New Yr, Identical Variant
CDC’s purpose is to offer actionable info to public well being professionals and the American public. As a result of Omicron sublineage XBB.1.5 knowledge had been displayed individually from XBB knowledge on COVID Information Tracker’s Nowcast projections for the primary time final week, we thought it might be useful to clarify the completely different variant proportion info CDC gives. This contains how the Nowcast forecasting device works—what it’s (a projection primarily based on a mannequin that has been correct over time) versus what it isn’t (a literal, real-time depend of variants primarily based on sequenced viruses from folks with COVID-19).
CDC makes use of two strategies to show variant proportions: weighted estimates and Nowcast estimates. Weighted estimates for every circulating lineage are very exact, however it takes two to 3 weeks for pattern assortment, specimen therapy, delivery, and evaluation to happen. CDC makes use of Nowcast to forecast variant proportions earlier than the weighted estimates can be found.
Sublineages with weighted estimates lower than 1% of all circulating variants are mixed with their dad or mum lineage for reporting of each weighted and Nowcast estimates. Variant proportion estimates for XBB.1.5 had been first separated from its dad or mum (XBB) the week of December 31, when its most up-to-date weighted estimate (primarily based on info from the week of December 10) rose to about 4%. Due to its quick development charge, its Nowcast estimate was projected to be round 41% by the top of December.
However projections might be unsure when a variant is simply starting to unfold. When Nowcast predicted XBB.1.5 at 41%, there was a large prediction vary of about 23% to 61%. Since then, extra knowledge have are available in from mid-December, in addition to further knowledge delayed by the vacations. In consequence, the projection for the week ending December 31 was revised to 18%, however with a better diploma of certainty (prediction vary of 9% to 33%), adopted by a rise to twenty-eight% for the newest week of January 6 (prediction vary of 14% to 47%).
These findings exhibit that XBB.1.5 is spreading shortly. Right now, CDC’s COVID-19 steerage stays the identical about how folks can greatest shield themselves from critical sickness. CDC will proceed to research the methods wherein XBB.1.5 could also be completely different from different Omicron lineages and can proceed to replace COVID Information Tracker’s Variant Proportions web page on a weekly foundation.
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