Two new Omicron sub-variants, whose virulence is yet to be determined, are causing a new wave of the COVID-19 pandemic in South Africa, according to AFP quoting WHO chief.

Tedros Adhanom Ghebreyesus, WHO Director-General said, "Globally reported cases and deaths from COVID-19 are continuing to decline with reported weekly deaths at their lowest since March 2020. But these trends, while welcome, don't tell the full story."

"The South African scientists who identified Omicron late last year have now reported two more Omicron sub-variants BA.4 and BA.5 are the reason for a spike in cases in South Africa," he added.

"It's too soon to know whether these two sub-variants can cause more severe diseases than other Omicron sub-variants, but early data suggest vaccination remain protective against severe diseases and deaths," he said.