With coronavirus cases rising in parts of Europe and Asia, scientists worry that an extra-contagious version of the omicron variant may soon push cases up in the United States too.
Experts are also keeping their eyes on another mutant: a rare delta-omicron hybrid that they say doesn鈥檛 pose much of a threat right now but shows how wily the coronavirus can be.
The U.S. will likely see an uptick in cases caused by the omicron descendant BA.2 starting in the next few weeks, according to Dr. Eric Topol, head of Scripps Research Translational Institute.
鈥淚t鈥檚 inevitable we will see a BA.2 wave here,鈥� he said.
One reason? After about two months of falling COVID-19 cases, pandemic restrictions have been lifted across the U.S. Many people are taking off their masks and returning to indoor spaces like restaurants and theaters.
And the latest data from the Centers for Disease Control and Prevention shows The CDC reported Tuesday that the variant accounted for about 35% of new infections last week. In the Northeast, it was about half.
Dr. Anthony Fauci, the U.S. government鈥檚 top infectious disease expert, told ABC鈥檚 鈥淭his Week鈥� over the weekend that he also thinks the U.S. will likely face an 鈥渦ptick鈥� similar to what鈥檚 happening in Europe, particularly the United Kingdom, where BA.2 is the dominant strain. He said he doesn鈥檛 think it will be a 鈥渟urge.鈥�
The U.K. has 鈥渉ad the same situation as we鈥檝e had now,鈥� Fauci said. 鈥淭hey have BA.2. They have a relaxation of some restrictions such as indoor masking and there鈥檚 a waning of immunity鈥� from vaccines and past infections.
Keri Althoff, a researcher at Johns Hopkins Bloomberg School of Public Health, cautioned that CDC case counts underestimate the true numbers because some people are no longer getting tested and others are testing at home and not reporting the results. Also, she said, not every specimen is genetically sequenced to determine the variant.
It鈥檚 clear, she said, 鈥淏A.2 is coming onto the scene.鈥�
One reason the variant has gained ground, scientists say, . In rare cases, research shows it can sicken people even if they鈥檝e already had an omicron infection 鈥� although it doesn鈥檛 seem to cause more severe disease.
Vaccines appear just as effective against both types of omicron, but breakthrough infections are possible. And experts point out that vaccination rates are lower in the U.S. than the U.K. About 74% of those 12 and older are fully vaccinated in the U.S, compared with 86% in the U.K.
鈥漌e need to emphasize that we鈥檙e not protected in this country compared to peer countries,鈥� Topol said.
Still, not all experts are equally concerned about a BA.2-related rise in U.S. cases. Dr. James Musser, head of genomic medicine and infectious diseases at Houston Methodist, said the variant has so far only caused about 1% to 3% of cases in his medical system. Cases there have usually tracked closely with what鈥檚 happening in the U.K.
He called BA.2 鈥渟omething we鈥檙e keeping an eye on,鈥� but said, 鈥淚鈥檓 not losing sleep鈥� over it.
That鈥檚 how many scientists view the other variant that some in the public are calling 鈥渄eltacron,鈥� a hybrid containing genetic information from both delta and omicron.
Earlier this month, Maria Van Kerkhove of the World Health Organization said the hybrid has been detected at 鈥渧ery low levels鈥� in France, the Netherlands and Denmark. And two recent studies, which have not yet been peer-reviewed, point to a tiny number of cases in the U.S.
Much remains unknown about the hybrid. There鈥檚 no evidence it causes more severe disease, and it doesn鈥檛 look like it鈥檚 infecting many people. CDC researchers identified 9 samples, seven from the mid-Atlantic region in a that hasn鈥檛 yet been peer-reviewed. Topol, who was not involved in the research, said there鈥檚 no evidence it has the potential to spread.
It鈥檚 common for coronaviruses to shuffle gene segments, said Dr. Stuart Campbell Ray, an infectious disease expert at Johns Hopkins University. With two variants circulating at the same time, people may get double infections, and a 鈥減rogeny virus鈥� could emerge.
Given the virus鈥� 鈥� and the rise of BA.2 鈥� experts say people should get vaccinated if they鈥檙e not and keep their masks handy.
鈥淜eep your guard up,鈥� Topol said. 鈥淭his is not over.鈥�
