mental illness: Depression, schizophrenia.
• Cancer: Breast cancer, prostate cancer, leukemia.
• Cancer involves abnormal cell multiplication, potentially forming tumors, often fatal if untreated.
• Causes of cancer include chemicals, tobacco, pollution, radiation, and certain viruses (carcinogens).
• Cancer commonly affects tissues with active cell division (e.g., skin, liver, stomach, uterus, breasts).

Communicable or Infectious Diseases

• Caused by pathogens like bacteria, viruses, protozoa, or helminths.
• Bacterial: Cholera, typhoid, tuberculosis.
• Viral: AIDS, chicken pox, hepatitis.
• Protozoan: Malaria, amoebic dysentery, sleeping sickness.
• Helminthic: Ascariasis, taeniasis, filariasis.
• Incubation periods vary (e.g., pneumonia: 1-3 days; AIDS: up to 12+ years).

Incubation period of some diseases

Diseases Caused by Bacteria

Cholera

• Caused by Vibrio cholerae bacterium.
• Incubation period: Few hours to 6 days.
• Attacks the intestinal tract.
• Symptoms: Vomiting, severe diarrhea, dehydration, reduced urination, urea accumulation (toxic if untreated).
• Transmission: Contaminated food and water (faeco-oral route), spread by flies carrying germs from excreta.
• Prevention: Good sanitation, fly control, covering food, boiling drinking water, eating cooked food, anti-cholera vaccination.
• Treatment: Saline water injections to restore body fluids.

Typhoid Fever

• Caused by Salmonella typhi bacterium.
• Incubation period: 7-21 days.
• Attacks the intestines.
• Symptoms: Continuous fever (higher in afternoons), reddish eruptions on chest and abdomen, headache, diarrhea.
• Transmission: Contaminated water, milk, or food; spread by flies.
• Prevention: Proper sanitation, anti-typhoid vaccination.

Tuberculosis

• Caused by Mycobacterium tuberculosis bacterium.
• Incubation period: 2-10 weeks.
• Symptoms: Persistent cough, afternoon fever, bloody mucus, weight loss, fatigue, chest pain, breathlessness.
• Transmission: Air, dust, or sputum from infected person.
• Prevention: BCG vaccination, patient isolation.

Diseases Caused by Protozoa

Malaria

• Caused by Plasmodium protozoan.
• Incubation period: About 3 weeks.
• Symptoms: Chills, high fever recurring every 3-4 days.
• Transmission: Bite of female Anopheles mosquito.
• Parasite multiplies in red blood cells, destroying them.
• Prevention: Mosquito control (destroying breeding sites), using mosquito nets or repellents.
• Treatment: Drugs like quinine, paludrin, camoquin.

Amoebic Dysentery (Amoebiasis)

• Caused by Entamoeba histolytica protozoan.
• Incubation period: About 1 week.
• Symptoms: Diarrhea, griping pain, mucus or blood in stools, damage to large intestine lining.
• Transmission: Contaminated food, especially via flies.
• Prevention: Proper sanitation, protecting food from dust and flies.

Sleeping Sickness

• Caused by Trypanosoma brucei gambiense or rhodesiense protozoan.
• Symptoms: First phase: Fever, headache, itchiness, joint pains; Neurological phase: Confusion, poor coordination, numbness, sleep disturbances (potentially fatal).
• Transmission: Bite of Tsetse fly.
• Treatment: Drugs like metarsophol.

Diseases Caused by Parasitic Worms

Ascariasis

• Caused by roundworm (Ascaris lumbricoides).
• Worms live in intestines, absorbing host’s digested food.
• Symptoms: Weakness due to nutrient loss.
• Transmission: Eggs in patient’s feces contaminate soil, vegetables, or hands; spread through unwashed hands or raw vegetables.
• Female worms lay thousands of eggs daily.

Taeniasis

• Caused by tapeworm (Taenia solium).
• Worms live in intestines, absorbing host’s food, causing weakness.
• Transmission: Eating raw or undercooked pork or beef containing larval stages.
• Eggs in feces contaminate animals; humans infected by consuming infected meat.

Filariasis (Elephantiasis)

• Caused by filarial worm (Wuchereria bancrofti).
• Symptoms: Swollen limbs/ankles, fever, chills, inflamed lymph glands/vessels.
• Transmission: Bite of Culex mosquito.
• Worms block lymphatic system, causing swelling.
• Treatment: Mosquito eradication, antibiotics, anti-inflammatory analgesics.

Viral Diseases

What are Viruses?

• Extremely small, made of nucleic acids and proteins, visible only under electron microscope.
• Cannot live freely; survive inside host cells.
• Take over host cell metabolism to produce more viruses, often killing the host cell.
• Highly specific, attacking specific hosts and tissues.
• Can be cultured in labs or crystallized for storage.

Common Viral Diseases

1. HIV/AIDS

• First identified in the USA in 1981, AIDS has spread globally, with over 2 million confirmed cases in India alone. This incurable, nearly always fatal disease, with no vaccine available, primarily affects people aged 20–39. AIDS is the final stage of HIV infection, caused by the HIV virus, which is found in body fluids like blood, semen, saliva, tears, and urine. 
• It weakens the immune system, making patients vulnerable to minor infections and cancers. The incubation period can exceed 10–12 years, during which HIV-positive individuals may remain asymptomatic. Once AIDS develops, death often occurs within three years due to secondary infections or cancers. Symptoms include swollen lymph nodes, fever, night sweats, and weight loss.

Transmission: HIV spreads through:

• Sexual intercourse (heterosexual or homosexual, especially anal sex) with an infected person; prostitution is a major source.
• Contaminated blood transfusions, particularly in cases like thalassemia, where frequent transfusions increase risk (e.g., a 1995 report noted 45 of 64 thalassemia children in a Mumbai hospital were HIV-positive due to transfusions).
• Mother-to-child transmission via the placenta.
• Shared injection needles, common among drug abusers. Disposable syringes are now used in hospitals to prevent this.

2. Chicken Pox: Caused by the Varicella Zoster virus (a herpes virus), this highly contagious disease mainly affects children but can also occur in adults. It spreads through close contact with an infected person. Symptoms include itchy rashes starting on the chest and back, spreading to the arms, legs, face, and head. These rashes begin as pink spots, turn into watery blisters, and later form scabs, which is the infectious period.

Treatment: Bed rest, keeping rashes clean and dry, avoiding scratching blisters, and applying calamine lotion or neem leaves to reduce itching. A live attenuated varicella vaccine is recommended for children aged 12–18 months for active immunization.

3. Hepatitis: Caused by five viral strains (Hepatitis A, B, C, D, and E), this disease inflames the liver and spreads through contaminated food, water, syringes, or blood transfusions.

• Hepatitis A: Incubation period of 14–45 days, common in children and young adults, primarily transmitted via contaminated food or water.
• Hepatitis B: Incubation period of 6–26 weeks, affects all ages, spreads through contaminated syringes or transfusions, and may lead to liver cirrhosis or cancer.
• Hepatitis C and D: Similar to B in transmission and liver damage.
• Hepatitis E: Also transmitted through contaminated food or water.

  Symptoms include fever, headache, joint pain, loss of appetite, nausea, vomiting, and, after 3–10 days, jaundice with dark yellow urine and light-colored stools.

Treatment: Bed rest until fever subsides, a high-calorie diet with minimal protein and fat, and strict hygiene (e.g., washing hands after handling the patient’s bedpan or clothes).

Differences Between Viruses and Bacteria

Viruses:

• Very small, visible only under an electron microscope.
• Non-cellular, lack metabolism, and cannot take food.
• Do not grow or divide; can be crystallized.
• Hijack host cells to replicate.
• All cause diseases in humans, animals, or plants.

Bacteria:

• Larger, visible under a light microscope.
• Single-celled with metabolism, absorb food.
• Grow and divide to reproduce.
• Cannot be crystallized; self-reproduce.
• Some are harmless, some beneficial, and some cause diseases.

Points to Remember

• Disease disrupts normal body functioning.
• Classified by occurrence (endemic, epidemic, pandemic, sporadic), communicability (infectious, non-infectious), pathogen type, and transmission mode.
• Incubation period is the time from pathogen entry to symptom appearance.
• Bacterial diseases: Tuberculosis, cholera, typhoid.
• Viral diseases: AIDS, chicken pox, hepatitis.
• Roundworm and tapeworm diseases spread through contaminated food.
• AIDS (HIV) weakens the immune system, making patients vulnerable to infections.