Lesson 3 of 5 / Infectious diseases in humans
Breaking the transmission chain
Which action interrupts the route a pathogen uses?
In this lesson: Explain how influenza and pneumococcus spread and how transmission can be reduced.
About 5 min
The key ideaA useful prevention explanation names the transmission route and shows exactly which part of it is interrupted.
Limit release at the source: Covering a cough or sneeze reduces release of respiratory secretions. It does not remove pathogens already inside a person or guarantee that none enter the air.
Green route: respiratory particles. Brown route: contaminated hands/contact. The barrier marks the main link affected. Dashed paths remain possible routes, not measured probabilities.
Influenza can use respiratory particles; pneumococcus spreads through respiratory secretions. Carriage can occur without obvious illness.
Explanation
Influenza viruses can spread in respiratory particles released when an infected person breathes, talks, coughs or sneezes. These can reach another person's respiratory tract. Transfer from contaminated hands or surfaces to the face can also occur, though this is less common than respiratory spread.
Pneumococcus spreads through contact with respiratory secretions such as saliva or mucus. It can live in the nose or throat without causing disease, so a carrier does not always appear ill. Transmission of a pathogen and development of disease are separate events.
Covering coughs and sneezes reduces the release of respiratory secretions. Handwashing reduces transfer from contaminated hands, and avoiding touching the face limits entry via the eyes, nose or mouth. Cleaner indoor air and reducing close contact with others while ill can reduce exposure to respiratory pathogens.
Vaccination can reduce the risk of the diseases it targets and, for some infections, reduce transmission as well. Do not claim any one measure guarantees zero infections. Match the measure to the route: safe food handling and clean drinking water address ingestion routes, whereas they do not replace measures addressing respiratory spread.
Step by step
- 1
Locate the source
Name an infected person or carrier and the secretions containing the pathogen.
- 2
Trace transfer and entry
Explain movement through respiratory particles or contaminated hands as relevant.
- 3
Interrupt a link
Show how the chosen action reduces release, exposure, transfer or entry.
Worked example
Why handwashing helps
Explain how washing contaminated hands can reduce spread of a respiratory pathogen.
One way to explain it
Handwashing removes or reduces pathogens on the hands, making transfer to another surface or to the eyes, nose or mouth less likely. It interrupts a contact route, although it does not by itself remove respiratory particles already in the air.
Why this answer works
- Name the contaminated material.
- Show the route that is interrupted.
- Avoid claiming that one action blocks every possible route.
Is this true? "Only someone visibly ill can carry a pathogen to another person."
Some infected people or carriers have no obvious symptoms. Pneumococcus can be carried in the nose or throat without causing illness.