Via The Guardian: What happens when flu meets Covid-19? Excerpt:
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?
One thing is a given. “We can expect waves of Covid in the fall,” says virologist Ab Osterhaus of the Research Centre for Emerging Infections and Zoonoses in Hanover. By then, he hopes, we might be better at treating severe cases, and more countries might be able to test, trace and quarantine all cases and their contacts, and contain the virus, better than they can now.
The biggest worry in the UK is that hospitals can struggle to cope with the winter flu season. This year they will have to cope with Covid-19 as well, which shows no sign of going away by then, and could even surge if it turns out that cold temperatures, or the circulation of other autumn and winter viruses, boost its spread.
The first problem will be figuring out which virus a patient has. Flu, Covid-19 and other seasonal respiratory diseases are virtually indistinguishable on the basis of symptoms, warns Barbara Rath of the University of Nottingham: even the loss of taste and smell many people get with Covid-19 is not unique. We need more and better diagnostic tests, she says, because the difference matters: medical staff need full protective gear to manage a Covid patient, but they can be vaccinated for flu.
The real unknown is what Covid-19 does around other viruses. Every autumn there is a predictable series of outbreaks of respiratory viruses. It starts with rhinovirus, the main cause of the common cold, which breaks out every September as young children go to school and swap mucus. As no parent needs to be told, children are to sniffles what mosquitoes are to malaria.
The rhinovirus subsides as most children are exposed and their immune systems activate. Then another virus breaks out: respiratory syncytial virus, or RSV. Every year in October or November, this causes mild colds in people of all ages, but sometimes severe lung infections in the youngest and oldest of us. RSV is so common that virtually all two-year-olds have already had it, and it sends more babies to hospital with pneumonia than any other virus.
Then RSV subsides, and the annual flu epidemic sets in, anywhere from early winter to spring, driven mainly by transmission among children, but taking its main toll among the elderly: some 8,000 on average die yearly of flu in the UK. This predictable parade of infections almost seems a spiteful campaign by viruses to keep people, especially families with young kids, sick for as long as possible.
But it is just a product of a little-understood phenomenon called “viral interference”: while one of these viruses holds sway in a person, or the population, for some reason the others can’t get a toehold. In September 2009, the swine flu pandemic that went on to sweep the world should have invaded Europe from the Americas. But the annual rhinovirus epidemic actually kept it at bay. The highly contagious new flu took over only when rhinovirus subsided, bumping RSV down the queue: RSV moved in only after that first wave of flu subsided.
The question now is where Covid-19 is going to fit amid this viral jostling. Not every virus takes turns like this, says Ian MacKay of the University of Queensland. Sometimes you can be infected by two at once. So which kind is Covid-19?
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