Professor Andrew Hayward, a member of the Scientific Advisory Group for Emergencies (Sage), told BBC Breakfast “only about half or maybe even fewer of people who do have Covid ever get tested”.
Speaking in a personal capacity, he said the doubling rate of Omicron would lead to an “extraordinary number of cases” and “a huge wave of infection”.
He added: “If you think about getting a year’s worth of rain over a month, then you’re going to get flooding and potentially severe flooding, no matter how much you’ve shored up your defences.
“And that’s the concern here – that that huge wave is going to cause lots of people to be off work having to isolate, which is going to cause disruption, and it’s going to spill over into people going into hospital.
“Now the rate at which it spills over is uncertain because we don’t know exactly how severe it is yet, but we’ve no particular reason to think that it’s less severe than previous strains.
“We know that Covid is always going to be less severe if you’ve been immunised but it may be that rather than the strain itself that’s making a lot of cases look less severe.”
He said more data should come around Christmas time or in the new year on severity, but added: “The trouble is, if you wait until then and don’t do anything to reduce the spread, then you’re in a much worse situation than if you take some action now.”
