When Omicron Met Delta

By Amichai Perlman, PhD, PharmD
Medically reviewed checkmarkMedically reviewed
March 29, 2022

Have you heard the news about the new “stealth” subvariant of Omicron, or about Deltacron? Should we be worried, or is this just fear-mongering?

The COVID-pandemic has pushed several scientific areas into the limelight, and forced all to brush up and remember our biology 101. Preliminary scientific findings which in the past were mainly communicated among virologists, immunologists, and epidemiologists, have become regular features in prime-time media. 

So we’ve come to learn that as coronaviruses replicate en mass, some of them incur small changes to their genes. This sometimes results in a genetically altered version of the virus – or a variant. 

In some cases, the altered genes result in changes that are concerning, i.e. “variants of concern”. The concern with such variants is that they may spread more easily, cause more severe disease, or compromise the efficacy of available vaccinations, tests, or treatments. Some variants initially suspected to be of concern did indeed have some of these qualities—most recently Omicron—while others did not. 

So What’s The Deal With The New Variants?

Variants currently featured in the media include the BA.2 “stealth variant” and “Deltacron”. 

BA.2 is one of a few Omicron sub-variants. It is essentially still regarded as “Omicron”, and is likewise a “variant of concern” due to its enhanced contagiousness. In addition, studies have now established that people who have recovered from the previous Omicron variant (BA.1) can experience reinfection within BA.2 within a few weeks of recovery. This risk of reinfection is however low.

“Deltacron” is a variant combining genetic code from the Delta and Omicron variants. In contrast to previous reports of Deltacron, which turned out to be the result of a lab error, recent reports have indeed documented variants that combine generic codes from previous variants. Reported variants include combinations of Delta and Omicron and combinations of the two sub-variants of Omicron. 

How Did Deltacron Arise?

The combination of variants is termed “viral recombination”. This occurs when a person is infected with two variants of the virus which co-infect the same host cell. As the variants replicate within the host cell, they exchange segments of their genes and new variants can arise. Recombination has been documented with many viruses, including with coinfection of influenza virus strains, herpes, and others. The recent large waves of Delta and Omicron have likewise resulted in some cases of co-infection leading to viral recombination – hence “Deltacron”. 

Why Are We Only Hearing About Viral Recombinants Now?

Coronavirus species in general have been known to undergo recombination. The current SARS-Cov2 coronavirus is no exception. A recently published analysis of viral genetic data collected over a year ago identified several hundred cases of recombination, and estimated that “at most 0.2–2.5 percent of circulating viruses in the USA and UK are recombinant”. There may currently be an increase in the detection of such variants due to increased genetic sequencing, increased spread of the virus, and due to the qualities of recent variants which can be differentiated relatively easily using some routine testing procedures even without genetic sequencing. 

How Concerned Should We Be?

There are many documented variations of the coronavirus, most have no clinical significance. There is currently no indication that the recombinant variants, such as Deltacron, are variants of concern. Like all variants, these variants also warrant monitoring. They may prove to be significant, however, most variants do not. 

While there is currently no indication that the recombinant variants featured in the news are concerning, the COVID-19 pandemic is still with us and warrants responsible precautions regardless. In addition, as described above, BA.2 is a subvariant of Omicron. It is designated as a variant of concern and accounts for a growing proportion of COVID-19 cases in the US. Being up-to-date on vaccination and boosters has been proven beyond doubt to significantly reduce the risk of severe COVID-19 from all variants to date. Additional measures of precaution, such as masking, testing, and limiting large indoor gatherings, should also be considered—depending on the level of COVID-19 in your community, and the level of your personal risk and those around you. Since variants arise from mutation and recombination of viruses within host cells – these measures are also the best approach to reduce the risk of new variants.

K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.

Amichai Perlman, PhD, PharmD

Dr. Perlman is a clinical pharmacist and pharmacoepidemiologist, with over 10 years of experience advising patients and clinicians on medication use, personalization, and safety. He has extensively published peer-reviewed research addressing medication safety.