The idea of respiratory viruses not being airborne sounds silly. What's the viral charge supposed to do, not jump into droplets smaller than certain size?
Of course they are present in the smallest droplets! They are present in the mucous secretions of the infected individual and they will get expelled through the big and the small droplets.
The distinction shouldn't be a qualitative one, airborne vs not airborne. It's a quantitative one, sufficiently infectious viruses may pose a risk at much smaller doses, the kind that you may be exposed by the smallest droplets expelled that simply stay afloat.
It's also worth noting that human immune response is a complicated beast, what may not be infectious for an average healthy individual may put down someone with a weakened immune response. So even supposedly "not airborne" viruses that are very unlikely to infect the average healthy individual at very small doses may pose an "airborne" risk for individuals with a weakened immune response.
There are more factors in all of this, atmospheric conditions may play a role. For example, cold temperatures may be more suitable for the virus to remain infectious outside of a host, thus increasing the likelihood of "airborne" propagation.
TL;DR: The distinction between airborne and not airborne viruses is an artificial one. That only makes sense statistically for an average individual at certain atmospheric conditions for a concrete strain of the virus. But as any real-world statistical distribution there are tails and you will find "airborne" qualities for pretty much any respiratory virus in those tails.
Of course they are present in the smallest droplets! They are present in the mucous secretions of the infected individual and they will get expelled through the big and the small droplets.
The distinction shouldn't be a qualitative one, airborne vs not airborne. It's a quantitative one, sufficiently infectious viruses may pose a risk at much smaller doses, the kind that you may be exposed by the smallest droplets expelled that simply stay afloat.
It's also worth noting that human immune response is a complicated beast, what may not be infectious for an average healthy individual may put down someone with a weakened immune response. So even supposedly "not airborne" viruses that are very unlikely to infect the average healthy individual at very small doses may pose an "airborne" risk for individuals with a weakened immune response.
There are more factors in all of this, atmospheric conditions may play a role. For example, cold temperatures may be more suitable for the virus to remain infectious outside of a host, thus increasing the likelihood of "airborne" propagation.
TL;DR: The distinction between airborne and not airborne viruses is an artificial one. That only makes sense statistically for an average individual at certain atmospheric conditions for a concrete strain of the virus. But as any real-world statistical distribution there are tails and you will find "airborne" qualities for pretty much any respiratory virus in those tails.
reply