What happens when flu meets Covid-19?

How seasonal viruses interact with the coronavirus is unknown - it may lessen or sharpen the pandemic - so flu vaccinations are vital

Optimists had hoped Covid-19 might not withstand the blistering heat of a British summer. However those hopes have faded: the virus staged a recent resurgence in Iran amid actual blistering temperatures, and has had no trouble persisting in sultry Singapore.

But what happens to Covid-19, and us, when the rain and chill - and flu and sniffles - of autumn set in? Especially, how will the annual winter flu epidemic play out amid a Covid-19 pandemic?