New Delhi: Top US scientist Anthony Fauci has said that the Omicron Covid-19 variant was "almost certainly" not more severe than the Delta variant.


"The new variant is clearly highly transmissible, very likely more so than Delta. However, it almost certainly is not more severe than Delta," Anthony Fauci, President Joe Biden's chief medical advisor, told AFP.'


He said data from around the world indicated re-infections were higher with Omicron Covid-19 variant. The Omicron coronavirus variant has been confirmed in more than 25 countries after it was initially detected in South Africa in November.


"There is some suggestion that it might even be less severe, because when you look at some of the cohorts that are being followed in South Africa, the ratio between the number of infections and the number of hospitalisations seems to be less than with Delta," AFP quoted Fauci as saying.


Fauci said the "best case scenario" was a more transmissible virus that doesn't cause more severe illness and doesn't lead to a surge of hospitalizations.


"The worst case scenario is that it is not only highly transmissible, but it also causes severe disease and then you have another wave of infections that are not necessarily blunted by the vaccine or by people's prior infections," he said.


Scientists said the Omicron variant has about 50 mutations, including more than 30 mutations on the spike protein that the coronavirus uses to attach to human cells.


After being classified as a "Variant Of Concern" by the WHO, several countries have limited travel from southern Africa and imposed other restrictions for fear it could spread quickly even in vaccinated people.