Geneva, The World Health Organization (WHO) welcomed the positive results of dexamethasone in treating the novel coronavirus, while warning that the drug should not be used on mild cases or for prevention purposes.

At a virtual press briefing on Wednesday, WHO Director-General Tedros Adhanom Ghebreyesus congratulated the initial results from the RECOVERY trial in the UK, which shows that dexamethasone, a common steroid, has had a beneficial effect on patients severely ill with COVID-19, reports Xinhua news agency.

For patients on ventilators, the treatment was shown to reduce mortality by about one third, and for patients requiring only oxygen, mortality was cut by about one fifth, according to preliminary findings received by WHO.

"This is very welcome news for those patients with severe illness," said Tedros, adding: "However, dexamethasone was shown to not have a beneficial effect for those with milder disease, who did not need respiratory support."

Echoing the warning of the WHO director-general, Michael Ryan, executive director of WHO Health Emergencies Program, highlighted that dexamethasone, as a "very powerful anti-inflammatory drug", must be used under medical supervision.

"In fact, steroids -- particularly powerful steroids -- can be associated with viral replication. In other words, they can actually facilitate the division and replication of viruses in human bodies," said Ryan.

"It is not a treatment for the virus itself. It is not a prevention for the virus," he said, adding: "It's exceptionally important in this case that this drug is reserved for use in severely ill."

According to Ryan, the findings from the UK, though significant, were "still just preliminary data from one study", and the WHO needs to see the final data before updating the clinical guidance and supporting countries to access and utilizing the drug in the most appropriate way possible.