HIV, for example, can only spread through body fluids or the like, while the common cold can travel through the air; salmonella can be transmitted through contact with food. What differences cause each virus to only be able to be transmitted in their respective forms? Why can’t they all go airborne or the like? Why are they (seemingly?) limited to only those forms of transmission?
In: Biology
It depends on what parts of the body a pathogen infects.
HIV requires white blood cells to reproduce, which is why it only spreads through what we refer to as “blood fluids” which are things like blood (obviously), semen, and breast milk. The saliva of people who have HIV does not typically contain the virus, so if someone sneezes, they’re not going to fling the virus into the air like someone with a cold would.
The common cold typically infects the sinuses and the mouth and throat, so when we cough, bacteria will spread through the air.
Salmonella infects the digestive tract, but it’s also a bacteria that tends to infect chickens. Improperly cooked chicken, and vegetables that come into contact with contaminated water will pass the bacteria on to humans. And if a human gets it, and doesn’t wash their hands properly after using the toilet, they can spread the bacteria to any food they come into contact with.
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