What is deltacron and is it causing more COVID-19 cases?

Admittedly, I went through all five stages of grievance when I first saw a reference to “deltacron,” a coronavirus variant. Another one? I thought, immediately thinking about all the friends I’m gonna have to cancel on.

But wait and take a breath before you reach for your phone. “Deltacron,” or “deltamicron” if you like more syllables in your portmanteaus, might be appearing in the news, but so far it seems to be more bark than bite.

As its unofficial name suggests, it’s a combination of the delta and omicron variants, with a spike protein that’s extremely close to omicron’s and the rest of its genome coming from delta. It could have come from a person who was carrying both delta and omicron; the viruses could have combined in an infected cell, and then that product could have continued to replicate in the infected person.

Viral recombination is to be expected—especially when this virus has gotten to infect so many people. But the phenomenon doesn’t necessarily spell disaster. In this instance, “I don’t think there’s any need for general worry from the population,” said Dr. Amesh Adalja, an infectious disease doctor and senior scholar at the Johns Hopkins Center for Health Security. “I think ‘deltacron’ is more of a clickbait term than actually a real threat that we face. We know that coronaviruses are going to recombine and there [are] going to be recombinant viruses, but there’s no evidence that this is spreading rapidly or poses any major threat.”

The recombinant was identified in samples collected in January. GISAID, an international database recording coronavirus gene sequences, shows that in the months since, it’s only been reported from France, Denmark, Germany, Belgium, and the Netherlands. (Reuters reported that it’s been found in the United States as well.) France has the highest number of reported deltacron cases—a total of 35. Denmark has the second highest number of hits: eight. The European Center for Disease Prevention and Control has it listed as a variant of interest, which is a lower designation than “variant of concern.” The World Health Organization and the US Centers for Disease Control and Prevention don’t even have it listed as a variant of interest.

Fusing delta and omicron “doesn’t give it superpowers,” says Adalja (though research into it is still ongoing). The name makes it sound like it has all of delta’s and omicron’s strengths and none of their weaknesses. But that’s really not the case at all. The fact that it’s a combination of things we’ve seen before is actually a good thing. It’s unlikely to cause more severe disease compared with its origin variants. Given that the spike protein is so similar to that of omicron, “if you’ve got antibodies that work against the omicron spike, there’s no reason they wouldn’t work against the recombinant spike,” said Adalja. Even if the spike protein was derived from delta, we’ve seen that too, and “we know our vaccines are able to protect against serious illness.” This also applies to the antivirals that work against delta and omicron.

Being anxious about a new recombinant or variant is understandable—it’s likely that another tricky variant will come on the scene at some point. Overall, there has been an increase in COVID-19 cases, with Hong Kong in particular experiencing a deadly surge. This trend does not seem to be caused by an entirely new variant, though omicron’s offshoot BA.2 might be partially responsible for an increase in cases in Europe, along with relaxing restrictions. While deltacron seems to be nothing special, the virus in and of itself is still worth being wary of.

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