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Class XII Biology · Chapter 7

Human Health& Disease

A comprehensive study guide covering infectious diseases, pathogens, transmission routes, and prevention strategies.

8
Diseases
5
Pathogen Types
4
Transmission Routes
10+
Quiz Questions
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01

Types of Pathogens

🦠
Bacteria
Salmonella, Streptococcus
🧬
Viruses
Rhino virus, HIV
🍄
Fungi
Microsporum, Trichophyton
🔬
Protozoans
Plasmodium, Entamoeba
🪱
Helminths
Ascaris, Wuchereria
02

Infectious Diseases

🔍
🌡️
Bacteria
Typhoid Fever
Salmonella typhi
Symptoms
39–40°C FeverWeaknessStomach PainConstipationHeadacheIntestinal Perforation
Transmission
Contaminated WaterContaminated FoodFaecal-Oral Route
💡 Confirmed by Widal Test. Famous carrier: Mary Mallon ("Typhoid Mary")
🫁
Bacteria
Pneumonia
Streptococcus pneumoniae · Haemophilus influenzae
Symptoms
Fever & ChillsCoughHeadacheCyanosis (bluish lips)
Transmission
Droplets/AerosolsShared Utensils
⚠️ Infects the alveoli — fills them with fluid, blocking gas exchange.
🤧
Virus
Common Cold
Rhino viruses
Symptoms (3–7 days)
Nasal CongestionSore ThroatHoarsenessCoughTiredness
Transmission
DropletsFomites
🔑 Affects nose & respiratory passage — NOT the lungs.
🦟
Protozoan
Malaria
Plasmodium vivax · P. malariae · P. falciparum
Symptoms
Recurring FeverChills (every 3–4 days)P. falciparum — Fatal
Transmission
Female Anopheles Mosquito
🔬 Haemozoin from burst RBCs causes recurring fever & chills.
🦠
Protozoan
Amoebiasis
Entamoeba histolytica
Symptoms
ConstipationAbdominal CrampsBlood & Mucous in Stools
Transmission
Contaminated Food/WaterHouseflies (Mechanical Carrier)
🪰 Houseflies = mechanical carriers.
🪱
Helminth
Ascariasis
Ascaris lumbricoides (Roundworm)
Symptoms
Internal BleedingMuscular PainFever & AnaemiaIntestinal Blockage
Transmission
Contaminated Water/VegetablesContaminated Soil
🥦 Eggs contaminate soil, water, vegetables, and fruits.
🦵
Helminth
Filariasis
Wuchereria bancrofti · W. malayi
Symptoms
Chronic InflammationMassive Limb SwellingGenital Deformities
Transmission
Female Culex Mosquito
🐘 Also called Elephantiasis. Worms live in lymphatic vessels for many years.
🍄
Fungi
Ringworm
Microsporum · Trichophyton · Epidermophyton
Symptoms
Dry Scaly LesionsIntense ItchingAffects Skin/Nails/Scalp
Transmission
Soil ContactShared Towels/Combs/Clothes
☀️ Heat & moisture promote growth. NOT caused by worms!
03

Prevention & Control

🧼
Personal Hygiene
  • Keep body clean daily
  • Drink clean/boiled water
  • Wash fruits and vegetables
  • Avoid sharing personal items
  • Wash hands before meals
🏙️
Public Hygiene
  • Proper disposal of waste & excreta
  • Disinfect water reservoirs & pools
  • Hygiene standards in public catering
  • Periodic cleaning of tanks & cesspools
🦟
Vector Control
  • Avoid water stagnation near homes
  • Clean household coolers regularly
  • Use mosquito nets & repellents
  • Introduce Gambusia fish in ponds
  • Spray insecticides in drainage areas
  • Install wire mesh on doors & windows
💉
Vaccines & Medicine
  • Smallpox — completely eradicated
  • Polio, Diphtheria — largely controlled
  • Pneumonia, Tetanus — vaccines available
  • Antibiotics for bacterial infections
  • Biotechnology → newer safer vaccines
04

Quick Reference

DiseasePathogenTypeOrganTransmissionKey Symptom
TyphoidSalmonella typhiBacteriaSmall intestineContaminated food/waterSustained high fever
PneumoniaStreptococcus pneumoniaeBacteriaLungs (Alveoli)Droplets, shared utensilsCyanosis
Common ColdRhino virusesVirusNose, respiratory passageDroplets, fomitesNasal congestion
MalariaPlasmodium spp.ProtozoanLiver, RBCsFemale AnophelesRecurring fever
AmoebiasisEntamoeba histolyticaProtozoanLarge intestineFood/water, housefliesBlood in stools
AscariasisAscarisHelminthIntestineFood/water/soilIntestinal blockage
FilariasisWuchereria bancroftiHelminthLymphatic vesselsFemale CulexLimb swelling
RingwormMicrosporum, TrichophytonFungiSkin, nails, scalpSoil, shared itemsScaly lesions, itching
05

Test Your Knowledge

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