"The emergence of the omicron variant has understandably captured global attention," said WHO Director-General Tedros Ghebreyesus at a press webinar on the COVID-19 pandemic.
"WHO takes this development extremely seriously, and so should every country. But it should not surprise us. This is what viruses do."
He said the omicron virus announced on Friday will continue to develop if the world allows it to continue spreading.
"We are learning more all the time about omicron, but there's still more to learn about its effect on transmission, the severity of disease, and the effectiveness of tests, therapeutics, and vaccines," Tedros noted.
He said the world must not forget that it is already dealing with a highly transmissible, dangerous variant – the delta – which currently accounts for almost all cases globally, including 90% of cases in Turkey.
"We need to use the tools we already have to prevent transmission and save lives from delta. And if we do that, we will also prevent transmission and save lives from omicron," added Tedros.
He warned that if countries and individuals don't take the necessary steps to stop transmission of the delta strain, "they won't stop omicron either."
Several WHO advisory groups had met to evaluate the emerging evidence and prioritize the studies needed to answer these questions over recent days.
The WHO chief again thanked Botswana and South Africa for detecting, sequencing, and reporting this variant rapidly.
"It is deeply concerning to me that those countries are now being penalized by others for doing the right thing," he said, repeating an earlier message.
Tedros called on all countries to take rational, proportional risk-reduction measures in keeping with the International Health Regulations.
"This includes measures to delay or reduce the spread of the new variant, such as screening of passengers prior to traveling and upon arrival or the application of quarantine to international travelers."
He explained that blanket travel bans would not prevent the international spread of omicron, and they place a heavy burden on lives and livelihoods.
Experts and vaccine producers are unsure if current vaccines will be enough to protect against the omicron variant. While Pfizer-BioNTech has reassured the public that its vaccine can withstand the highly mutated variant, Modern has been less optimistic.