Biology Diseases - Quick Revision
Biology Diseases - Quick Revision
Key Points (One-Liners)
- Bacteria cause TB (Mycobacterium), Cholera (Vibrio), Typhoid (Salmonella).
- Viruses cause AIDS (HIV), Measles (RNA virus), Rabies (RNA virus), COVID-19 (SARS-CoV-2).
- Protozoa cause Malaria (Plasmodium), Amoebiasis (Entamoeba), Sleeping sickness (Trypanosoma).
- Fungi cause Ringworm & Athlete’s foot; no chlorophyll, keratin feeders.
- Helminths cause Elephantiasis (Wuchereria), Taeniasis (Tapeworm).
- Vector: Female Anopheles → Malaria; Aedes → Dengue/Chikungunya; Culex → Filariasis.
- VAC vaccine: DPT (Diphtheria, Pertussis, Tetanus) + Polio drops + BCG (TB).
- Hepatitis-B vaccine is first recombinant DNA vaccine approved for humans.
- Antibiotics work only on bacteria (penicillin inhibits cell-wall); useless vs viruses.
- Passive immunity: Ready-made antibodies (mother’s milk, antiserum); short-term.
- Active immunity: Body makes its own antibodies (infection/vaccine); long-term.
- SCID “bubble boy” disease—gene therapy first success using retrovirus vector.
- Koch’s postulates 4-step proof to confirm pathogen-disease link.
- Incubation period: Time b/w entry & first symptom; infectivity may precede symptoms.
- One Health concept: Human-animal-environment interface to curb zoonoses (e.g., Nipah).
| Formula/Rule |
Application |
| Basic Reproduction Number R₀ = (β × c × D) |
Predict epidemic spread; R₀ < 1 → disease dies out. |
| Herd immunity threshold % = 1 – 1/R₀ |
Estimate minimum vaccination coverage needed. |
| Attributable Risk = Iₑ – Iᵤ |
Extra risk due to exposure (Iₑ = incidence in exposed, Iᵤ = unexposed). |
| Case-Fatality Rate = (Deaths ÷ Cases) × 100 |
Gauge virulence; higher → deadlier disease. |
| Odds Ratio (OR) = (a×d)/(b×c) |
Case-control studies; OR > 1 → risk factor. |
| Incidence = (New cases ÷ Population at risk) × 1000 |
Fresh disease load per 1000 per year. |
| Prevalence = Incidence × Duration |
Total existing cases; longer chronicity → higher prevalence. |
| Vaccine Efficacy = (ARU – ARV)/ARU × 100 |
% reduction in attack rate (ARU unvaccinated, ARV vaccinated). |
| Doubling Time ≈ 70 ÷ growth rate % |
Estimate how fast cases double in outbreak. |
Memory Tricks
- “VAMP” – Viruses: AIDS, Measles, Polio (all RNA except smallpox DNA).
- “BCTV” – Bacterial diseases: B-Botulism, C-Cholera, T-Tetanus, V-Typhoid.
- “MANGO” – Malaria, Amoebiasis, Nagana, Giardiasis, Organisms = Protozoa.
- “Very Sick People Take Medicine” – Vibrio, Salmonella, Plasmodium, Trypanosoma, Mycobacterium (causative germs).
- Ring-shaped rash → think “FUN-guy” (Fungi) with RING on finger.
Common Mistakes
| Mistake |
Correct Approach |
| Using antibiotics for common cold (viral) |
Antibiotics only for bacterial infections; symptomatic care for viral. |
| Confusing vector & pathogen |
Mosquito = vector; Plasmodium = pathogen. |
| Saying TB vaccine gives lifelong immunity |
BCG protects only severe childhood forms; adults still at risk. |
| Ignoring incubation period while judging negative test |
Wait full incubation before ruling out infection (e.g., 2–12 weeks HIV). |
| Marking Hepatitis-B as water-borne |
It’s blood/body-fluid borne; Hep-A & E are water-borne. |
Last Minute Tips
- 30-sec rule: Glance name → causative agent → vector → vaccine; rapid recall chain.
- Draw two columns: Bacterial vs Viral → list top 5 diseases each; visual contrast sticks.
- Remember 3 “F”: Fungi = Feet & Flaky skin (superficial); deep only in immuno-compromised.
- Watch double negatives in MCQs: “Which is NOT matched” → pick odd one out.
- First 30 min of exam: Attempt all disease questions; they are factual & quick scoring.
Quick Practice (5 MCQs)
1. Which of the following is NOT a viral disease?
A) Rabies B) Measles C) Tetanus D) Mumps
**Answer:** C) Tetanus (bacterial)
2. Match the pair correctly:
a) Kala-azar 1) Wuchereria
b) Sleeping sickness 2) Leishmania
c) Filariasis 3) Trypanosoma
A) a-2, b-3, c-1 B) a-3, b-2, c-1 C) a-1, b-2, c-3 D) a-2, b-1, c-3
**Answer:** A
3. The vaccine for which disease is included under Universal Immunization but does NOT target a virus?
A) Polio B) DPT C) Hep-B D) Rotavirus
**Answer:** B) DPT (Diphtheria, Pertussis, Tetanus – all bacterial)
4. Which vector is responsible for transmitting both Dengue and Chikungunya?
A) Anopheles B) Culex C) Aedes D) Glossina
**Answer:** C) Aedes
5. If R₀ of a new infection is 4, the minimum percentage of population to vaccinate to stop spread is:
A) 25% B) 50% C) 75% D) 90%
**Answer:** C) 75% (HIT = 1 – ¼ = 0.75)
BETA
