"After lockdown, immune system reacts more strongly to viruses and bacteria." ScienceDaily. ScienceDaily, 18 December 2024. <www.sciencedaily.com / releases / 2024 / 12 / 241218174922.htm>.

Viruses, on the other hand, are bits of genetic information – either RNA or DNA – surrounded by protein. A virus always needs a living host to survive, like a human body or an animal.

For the bacterial species that inhabit your gut, there's a frenzy of viruses called bacteriophages that naturally infect them. Although they co-evolved with bacteria, phages get far less glory.

If everyone you know is falling victim to illness this season, there’s any number of widely circulating viruses – or even bacteria – that could be to blame.