Why is flu more prevalent in winter?

Why is flu more prevalent in winter?

we think flu spreads better in winter because of human behaviour because it does this reproducibly in every country in the world and in which it is winter time - it doesn’t mean it goes away completely in summer but it does come much more commonly in winter.

We think that’s because it spreads better in winter because of what humans do. We go indoors more in winter so there are more people together indoors with the windows closed. Also, unlike summer time, it’s less light and therefore there's less ultraviolet radiation to dry out the virus and kill it. So 'flu finds it easier to persist on surfaces spread by coughs and sneezes, and it hangs around for longer.

As a result you have a higher chance of passing it on so that’s what we think goes on. And then the big determinant, the disproportionate determinant, is the school year. The long summer school holiday powerfully knocks 'flu on the head because kids stop mixing and spreading the infection amongst themselves. What normally happens is that they become infected and then go home and give it to their parents and the parents then carry the infection to all of the other parts of the social and age strata, usually through their workplace.

How does 'flu actually infect our cells?

How does 'flu actually infect our cells?

The way flu gets hold of cells is down to proteins on the surface of the virus particle. Each virus particle is tiny, about 1/10,000th for the millimetre across. If you could zoom in on the surface, you’d see that it had these spikes on the surface. These spikes are a structure called haemagglutinin, which is a tiny protein resembling a molecular grappling hook. It’s viral Velcro. It gets hold of something called sialic acid, which is a chemical on the surface of the cells that line our nose and throat, and this enables the virus to grab hold of those cells and pull itself in very close.

Through this interaction the cell thinks the virus is something that it has to take inside the cell. So the cell then does something called receptor-mediated endocytosis, which basically means it pulls the virus inside the cell. Once inside the virus releases it’s genetic material and productively infects the cell.

It’s a bit like a Trojan horse actually because the Trojan horse was this juicy tidbit sitting outside the gate of Troy. The guys inside the city thought, “Wow! That looks fantastic. We’ll pull that inside because it looks good.” And it goes inside the city. And then of course, lurking inside are all these people who are then wreak havoc inside the city. And that’s basically what a flu virus does. It hijacks the cell, turns it into a virus factory and then it infects all of the cells around it and all the people around you!