New, more contagious strains of COVID-19 may be spreading quickly

Infectious disease expert answers questions about what we do and don’t know


Two fast-spreading COVID-19 variants discovered in recent months have health officials concerned worldwide, especially as the pandemic rages worse than ever in many places, including California. 

Fast-spreading variants of COVID-19 are putting even more strain on hospitals trying to help them.
Fast-spreading variants of COVID-19 are putting even more strain on hospitals trying to help them.

The more widespread of the coronavirus variants was first identified in the United Kingdom in September. It has now been found in at least 40 countries, according to the World Health Organization. The Centers for Disease Control and Prevention (CDC) says it has been reported in at least 10 states. 

The other variant was discovered in South Africa and is in at least six countries. To scientists, the UK strain is known as B.1.1.7. The South Africa variant is 501Y.V2. 

Experts are still learning about these COVID-19 variants, but researchers believe both are more contagious. Dean Blumberg, chief of pediatric infectious diseases at UC Davis Children’s Hospital helps sort out what is known and what questions need to be answered. 

How much more contagious are the new COVID-19 strains?

Both variants appear to have become the main strain in the regions where they originated, which demonstrates how easily they are spread. 

“Most of the evidence comes from the UK, where they found the rate of transmission is higher in places where the new strain is prevalent,” Blumberg said. “Exactly how much faster it spreads is still unclear. Most of the estimates I see say it is 40% to 70% more contagious. Most scientists are using the 70% estimate.” 

Why are the new strains of COVID-19 more contagious?

 The UK variant has 17 mutations – mutations are common in all viruses but most don’t affect their function. Eight of the mutations are in the spike protein, which is what attaches to human cells. 

“There is no evidence that the new strains have any new symptoms or make people sicker … but if more people get sick because it’s more contagious, more people will die.”

— Dean Blumberg

“Those mutations change the shape of the spike protein. That helps the virus bind more strongly to our cells,” Blumberg said. 

In addition, the variant appears to get inside our cells more easily. 

“It binds better, gets inside better and multiplies better, so someone infected will have a higher concentration of the coronavirus,” Blumberg said. “The higher concentration is another reason why people with the new strain are more contagious. If you’re a virus, it’s a better design for surviving and spreading.”

Are the new COVID-19 variants more deadly? Do they make people sicker?

“There is no evidence that the new strains have any new symptoms or make people sicker,” Blumberg said. “The case fatality rate won’t change, but if more people get sick because it’s more contagious, more people will die.” 

In addition, more cases mean more people will be hospitalized, hospitals will be under greater pressure, and in some regions, people with other serious illnesses and injuries will suffer, too. 

“That won’t happen at UC Davis Health,” Blumberg said. “But with the surges, it’s happening around the country. A more contagious strain is going to mean more deaths if we don’t contain it.” 

Are the vaccines effective against the new COVID-19 variants?

Pfizer and BioNTech announced that a preliminary study shows their vaccine is effective against the mutation in the spike protein in the two variants. 

If people get vaccinated as soon as they are eligible, COVID-19 can be controlled faster and it will mutate less.

And experts believe the Moderna vaccines will also be effective against the new coronavirus strains. More research is ongoing. 

“Like with other vaccines, we don’t have just one antibody that forms, we have multiple and different antibodies,” Blumberg said. “The spike protein is a complicated protein. The antibodies attack the spike protein in several areas, so if one part changes, there are other areas we can have an immune response against.” 

He said antibodies from people previously infected with other COVID-19 strains appear to have neutralized the new variants effectively. 

“It doesn’t appear that they’ll be evading the vaccine-induced immunity,” Blumberg said. 

In addition, Pfizer/BioNTech and Moderna, the manufacturers of the vaccines currently approved in the U.S., have said they can change the vaccine to adapt to new strains in as little as six weeks. 

“It’s the nature of the platform they developed,” Blumberg said. “It’s like a plug and play system. They could easily update these vaccines. It’s even easier than updating a flu vaccine.” 

Will the vaccines work on all new strains?

There is more concern about the variant that originated in South Africa because it has mutations that seem to help it hide from some antibodies, which could mean current vaccines would be less effective against it. 

“It doesn’t appear that they’ll be evading the vaccine-induced immunity.”

— Dean Blumberg

“That is the strain we’re more worried about,” Blumberg said. “The hope is that if the vaccine doesn’t match perfectly, it will still provide partial protection (which would be similar to some seasons of the flu vaccine). That means some people may be protected and others who did get infected with that strain of COVID-19 after being vaccinated would have a case that is less severe.” 

Pfizer has said it is studying the effectiveness of its vaccine against this mutation. 

Is treatment any different for the new COVID-19 strains?

Generally, doctors have had the same success treating patients with any of the variants. 

“The new strains do not appear to be inherently resistant to remdesivir or any of the effective treatments,” Blumberg said. 

Can tests detect if someone with one of the new variants is COVID-19 positive?

Most high-quality PCR tests can give patients a yes or no answer about whether they are COVID-19 positive with all strains so far, but they can’t distinguish what strain a patient has. 

“All of the tests currently offered at UC Davis Health can detect the new SARS-CoV-2 variant,” said Nam Tran, professor of laboratory medicine and a member of the California COVID-19 Testing Task Force. “However, there are presently no commercial PCR assays that can differentiate the new variant vs. existing variants. The only way is by sequencing the genetic material in the coronavirus, which we can have performed via the state Department of Public Health (CDPH) Laboratory in Richmond.” 

Experts are hopeful high-quality antigen tests – which are often used for rapid testing – can also tell whether a patient is positive for COVID 19 with the new variants. Because there is a range of quality among antigen tests, it may depend on the test. UC Davis Health specialists are currently evaluating one antigen test for effectiveness with the new strains. 

Read more about the COVID-19 variants and testing from UC Davis Health Pathology and Laboratory Medicine experts. 

How widespread are the new variants in the U.S.?

That is uncertain. The CDC is monitoring cases but says current information likely undercounts the cases of the variants. 

“Everything we do to prevent the spread of COVID-19 now will slow the new variant.”

— Dean Blumberg

“We have reports of it in a few states, including California,” Blumberg said. “But we aren’t sequencing nearly as many samples as they do in the UK, so we really don’t know much about what strains are circulating.”

The U.S. has no large-scale, nationwide system for sequencing the virus to look for new mutations. The New York Times reported that Britain has sequenced more than 200,000 coronavirus genomes out of its 2.8 million COVID-19 positive cases. The U.S., which has had more than 21.4 million cases, has only sequenced about 58,000 genomes.

“We need to know what’s here,” Blumberg said. “If we start looking for it, we’ll likely find it.”  

Does this mean COVID-19 precautions like masking, social distancing and washing your hands are even more important?

“Everything we do to prevent the spread of COVID-19 now will slow the new variant,” Blumberg said. 

And slowing any variant of COVID-19 means reducing the likelihood of other, hard-to-fight variants developing. 

 “That’s yet another reason why we have to practice all the cautions,” he said. “And it’s why everyone should get vaccinated as soon as it’s available to them. We don’t want to give the virus more chances to mutate inside us. The faster we stamp out the pandemic, the less we have to worry about new mutations.”