A third strain of COVID-19 featuring a mutation which makes it more infectious has been discovered. Worryingly, it also contains a mutation that gives it an enhanced ability to avoid antibodies.
And it appears to have evolved completely separately to strains in the UK and South Africa with the same mutations.
The new strain, dubbed B.1.1.248, was detected in four travellers from Brazil who touched down in Japan on January 2, local health officials said. They tested positive on January 6.
"Over the weekend WHO was notified by Japan about a new variant of the virus," World Health Organization (WHO) Director-General Tedros Adhanom Ghebreyesus said on Monday (local time).
"The more the virus spreads, the higher the chance of new changes to the virus - most notably transmissibility of some variants of the virus appears to be increasing."
Like the UK and South African strains, it has the N501Y mutation which increases its infectiousness about between 40 and 80 percent. Thankfully this mutation doesn't appear to affect the efficacy of the existing COVID-19 vaccines, but the more it spreads the higher chance it has of developing one that does.
"The N501Y mutation (shared by all three) seems to bind the human ACE2 receptor more strongly, and more infectious, but doesn't seem to affect the vaccine," tweeted epidemiologist Eric Feigl-Ding of the Federation Of American Scientists, one of the first to warn SARS-CoV-2 was likely to cause a pandemic.
"But beware many headlines don't make it clear it's only this mutation that doesn't [affect the] vaccine."
Like the South African strain, B.1.1.248 it also has the E484K mutation - disguising itself to the immune system's antibodies, raising fears it will have a greater ability to reinfect recovered patients. But they don't appear to be directly related.
Alex Rubinsteyn, an assistant professor at the University of North Carolina School of Medicine, said the mutations happened independently of the UK and South African strains.
"Watching the parallel emergence of the same variant combinations at the same time is kinda wild," he tweeted. "Letting a novel virus infect 1B+ hosts is really one for the textbooks."
An earlier study found the virus appears particularly keen to evolve the E484K mutation. Scientists in Italy who tried to speed up the evolution of the virus in a lab to see what would happen also managed to produce the E484K mutation.
While it's believed the N501Y mutation won't affect the efficacy of existing vaccines, it's not clear if the same will hold for the E484k mutation.
Takaji Wakita, head of the Japanese National Institute of Infectious Diseases, told reporters all they had to date was the genetic code and it was too early to tell what effects the 12 mutations it has - including E484K and N501Y - will have on transmissibility and severity.
"What's most critical is that we sequence the virus effectively so we know how it's changing and how to respond," Dr Tedros said. "For example, while diagnostics and vaccines still seem to be effective against the current virus, we may need to tweak them in the future."
Moderna, the company behind one of the first approved COVID-19 vaccines, says thanks to its state-of-the-art mRNA technology it should only take a matter of weeks to tweak existing vaccines to fight any mutations which help the virus escape antibodies - the only hold-up beyond that would be regulators.
The UK and South African strains have quickly become dominant in their respective countries, and their presence at our border in New Zealand has led to calls for increased vigilance, and perhaps even a ban on travellers from those nations and others suffering uncontrolled outbreaks, such as the US.
The WHO says it is looking closely into the Japan/Brazil variant, and is urging countries to up their sequencing in case there are other mutations out there still waiting to be found.