BF.7: 5 notes on the subvariant fueling surge in China

Global health experts are closely monitoring COVID-19 activity in Beijing where the highly transmissible omicron subvariant BF.7 is fueling a surge in cases.

"WHO is very concerned over the evolving situation in China with increasing reports of severe disease," Tedros Adhanom Ghebreyesus, PhD, director-general of the World Health Organization, said during a Dec. 21 news briefing. "In order to make a comprehensive risk assessment of the situation on the ground, WHO needs more detailed information on disease severity, hospital admissions, and requirements for ICU support."

Five updates: 

1. BF.7 has one additional genetic mutation in the spike protein compared to BA.5, its parental strain. Initial reports from China suggest the subvariant is the most transmissible of all circulating in the country, with a shorter incubation period and greater ability for immune escape, according to CBS News.

2. Scientists estimate BF.7's basic reproduction number — or the number of cases directly caused by an infected individual throughout his or her infectious period — is 10 to 18.6. In comparison, the original omicron strain's reproduction number is about 5, according to the report.  

3. Despite BF.7's ability to spread quickly and evade immunity, the subvariant's prevalence has not spiked in other countries. In fact, BF.7's prevalence has declined slightly in the U.S. in recent weeks amid BQ.1 and BQ.1.1's dominance. BF.7 accounted for 4.9 percent of all COVID-19 cases in the week ending Dec. 17, down from 5.8 percent the week prior, according to the CDC's latest variant proportion estimates

4. It's still unclear why BF.7 is fueling a surge in China and not other countries. Experts said China may have a low level of immunity, which could explain the subvariant's high reproduction number in the country, according to CBS News.  

5. Although the number of weekly reported COVID-19 deaths has fallen by nearly 90 percent globally since peaking last January, there are still too many uncertainties to say the pandemic is over, Dr. Tedros said during the WHO briefing.


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