U.S. officers maintain shut watch on the ‘delta plus’ mutation because it spreads within the U.Okay.

Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention, testifies before a Senate hearing on Health, Education, Labor and Pensions at the U.S. Capitol on May 11, 2021.

Jim Lo Scalzo | Swimming pool | Reuters

US health officials are watching an emerging Covid-19 sub-variant dubbed “Delta Plus,” which some scientists say is more contagious than the already highly transmissible Delta variant.

Formally known as AY.4.2, Delta plus contains two new mutations in the spike protein, A222V and Y145H, that allow the virus to enter the body. These mutations were found in other variants of Covid, so it is unclear how dramatic these changes will be on the virus.

Francois Balloux, director of the Genetics Institute at University College London, said it could be 10% -15% more contagious than Delta, which first appeared in India and, according to the Centers for Disease Control and Prevention, is spreading more easily than Ebola, SARS, MERS, and the 1918 Spanish flu.

According to CDC director Dr. Rochelle Walensky has an R-zero or reproduction rate of eight or nine, which means that every person who has Covid will pass it on to up to nine other people. The “wild type” or original strain of Covid had an estimated R-value of about three. Someone infected with the Delta variant carries 1,000 times the viral load of the original Covid strain.

India’s Ministry of Health reported in June that Delta plus was more transmissible than the Delta variant, adding that the subtype binds more tightly to lung cell receptors and could even reduce the effectiveness of monoclonal antibody treatments.

The mutation was discovered in the United States, but there has been no noticeable increase in Delta Plus cases nationwide, Walensky said at a Covid briefing at the White House on Wednesday.

“We are specifically monitoring sublines that could affect therapeutics such as monoclonal antibodies and vaccines,” said Walensky. “There is currently no evidence that subline AY.4.2 will affect the effectiveness of our current vaccines or therapeutics.”

The sub-variant AY.4.2 has been detected in at least five cases in the United States since August: in Washington, DC, California, North Carolina, Washington State and Massachusetts, see above Outbreak.info. The website collects data from GISAID, a global genome database on Covid and influenza cases.

Top health officials have been warning for weeks that stronger and potentially vaccine-resistant variants of Covid could develop as long as widespread outbreaks continue, fueled by billions of people around the world who remain unvaccinated. Dr. Anthony Fauci., White House Chief Medical Officer said in August that the US could be “in trouble” if another mutation crosses the delta, urging the unvaccinated to get their vaccinations in hopes of containing a surge that has crushed the nation’s health systems this summer.

Finally, Delta plus could also affect the age groups eligible to receive Covid booster doses, said Dr. Peter Marks, the Food and Drug Administration’s lead vaccine regulator, on Wednesday evening. The FDA and CDC have approved Covid boosters for a wide variety of US adults from all three manufacturers in the US: Modern, Johnson & Johnson and Pfizer.

“The exact age of this will be based on what we see of the emerging situation which is quite dynamic right now as we continue to see reports of new variants,” said Marks. “And we are also seeing changes in the epidemiology of Covid-19 in our country, with new hotspots emerging even as certain places become extinct.”

Concern about Delta Plus is high in the UK, where officials are grappling with a surge in cases and facing another health crisis. Delta Plus cases accounted for about 6% of all sequenced Covid cases in the week beginning September 27, according to the latest data from the country’s health authority. The subline is “becoming more common” in the UK, noted the agency and doctors from the National Health Service Confederation in London request a return to stricter Covid protocols in the winter.

But global health leaders urge the public not to panic. While the emergence of a Covid subtype does not equate to the development of an entirely new variant, tracking Delta’s progress could enable the medical community to better understand the mutation, says Dr. Sylvain Aldighieri, Covid-19 incident manager at the World Health Organization’s regional office for the Americas, said at a briefing on Oct. 6.

“When you look at these additional changes, it can help researchers track the variants on a fine scale,” Aldighieri said. “But they don’t imply any functional or biological difference.”

– Holly Ellyatt of CNBC in London contributed to this report.