“The overall global risk related to the new [variant of concern] Omicron is assessed as very high.”

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Despite the warnings, a number of key questions about the variant, which was first detected in southern Africa earlier this month, remained unanswered. These include whether it can spread more easily between people, whether it can dodge vaccine protections, and whether it causes more severe disease than previous strains.

“A number of researchers in South Africa and other countries are carrying out studies to assess these characteristics of Omicron. Depending on these characteristics, if another major surge of Covid-19 takes place driven by Omicron, consequences may be severe,” the WHO said.

“Increasing cases, regardless of a change in severity, may pose overwhelming demands on healthcare systems and may lead to increased morbidity and mortality.”

Early evidence from surveillance in South Africa, which reported the variant to the WHO on November 24, suggests the variant has a growth advantage over the highly transmissible Delta strain, which is dominant now.

Infections had increased steeply in recent weeks in the country, coinciding with the detection of the variant, the WHO said on Sunday.

Preliminary evidence also suggested there might be an increased risk of reinfection with Omicron, meaning the immune systems of people infected with other strains might not be able to recognise the mutated strain.

The variant raised concern among scientists due to the number of changes concentrated in the spike protein – part of the virus targeted by many vaccines. The WHO said these included between 26-32 changes of amino acids in the spike protein, as compared with the reference strain.

Some of these changes have also been seen in other variants like Delta and Alpha, where they are thought to help the virus infect people or dodge the immune system’s antibodies, scientists have said.

“Overall, there are considerable uncertainties in the magnitude of immune escape potential of Omicron,” the WHO said in its technical brief, which called on countries to prepare their health systems for potential surges.

“Further research is needed to better understand the escape potential against vaccine- and infection induced immunity. Research efforts are ongoing, and the data are expected to be available in the coming weeks.”

The WHO also called on countries to bolster their surveillance systems and ensure their health systems were prepared.

It asked governments to share as much information as possible on the behaviour and characteristics of the virus, severity of the disease in infected people, and effectiveness of disease control measures.

Standard measures like the use of masks, physical distancing, and hand hygiene remained important, but might need to be improved with a more transmissible variant to prevent spread, the WHO said.

More than a dozen countries had identified cases of the variant within their borders as of Monday afternoon.



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