Health officers in the United States are keeping a close eye on a new Covid-19 subvariant known as "delta plus," which some scientists believe may be more contagious than the already highly transmissible delta variant.
Delta plus, also known as AY.4.2, contains two new spike protein mutations, A222V and Y145H, allowing the virus to enter the body. Because those mutations have been found in other Covid variants, it's unclear how much of an impact they have on the virus.
According to the Centers for Disease Control and Prevention, it could be 10 percent -15 percent more contagious than delta, which first appeared in India and spread faster than Ebola, SARS, MERS, and the 1918 Spanish flu. According to CDC Director Dr. Rochelle Walensky, Delta has an R-naught, or reproduction rate, of eight or nine, which means that every person who has Covid will transfer it to up to nine more people. The R-naught of Covid's "wild type" or initial strain was determined to be around three. The delta variation infects people with 1,000 times the viral load of the original Covid strain.
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Delta plus is more transmissible than the delta variation, according to India's Ministry of Health, and the subtype binds more firmly to lung cell receptors, potentially reducing the efficacy of monoclonal antibody therapy.
The mutation has been detected in the U.S., but there hasn’t been a noticeable uptick in delta plus cases nationwide, Walensky said at a White House Covid briefing Wednesday.
“We particularly monitor for sublineages that could impact therapeutics, such as monoclonal antibodies and vaccines,” Walensky said. “At this time, there is no evidence that the sublineage AY.4.2 impacts the effectiveness of our current vaccines or therapeutics.”
According to Outbreak.info, the AY.4.2 subvariant has been found in at least five cases in the United States since August: in Washington, D.C., California, North Carolina, Washington state, and Massachusetts. GISAID, a global genetic database on Covid and influenza cases, is used to populate the webpage.
For weeks, top health officials have warned that increasingly aggressive and potentially vaccine-resistant Covid strains could emerge as long as massive outbreaks continue, spurred by billions of unvaccinated individuals around the world. Dr. Anthony Fauci, the White House senior medical advisor, warned in August that the United States might be "in peril" if another variant surpassed delta, urging the unvaccinated to get their immunizations in the hopes of preventing a surge that crippled the country's healthcare systems this summer.
Dr. Peter Marks, the Food and Drug Administration's senior vaccine regulator, said Wednesday night that Delta plus could eventually alter the age categories eligible for Covid booster doses. In the United States, the FDA and the CDC have approved Covid boosters for a wide range of individuals from all three manufacturers: Moderna, Johnson & Johnson, and Pfizer.
“The exact age of that will be based on what we see of the emerging situation, which is quite dynamic right now because we continue to see reports of new variants coming up,” Marks said. “And we’re also seeing changes in the epidemiology of Covid-19 in our country right now with new hotspots coming up even as certain places die down.”
Concerns about delta plus are running high in the United Kingdom, where officials deal with an uptick in cases and a resurgent health issue. According to the latest data from the country's Health Security Agency, Delta plus cases accounted for around 6% of all sequenced Covid cases as of the week commencing Sept. 27. The agency added that the sublineage is "growing in frequency" in the United Kingdom. Doctors from London's National Health Service Confederation advocate returning to tougher Covid procedures as the winter approaches.
But global health leaders are urging the public not to panic. Though the emergence of a Covid subtype isn’t the same as an entirely new variant evolving, keeping track of delta’s progression could allow the medical community to understand better the mutation, Dr. Sylvain Aldighieri, Covid-19 incident manager at the World Health Organization’s regional branch for the Americas, said at a briefing Oct. 6.
