Dealing with the delta variant has proven to be more difficult than hoped. It's more contagious than earlier coronavirus strains. The efficacy of COVID-19 vaccines appears to be lower against delta. But could things get even worse? In this Motley Fool Live video recorded on Aug. 25, Motley Fool contributors Keith Speights and Brian Orelli address a viewer's question about new variants beyond delta that could potentially be on the way.

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Keith Speights: Jim R. asks, "Is there any new iteration of the COVID-19 No yet." I'm assuming Jim is referring to new variants beyond the delta variant, maybe. Do you think maybe that's just the question here?

Brian Orelli: Probably. I think we're beyond delta now, but I don't think the one beyond delta is worse than delta, so I think that's where we're at right now. I'm 99% sure I read that we were beyond delta. They're going by the Greek alphabet, I think so.

Speights: Yeah. There is a lambda variant you don't hear much about. I did see something interesting that, I think this was Moderna's (MRNA 0.89%) president in Moderna's Q2 call, stated that Moderna is concerned about a combination of some of the worst mutations between several of the variants floating around right now.

In fact, he said it could be scary. We can't rule out the possibility that more variants will emerge that are even more contagious than delta. That just remains to be seen.

Orelli: Yeah. I think the biggest issue is going to be variants of delta. I think those will still go by the Greek alphabet. I don't think they'll spin off delta to go someplace else. But I think the variants of delta are probably the most scary because it's going to take delta and then go even worse.

The reason why they get worse, in theory, is because there's a selection pressure. If there's a mutation as the virus is replicating in one person, if there is a mutation that makes it more virulent, which means it can replicate faster and infect faster, produce more virus faster, than that will be selected for because that one will be able to replicate faster.

Therefore, when it gets to next host, it'll be replicating faster than the other viruses that get transferred as well, then eventually it gets selected for because the rate of infection is improved and so then that becomes the predominant virus in that area.