CDC adds omicron subvariant BA.2 to online tracker
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The CDC has begun reporting the proportion of COVID-19 cases in the United States that are caused by the omicron subvariant BA.2.
In the week ending Feb. 5, the original omicron variant of SARS-CoV-2 was responsible for 96.4% of all COVID-19 cases, according to the CDC’s online variant tracker. BA.2 caused the remaining 3.6% of cases — up from 1.2% the week before.
“BA.2 is more transmissible than BA.1” — the original omicron variant — “so we expect to see BA.2 increasing in detection around the world,” Maria Van Kerkhove, PhD, an infectious disease epidemiologist and WHO’s COVID-19 technical lead, told reporters this week.
According to Catherine L. Troisi, PhD, an epidemiologist at the University of Texas Health Science Center at Houston, a subvariant is formed the same way a normal variant is formed.
“A subvariant ... shows some of the properties of the variant and then some changes,” Troisi told Healio. “For example, BA.2 seems to have 20 more spike mutations than the BA.1.”
A CDC spokesperson told Healio that the agency “continues to monitor variants that are circulating both domestically and internationally.”
In Denmark, BA.2 has grown to become the dominant variant after accounting for about 20% of the country’s cases in the final week of 2021. By the week ending Jan. 15, that proportion had grown to 45%.
“Denmark is the place where it was first identified,” Troisi said. “Now, about two-thirds of cases in Denmark are BA.2.”
According to Troisi, BA.2 has been reported in about 60 countries and in 25 American states.
“Luckily, BA.2 does not seem to cause more severe disease, but we're early. It hasn't been around that long,” she said. “It appears that vaccine will protect you against BA.2 just as well as it does against BA.1. So, not perfectly, but at least there's some protection there.”
References:
CDC. COVID Data Tracker. https://covid.cdc.gov/covid-data-tracker/#variant-proportions. Accessed Feb. 10, 2022.
Statens Serum Institute. Now, an omicron variant, BA.2, accounts for almost half of all Danish omicron-cases. https://en.ssi.dk/news/news/2022/omicron-variant-ba2-accounts-for-almost-half-of-all-danish-omicron-cases. Accessed Feb. 2, 2022.
WHO. Live Q&A on COVID-19 and omicron subvariant BA.s with Dr. Maria Van Kerkhove and Dr. Abdi Mahamud. Published Feb 8, 2022. Accessed Feb. 11, 2022.
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CDC. COVID data tracker: Variant proportions. https://covid.cdc.gov/covid-data-tracker/#variant-proportions. Accessed Feb. 10, 2022.
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