A South African health researcher said early data suggests the Omicron variant of coronavirus is highly transmissible.

But Professor Willem Hanekom, director of the Africa Health Research Institute in South Africa, said it has a less than 1% chance of re-infection and typically results in “milder” disease.

Speaking on The Andrew Marr Show, Professor Willem Hanekom, said: “We know three things that we didn’t know last week, the first thing is that the virus is spreading extraordinarily fast in South Africa, the increase in cases is much steeper than it’s been in the past three waves so it seems that Omicron is able to spread very easily and virtually all the cases that we see in South Africa right now are Omicron.

“The second thing we have data on is re-infections, so as you know, after you’ve had Covid you have about a 1% chance, or perhaps even less than a 1% chance, of getting re-infected and even getting disease again, of course, by this virus.

“The third little bit of data we have already relates to clinical cases and how severe the disease is.

“The only data suggests the disease may occur more in younger people and mostly younger people who are unvaccinated and overall so far the disease has appeared to be milder but again I want to say we have to be cautious – these are very early days.”

It came as the latest figures from the UK Health Security Agency (HSA) showed as of Saturday, a further 26 cases of the Omicron variant had been reported across the UK – taking the total so far to 160.

On Saturday it was announced all passengers arriving in the UK will have to take a Covid pre-departure test amid fears about the spread of the Omicron variant.

Ministers said it was intended to be a temporary measure following new data showing an increase in the number of cases of the new strain linked to foreign travel.

The new measures for England, which come into force at 4am on Tuesday, were announced late on Saturday by Health Secretary Sajid Javid and were immediately followed by the Scottish and Welsh government.

It means passengers travelling to the UK will have to take either a PCR or a lateral flow test up to a maximum of 48 hours before they depart regardless of their vaccination status.

The Department of Health and Social Care (DHSC) said it had acted in part because said new analysis by the UK Health and Security Agency (HSA) suggested the window between infection and infectiousness may be shorter for the Omicron variant.

It said this increased the efficacy of pre-departure testing, making it more likely it would to identify positive cases before travel.

In a further move the Government said that Nigeria was being added to the travel red list after 21 cases of the Omicron variant in England were linked to travel from the west African nation.

From 4am on Monday only British and Irish nationals and residents travelling from Nigeria will be allowed into the country and must isolate in a Government-managed quarantine hotel.

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