US health officials have sharply cut their estimates for how much of the country’s Covid-19 wave has been caused by the Omicron coronavirus variant, underlining the uncertainties surrounding the country’s pandemic response.
The US Centers for Disease Control and Prevention on Tuesday said they now believe the highly transmissible strain is responsible for just over half of the country’s Covid infections, rather than three-quarters, as estimated a week ago.
The change to CDC’s estimates came after the agency received more sampling information from previous weeks, officials said. But they also highlight the difficulties federal health officials have faced in trying to gain an accurate picture of the pandemic in the US, given that so much health data is held at local and state levels.
A spokesperson said: “There was a wide predictive interval posted in last week’s chart, in part because of the speed at which Omicron was increasing. We had more data come in from that timeframe and there was a reduced proportion of Omicron.
“It’s important to note that we’re still seeing a steady increase in the proportion of Omicron.”
CDC shocked many in the US health community last week when it said Omicron now accounted for 73 per cent of cases, up from 13 per cent in the previous week. However, the new figures show a more gradual increase over the past three weeks, from 7 per cent, to 23 per cent, and now 59 per cent.
Overall case numbers in the US continue to climb, with some parts of the country now having record numbers of infections. Hospitalisations and deaths have risen far more slowly, though, mirroring the experience of places such as South Africa and the UK.
The latest wave of cases has caused widespread disruption, with many people having to isolate for lengthy periods of time despite suffering mild symptoms or none at all. Nearly 1,000 US flights were cancelled on Tuesday morning, according to flightaware.com, adding to thousands that were cancelled over the Christmas weekend.
CDC attempted to correct that on Monday, slashing the recommended quarantine period for infected people from 10 days to five, as long as symptoms have passed or are resolving.
But that move brought criticism from some of the public health scientists on whose support the Biden administration has largely been able to rely.
Eric Topol, director of the Scripps Research Translational Institute in California, said: “It seems pretty chaotic. You have an announcement yesterday on isolation guidance with no data, no evidence, nothing. And this is from an administration that says it wants to stick to the science.
“Then today we have the drastic changes to their genomic estimates. The last 24 hours show that the credibility of the agency is lower than it has been at any point during this administration.”
The Biden administration has also faced criticism in recent weeks over the shortage of Covid testing capacity in the US, with lengthy queues building at test sites as Omicron has surged.
Last week, the US president announced that the federal government would respond by distributing 500m at-home tests. Speaking to reporters on Wednesday, Biden said his administration had “a bit of progress” on distributing the test kits.
He added that he would make a decision on whether to mandate vaccines for all travellers on domestic flights in the US “when I get a recommendation from the medical team”.