Deltacron: What We Know About This Hybrid Variant

By:

Rachel Nania,

While Americans brace for a potential bump in COVID-19 cases caused by the spreading BA.2 subvariant of omicron, experts are monitoring another version of the virus — one that’s a hybrid of

both the delta and omicron variants. 

What’s being called deltacron informally, and AY.4/BA.1 by scientists, has been detected in a handful of countries, including France, Denmark, Belgium, Germany and the Netherlands. A few

cases have also been reported in the U.S., a preprint study shows.  

But despite its infamous parents and splashy name, deltacron — which is really a catchall term for a strain that carries genetic characteristics from both delta and omicron — doesn’t appear

to be a big threat at the moment, experts say. It’s currently circulating “at very low levels,” the World Health Organization’s (WHO) Maria Van Kerkhove said at a recent briefing. 

About 75 cases of AY.4/BA.1 have been reported globally, according to GISAID, an international database of viral sequences, so any uptick in infections that’s being registered in Europe and

elsewhere is “very, very unlikely to be coming from any deltacron variant,” says Ross Kedl, a professor of immunology and microbiology at the University of Colorado Anschutz School of

Medicine. 

Still, “people are keeping a very close eye on it,” says Richard Kennedy, a professor of medicine and codirector of the Vaccine Research Group at Mayo Clinic. 

The emergence of a hybrid variant, also called a recombinant, was not wholly unexpected given the “intense amount of circulation that we saw with both omicron and delta” during winter, Van

Kerkhove said at a recent press briefing. That’s because recombinants occur when two virus strains (in this case, delta and omicron) infect an individual at the same time. As the viruses

replicate they swap information and “the genetic material recombines to create a new strain,” Kedl explains.