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Communicable diseases are caused by pathogens and can spread between hosts. Bacteria may produce toxins or damage tissue; viruses reproduce inside host cells. Fungi and protists cause other diseases. Examples must match the board specification: measles is viral, salmonella bacterial, malaria a protist disease and rose black spot fungal. Prevention targets the transmission route, such as vaccination, hygiene, vector control or barriers, rather than assuming one method prevents every infection.
Video by Cognito. The video’s own board label is retained; follow the specification reference and scope notes on this lesson for assessed content.
Viewing focus: Compare pathogen types and transmission
After watching, attempt these questions before opening the answers. You can also use the written lesson below.
After watching 1: What do antibodies recognise?
Specific antigens. Their binding sites match particular antigens.
After watching 2: What type of pathogen causes malaria?
A protist. Mosquitoes can transmit the parasite.
What you'll be able to do
Communicable diseases are caused by pathogens and can spread between hosts. Bacteria may produce toxins or damage tissue; viruses reproduce inside host cells. Fungi and protists cause other diseases. Examples must match the board specification: measles is viral, salmonella bacterial, malaria a protist disease and rose black spot fungal. Prevention targets the transmission route, such as vaccination, hygiene, vector control or barriers, rather than assuming one method prevents every infection.
Skin and mucus provide barriers; stomach acid destroys many swallowed pathogens. White blood cells can engulf pathogens, produce antibodies matching particular antigens, and produce antitoxins. Vaccination introduces suitable antigens so immune memory develops without the full disease risk. A later response is faster and more effective. Population protection depends on transmission, coverage and the disease; vaccination does not mean every individual can never be infected.
Antibiotics act against susceptible bacteria, not viruses. Resistant variants may survive treatment and reproduce, so antibiotic use creates selection pressure rather than instructing bacteria to mutate on demand. New drugs undergo preclinical and clinical testing for toxicity, dose and effectiveness. Placebos, random allocation and blinding reduce bias where appropriate. Compare outcomes and side effects using data; an anecdote is weaker evidence than a well-controlled trial.
Attempt these problems on paper before opening the worked reasoning. Explain your steps as well as giving a final answer.
Common mistakes to avoid
Key takeaways
Question 1: How does random allocation help a drug trial?
It reduces allocation bias and confounding.
Check the assessed scope and practical or mathematical requirements.
An external explanation or interactive activity to use alongside the lesson. It may include extension material.
Close the notes and answer from memory. Revisit any explanation you cannot yet reconstruct.
Test yourself
Answer a few questions, then review anything you missed.
Start with the quiz above to check the key ideas. You can also choose another topic from the practice library.