IP Biology Notes: Infectious Diseases in Humans (Upper Sec 09)

For Integrated Programme students: Your current school materials, teacher instructions, and assessment scope take precedence because IP topic sequence and depth vary by school. This is an Eclat IP guide, not the O-Level / SEC G3 exam-track guide.

How this chapter applies

• Eclat core: infectious versus non-infectious disease, bacterial and viral pathogens, transmission, influenza, pneumococcal disease, vaccination, antibiotics, and resistance form the main route.
• School-sensitive extension: detailed clonal selection, named immune-cell pathways, epidemiological modelling, and wider pathogen case studies should be used only where the current school teaches them.
• 2027 national comparison: K325 Topic B9 explicitly focuses on influenza virus, pneumococcus, transmission controls, vaccine response, antibiotic targets, and selection for resistance.
• Check your school: case studies, immunity terminology, and the amount of molecular detail expected for antibiotics or viruses can differ.
• Exam-track route: use the separate O-Level and SEC G3 Biology notes for K325 topic ownership.

The core idea is simple: Infectious disease answers must link pathogen, route, defence, and control.

Use it as a working check: Match each prevention method to the transmission route. Antibiotics work on bacteria, not viruses, and misuse selects resistant bacteria.

Then go one layer deeper: Example: masks and isolation help droplet spread, while clean water and proper cooking help food or water spread. Vector control fits mosquito-borne disease.

What you must know

• Infectious diseases caused by pathogens (viruses, bacteria); non-infectious include genetic, lifestyle diseases.
• Virus vs bacteria: viruses are acellular, need host to replicate; bacteria are cells with cytoplasm, membrane, wall, sometimes plasmids.
• Case studies: influenza (droplet spread, fever, body aches), pneumococcal disease (bacterial, can cause pneumonia/meningitis); both preventable by vaccines, hygiene, masks, reducing crowding.
• Immunity: vaccines introduce antigens to stimulate memory cells/antibodies without causing disease.
• Antibiotics kill or inhibit susceptible bacteria, not viruses. Misuse and overuse increase selection for resistant strains. Follow the prescribed dose and duration rather than stopping, extending, or sharing treatment without clinical advice.

Detailed notes

• Transmission: droplets, contact, contaminated food/water, vectors (mosquitoes), body fluids. Break chain with hygiene, clean water, cooking, masks, isolation, vector control (remove stagnant water, nets, insecticides).