Brazilian Covid variant: What happened in Brazil and why there are concerns over virus strain

Health workers wheel in a patient suspected of suffering from Covid-19 into a hospital in Brazil Credit: AP/Eraldo Peres

To understand why there’s concern about the “Brazilian variant” of Covid-19 you need to look to the Amazon city of Manaus.

Last year, it saw one of the world’s most severe waves of Covid. In May last year, 80 people a day were dying of the disease in a city of just two million people. By the time the wave passed, it was estimated that 76% of the population had antibodies to SARS-CoV-2, the virus that causes Covid.

Manaus was even held up as real-world evidence of “herd-immunity” to Covid. Cases fell sharply, presumably because levels of immunity in the population forced it to die out.

But in December, cases started to rise again. Manaus saw a wave of infections more severe than its first. Hospitals ran out of oxygen, undertakers ran out of coffins. The most likely explanation for the phenomenon was a new variant of SARS-CoV-2 referred to as P.1.

The virus has key mutations that might enable it to evade antibodies to previous strains. This led to people previously infected getting infected again. There are anecdotal reports of widespread reinfection during the second wave in Manaus.

If reinfection is occurring, that raises the prospect that vaccines (which are based on “classic” strains of SARS-CoV-2) will also be less effective. While this hasn’t been confirmed in Brazil the strain shares key mutations with the one which was first identified in South Africa and there is documented evidence on the vaccines being less effective against that strain.

Now it’s here in the UK that inevitably raises concerns. However, right now, the variant probably has no real “edge” over its viral cousins already in circulation.

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It carries the same mutation that allows the UK or “Kent” variant to be up to 70% more transmissible that previous strains. But there’s no evidence the Brazil variant is as transmissible as our own. It may never out-compete our own, home-grown variant of Covid. What’s more, we’re still in lockdown. So right now, the Brazil variant has very little to give it the opportunity to spread.

That of course, could all change. We’re about to start easing lockdown restrictions and we’re also vaccinating more and more of the population. If the Brazil variant can still infect some people who’ve been vaccinated it may find an opportunity to spread.

The only way to deny it that opportunity is to trace and isolate any cases of P.1 that occur, and maintain surveillance for these new variants as lockdown is eased, and vaccines are rolled out more widely.