[Lewis Thomson (OP)]

Jonathan has been wondering about the following for a while now and would like some help finding answers.

"From the start of the pandemic I was paying particular attention to the details around Covid 19, how it spreads, how it will affect you and most of all how to protect yourself and others around you. Especially since my father was discharged from hospital after having major lung surgery several days before the first lockdown.

The biggest problem with Covid was the huge number of asymptomatic infected people, not even knowing they were spreading it. My question to you is: how does this compare with Flu, Noravirus, the common cold and other common respiratory viruses? Are there asymptomatic carriers of these viruses too?"

Can you help them? Leave your answers in the comments below...

[set fair]

Are there asymptomatic carriers of these viruses too?"[/i]

There are certainly plenty of viruses which you can catch without you ever knowing you're infected. Our bodies contain trillions of viral particles. It is an advantage for a respiratory virus to cause you to cough or sneeze, it helps it to spread. Making us so ill that we take to our beds is a distinct disadvantage. It's not uncommon (but neither is it common) for respiratory viruses to inhibit the interferon response well enough that you don't get that early warning of feeling vaguely ill, which tells you that a cold is on the way, but Covid is particularly good at this - it has about 14 proteins which mess with interferon and one which gets the nucleus to inhibit presenting (on the cell surface) cut up bits of protein produced in the cell, which would alert white blood cells that it is infected.

Sorry I can't be more specific about how common it is, I don't think they've done enough investigating to know, viroligists are not so interested in infections which don't make you ill or ones that make you mildly symtomatic. I expect the vast majority of people cough, snivel or sneeze at least onve every week. If we feel a bit tired one day we don't think much about it.