Why should we treat COVID-19 like norovirus – not the flu

Of course, SARS-CoV-2 – the virus that causes COVID-19 – does share some characteristics with influenza viruses, which makes comparisons tempting. Around 20% of people have no symptoms at all when infected with SARS-CoV-2, and many people infected with a flu virus also don’t get sick. Both viruses are prone to a lot of mutation. And with both diseases, older people and people with weakened immune systems are at a higher risk of severe illness than healthy young adults, with infections spreading rapidly in care homes, hospital wards and schools.

But a lot of these traits are also shared by another germ: the norovirus. It too can be asymptomatic in some people, and mutates rapidly – different strains of norovirus have been found circulating around the same hospital during one season. In fact, as it spreads around, norovirus sometimes changes so much that standard testing kits can’t recognise versions of it that have evolved.

Most people with symptomatic norovirus infections have diarrhoea, but some experience projectile vomiting as well. This creates an aerosol full of virus that spreads around any room and leaves it on surfaces, waiting for others to pick it up, as happens with respiratory viruses. COVID-19 also causes diarrhoea in some patients. Flu is not the only viral disease that COVID-19 can be compared to.


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