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The highly contagious B.1.1.7. variant of the coronavirus, which was first detected in the UK, has officially reached , but infectious disease experts say the true extent of its spread is unclear due to a lack of monitoring.

Texas, Minnesota and New York are among the states that have detected the variant. Given it has been found in 10 states, it is likely to be present in more, says Lane Warmbrod at Johns Hopkins University in Maryland. Still, she says, “it is hard to know how widespread the variant is because we don’t have sufficient genetic epidemiology capacity or capability in the US”.

William Hanage at Harvard University says the overall picture is unclear due to insufficient monitoring. Community spread is occurring in at least California, Florida and Colorado, he says, though in each community the variant is rare – for now.

The variant probably accounts for about 1 per cent of cases in the US today, estimates Eric Topol at Scripps Research Translational Institute in California. But the picture is foggy, he says. “Surveillance is extremely poor.”

New daily cases in the US currently stand at , but Gigi Gronvall, also at Johns Hopkins University, says the UK variant isn’t the reason for the surge in transmission. “The variant is almost certainly not driving our current explosion of cases, or we would have more immediately found it in many states,” she says.

Even if B.1.1.7. isn’t yet driving an acceleration in US cases, there is reason to think it will in the future, says Warmbrod, given research in the UK has found it to be between 40 and 70 per cent more transmissible than earlier variants. When the variant is established in the US, says Topol, it will trigger “a major surge that makes the US holiday surges look minimal”.

Surveillance to detect the spread of the variant in the US is poor, but not as bad as some recent media reports suggest, says Gronvall.

“It’s terrible by comparison with the UK. Recall that the UK has sequenced around 5 per cent of cases, which is huge. The comparative figure in the US is 10 times smaller,” says Hanage.

In Australia, where the spread of the coronavirus has been brought under control so far, detection of the UK variant has led to swift action to try to prevent any new outbreaks. On 7 January, a cleaner for a hotel quarantine facility in Brisbane tested positive for the variant. It had previously only been detected in returning international passengers in hotel quarantine, but this is the first time someone had been in the Australian community while potentially infectious.

The following morning, with no further positive cases, Queensland state premier Annastacia Palaszczuk announced a short, citywide circuit-breaker lockdown affecting some 2 million residents.

The city, where life has been normal for months, hadn’t locked down since the first wave in Australia in March.

“Doing three days now could avoid doing 30 days in the future,” said Palaszczuk on 8 January.

Within days, contact tracers identified around 150 of the cleaner’s casual and close contacts, who have all been quarantined. The city recorded only one new case of community transmission during the lockdown period – the cleaner’s partner – but it is too early to rule out further transmission. “We have to wait two weeks since the last possible exposure that index case had,” says Raina MacIntyre, an infectious diseases expert at the University of New South Wales in Sydney.

In response to the threat posed by new variants, the Australian government has brought forward its plan for mass vaccinations by a month. They are now set to start in February.

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