5.5 - 5.6 - Infection spread
Connect each named infection to its pathogen, its effects and its transmission route. Use those links to explain why a particular prevention measure interrupts spread, and why HIV damage can make other infections more likely.
5.5–5.6 · Breaking waterborne and airborne routes
An infection spreads only if a pathogen can leave one source, travel by a suitable transmission route, and reach a new host. A control measure works when it interrupts one of those steps. This is why the best control depends on the route: treating drinking water will not stop an airborne infection, while ventilation will not make contaminated water safe.
| Infection | Pathogen and effect | How it spreads | How spread can be reduced, and why |
|---|---|---|---|
| Cholera | A bacterium causes diarrhoea. | Faeces containing cholera bacteria can contaminate water. A new person becomes infected when they consume the contaminated water. | Treating or boiling drinking water kills the bacteria; safe sanitation keeps infected faeces out of water supplies; handwashing reduces transfer into food or water. |
| Tuberculosis (TB) | A bacterium usually infects and damages the lungs. | A person with infectious TB releases bacteria in airborne particles when coughing, sneezing or spitting. Another person can inhale those particles. | Covering coughs and using suitable masks reduce release or inhalation; good ventilation removes and dilutes infectious particles; identifying and treating infected people reduces the source of bacteria. |
| Chalara ash dieback | A fungus causes premature leaf loss and bark lesions in ash trees. | Spores released from infected leaf material are carried through the air by wind to other ash trees. Infected plants can also carry the fungus over longer distances. | Destroying, burying or deep-composting infected fallen leaves reduces the source of spores. Restricting movement of infected ash plants and cleaning plant debris from footwear and wheels reduce human-assisted spread. Windborne spread cannot be stopped completely. |
The disease effect and the route are different facts. Diarrhoea is an effect of cholera; contaminated water is its route. Leaf loss is an effect of Chalara ash dieback; windborne fungal spores are its route.
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