Once again, some of the latest headlines about the ongoing COVID-19 pandemic are alarming: Another variant of the virus is now on the rise in the United States.“Although this is concerning, it’s not surprising – we’ve been watching for this and more or less expecting it,” explains microbiologist and pathologist Daniel Rhoads, MD. As scientists and public health experts work to better understand what impact these new variants will have on the course of the pandemic, here’s what we do and don’t know so far.

The Delta Variant

The variant now causing concern around the world is the “delta” variant. Experts say a particular strain of the delta variant (a mutated version of the variant that is more infectious) is responsible for the recent surge of cases in the United Kingdom.

This strain, B.1.617.2, is currently the dominant one in the U.K. and is labeled as a “variant of concern” by the World Health Organization (WHO). The main reason for the concern: Experts believe it to be up to 60% more transmissible than the original strain of COVID-19.

While research is ongoing, early data also suggests that this particular variant could be one of the driving forces behind the enormous surge in cases – and, subsequently, COVID-19 deaths – in India in the spring.

In the United States, the Centers for Disease Prevention and Control (CDC) recently classified the delta variant as a “variant of concern” due to an ongoing increase of cases. In mid-May, it accounted for only 2.5% of U.S. cases but by mid-June, that number increased to at least 6%, according to the National Institute of Health.

How Does A Virus Mutate?

While the idea of a virus mutating might sound scary, it’s actually quite normal. Viruses mutate constantly. This is especially true of viruses that contain RNA as their genetic material, such as coronaviruses and influenza viruses.

All viruses are made up of a bundle of genetic material (either DNA or RNA) that’s covered by a protective coating of proteins. Once a virus gets into your body – usually through your mouth or nose – it latches onto one of your cells. The virus’s DNA or RNA then enters your cell, where it can make copies of itself that go off and infect other cells. If the virus can copy itself and hijack enough of your cells without being wiped out by your immune system, that’s how you get sick.

Every now and then, an error occurs during the virus’s copying process. That’s a mutation.

Most of the time, mutations are so small that they don’t significantly affect how the virus works, or they make the virus weaker, Dr. Rhoads says. But occasionally, a mutation helps the virus copy itself or get into our cells more easily.

“If these advantageous genetic mistakes are included when the virus replicates, they’re passed on and eventually become part of the virus’s normal genome,” Dr. Rhoads explains. We can see these mutations accumulate over time, and that’s how we get new variants of a virus strain.

If you get confused about strains, variants and mutations, think of it this way: New variants of a virus strain emerge through the process of mutation. In the media, the words strain and variant are often used interchangeably.

What Do We Know About Other COVID-19 Variants?

The delta variant is just the latest one to cause concern in the U.S. as it spreads across the globe. Earlier this year, more infectious variants from the U.K., South Africa and Brazil made headlines as they became more dominant in different parts of the world.

Each has its own set of mutations, but they all contain small changes to parts of the spike protein that helps the coronavirus attach to our cells.

“This is concerning, because it means the virus could spread more easily,” Dr. Rhoads says.

It’s hard to measure exactly how much of an impact new variants initially have on the pandemic since many factors contribute to how quickly a virus spreads – including human behaviors.

But those concerns over the new delta variant are for good reason. The U.K. variant that alarmed experts in the U.S. at the beginning of the year, called B.1.1.7 or “alpha,” now accounts for nearly 70% of all U.S. cases. And the variant from Brazil, P.1, accounts for over 11% of all U.S. Cases. The CDC considers both “variants of concern,” notes Dr. Rhoads.

There is good news, though, as a study out of England showed that the Pfizer vaccine was still highly effective (88%) against symptomatic disease from the delta variant. “These new variants can also still be detected with our current tests, so that’s one thing that should be reassuring,” Dr. Rhoads adds.

The Takeaway? Stay Vigilant And Get Vaccinated

In the end, the shape-shifting nature of the coronavirus (and all viruses) is something that experts across the world are keeping a close eye on, but it’s not something you should expect to change the course of the pandemic overnight.

However, the contagiousness of the newer variants is all the more reason to stay careful even as most states roll back social distancing guidelines. Only half of U.S. adults are fully vaccinated but, in many states, that number remains below 50%.

“These new waves of infections show that the pandemic is not close to being over yet,” Dr. Rhoads says. “At this time, vaccination has proven to be our most effective tool, and vaccines are readily available for many children and adults in the U.S. Vaccinations are our best defense against these emerging mutations.”