Exam Tips: Pathogens and Disease Transmission

Always give a named example: When identifying a pathogen type, give a specific disease name. "Bacteria cause TB" is far stronger than "bacteria cause diseases." Named examples earn marks; vague statements do not.

Transmission needs mechanism, not just route: Saying "measles spreads by air" is incomplete. Say "an infected person coughs or sneezes, releasing droplets containing the virus into the air; a healthy person inhales these droplets and the virus enters their respiratory tract." That level of detail earns full marks.

Antibiotics and viruses — know the exact reason: Antibiotics work by targeting structures unique to bacteria — typically the cell wall or bacterial ribosomes. Viruses do not have cell walls or ribosomes of their own. Therefore, antibiotics have no target in a virus and cannot harm it. This distinction is worth 1-2 marks in almost every paper.

Prevention must match transmission: Each transmission route has a specific prevention strategy. Airborne: masks/ventilation. Vector: nets/insecticides. Water: filtration/chlorination. Food: cooking/refrigeration. Linking these correctly shows understanding, not just recall.

Practical safety: why 25°C not 37°C: Culturing bacteria at body temperature (37°C) could allow harmful human pathogens to grow to dangerous levels. School experiments use 25°C to reduce this risk. This is a very common exam question — memorise the reason, not just the temperature.

Malaria detail for higher marks: For 4-5 mark questions on malaria, include: (1) pathogen type (Plasmodium, a protist), (2) vector (female Anopheles mosquito), (3) mechanism (mosquito injects Plasmodium into bloodstream when biting), (4) where Plasmodium reproduces (in red blood cells and liver cells), (5) control strategies (nets, draining stagnant water, antimalarial drugs).