In a technical brief issued on Dec. 17, the health agency said that Omicron has been detected in 89 countries so far, with “consistent evidence” that it has a substantial growth advantage over the Delta variant and warning that the rapid spread of the new mutation threatens to overwhelm many healthcare systems “quickly.”
Omicron has as many as 32 mutations in its spike protein, some of which the WHO described as “concerning” as they may be able to evade human immune response, potentially making it more transmissible.
“It is spreading significantly faster than the Delta variant in countries with documented community transmission, with a doubling time between 1.5–3 days,” the WHO said, adding that “it remains uncertain to what extent the observed rapid growth rate can be attributed to immune evasion, intrinsic increased transmissibility or a combination of both.”
While some preliminary indications suggest Omicron may be less virulent, and so less dangerous, the WHO said there is still limited data on its severity.
“A lot of the initial reports are that people with Omicron tend to have milder disease but it doesn’t mean that it’s not dangerous, it doesn’t mean that it’s quote unquote ‘only mild,'” Dr. Maria Van Kerkhove, an infectious disease epidemiologist and COVID-19 Technical Lead at the WHO, said on Dec. 16.
“With increased transmissibility, you’re going to have more cases,” she continued. “More cases mean more hospitalizations. More hospitalizations will mean more deaths.”
COVID-19 is the disease caused by the CCP (Chinese Communist Party) virus, also known as SARS-CoV-2.
Health experts in South Africa, where the variant was first discovered, have said Omicron was not driving up hospitalizations or fatalities in the country to a significant degree.
“According to scientific studies, this virus is spreading quicker than in previous waves, but the rates of hospitalizations and deaths remain relatively low,” South Africa’s Ministry of Health said in a news release Thursday.
But a new study by Imperial College in London found “no evidence” of Omicron causing less severe disease than Delta, though it noted that hospitalization data remains “very limited at this time.”
The study also found that the risk of reinfection with the Omicron variant is over five times higher than with Delta, which implies that the protection against Omicron afforded by prior infection could be as low as 19 percent.
Omicron is expected to become the most dominant strain in the United States within a few weeks, according to White House COVID-19 adviser Dr. Anthony Fauci, who warned that hospitals risk becoming overwhelmed.