U.S. officials are closely monitoring COVID-19 cases and hospitalizations in the United Kingdom — which have continued to rise over the last few weeks — and are considering what it could mean for the U.S.
Seven things to know:
1. U.K. COVID-19 cases have jumped 36.8 percent in seven days, according to government data last updated March 21. Meanwhile, hospitalizations are also rising, though not as quickly, with a 25.1 percent increase in COVID-19 patient admissions in the last seven days. Both metrics have been simultaneously rising for multiple weeks, an unusual trend given increases in COVID-19 cases preceded hospitalization increases by about 10 days to two weeks in previous waves.
2. U.K. authorities have attributed the rising cases and hospitalizations to the BA.2 variant, which is more transmissible than the original omicron strain; the opening of society, with people socializing indoors without masks; and waning immunity from vaccination or prior infection.
3. BA.2 makes up a small portion of COVID-19 cases in the U.S. but has been growing steadily, according to outbreak.info. The seven-day rolling average of percent of BA.2-positive sequences in the U.S. was 27 as of March 15, up from 17 percent March 7. By comparison, the seven-day average of percent of BA.2-positive sequences in the U.K. was 86 percent as of March 15, the latest date for which data is available.
4. "Omicron BA.2 is about 1.4 times more infectious than BA.1. The basic reproduction number (R0) for BA.1 is about 8.2, making R0 for BA.2 about 12," Adrian Esterman, PhD, former epidemiologist for the World Health Organization, tweeted March 9. "This makes it pretty close to measles, the most contagious disease we know about."
5. Over the next few weeks, the U.S. will likely see an increase in BA.2 cases, but it may not lead to as severe a surge in hospitalizations or deaths, Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, told ABC News on March 18.
6. Although U.S. cases are at the lowest levels since July, some early evidence via wastewater surveillance shows cases increasing in 35 percent of communities, according to NPR. There are about 700 wastewater sampling sites nationwide. Increases might just be temporary bumps, though the CDC said it has seen consistent increases in Florida, Rhode Island and West Virginia as of March 18, according to NPR.
7. "So the bottom line is we likely will see an uptick in cases, as we've seen in the European countries, particularly the U.K., where they've had the same situation as we've had now," Dr. Fauci said in a transcript cited by NPR.