Omicron is fastest spreading COVID-19 strain: The latest CDC, WHO updates

The omicron variant is spreading faster than any other COVID-19 variant, the World Health Organization warned during a Dec. 14 news conference

"Omicron is spreading at a rate we have not seen with any previous variant," said Tedros Adhanom Ghebreyesus, PhD, WHO director-general. Preliminary findings from researchers in South Africa, where omicron was first detected, suggest the variant spreads more than twice as fast as delta, currently the dominant strain in the U.S. 

Omicron has been detected in at least 77 countries, he added. As of Dec. 15, the variant has been identified in at least 35 states.

"The reality is that omicron is probably in most countries, even if it hasn't been detected yet," Dr. Tedros said. 

Five more updates:

1. For the week ending Dec. 11, the omicron variant accounted for 3 percent of new infections in the U.S. — up from 0.4 percent the previous week, according to genomic surveillance data from the CDC. In New Jersey and New York, the strain accounts for 13 percent of new cases, CDC director Rochelle Walensky, MD, said Dec. 14. 

2. In a separate Dec. 14 briefing cited by the The Washington Post, CDC officials cited data about omicron's increased transmissibility and said they estimate the strain may cause a surge in infections and reach a peak in January. 

CDC officials also discussed two potential situations regarding potential surges. The first involves a large wave of omicron and delta infections arriving as soon as next month, around the same time flu and winter cold cases tend to rise. Health officials deemed this situation the worst-case scenario, a "triple whammy" that could  overwhelm health systems. The second scenario involves smaller omicron surges in the spring. Officials were uncertain which scenario is more likely. 

3. Dr. Tedros voiced concern that officials worldwide might be dismissing the variant as less transmissible and warned against underestimating the virus. 

"Even if omicron does cause less severe disease, the sheer number of cases could once again overwhelm unprepared health systems," he said. 

Preliminary real-world data from South Africa indicate the variant causes less severe illness, with the risk of hospitalization among people who contracted COVID-19 during a surge in omicron cases 29 percent lower relative to the initial wave in 2020. Among 43 cases linked to omicron in the U.S. between Dec. 1 and 8, infections were mostly mild, with one hospitalization and no deaths, the CDC reported Dec. 10. 

4. Global health officials emphasized mitigation measures won't completely halt omicron's spread, but they could avert worst-case scenarios. Mike Ryan, MD, head of WHO's health emergencies program, urged the public to continue mask wearing and proper hand washing while encouraging governments to enact layered measures that support communities and health systems.

"If we all apply those measures, we won't stop transmission of omicron or delta — it is very hard to stop," Dr. Ryan said during the Dec. 14 COVID-19 update. "But what we will do is critically reduce the force of infection, we will reduce that pressure wave, and then hopefully get through this wave in a way in which we don’t disrupt or collapse our public health systems." 

"It's not vaccines instead of masks. It's not vaccines instead of distancing. It's not vaccines instead of ventilation or hand hygiene. Do it all. Do it consistently. Do it well," Dr. Tedros said. 

5. Omicron is more likely to evade the protection of Pfizer-BioNTech's vaccine against infection, preliminary real-world findings from South Africa suggest. Still, the vaccine offered 70 percent protection against hospitalization in fully vaccinated people. 


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