This transmission electron microscope image shows SARS-CoV-2 – also known as 2019-nCoV, the virus that causes COVID-19. isolated from a patient in the US leaking from the surface of cells grown in the laboratory.
Even if global Covid-19 infections decline globally, leading US health officials are warning of a wave of infections to come as new, more contagious, and potentially deadly variants of the virus emerge in the US.
Scientists are not surprised by the emergence of the new variants and have repeated that the vaccines currently available should continue to work against them – albeit slightly less effective than against the original "wild" strain. However, US health officials and infectious disease experts fear that these highly contagious variants, particularly strain B.1.1.7 found in the UK, could reverse the current downward trend in infections in the US and delay the country's recovery from the pandemic.
"I think we should assume that the next wave of case growth, as far as we have it, will happen with B.1.1.7 and I think everyone needs to be even more careful." Andy Slavitt, Senior Advisor to the White House Covid-19, told MSNBC last week. "It's nice to see the number of cases go down, but it could be misleading."
Why viruses mutate
As the coronavirus spreads, it makes large numbers of copies of itself, and each version is a little different from the previous one, experts say. SARS-CoV-2, the virus that causes Covid-19, has had many ways to spread and replicate. The more people infected, the more likely problematic mutations become.
The three main "variants of concern" on the verge of US officials were first identified in the UK, South Africa and Brazil. Variant B.1.1.7, first presented in Great Britain, is multiplying rapidly in the USA and, according to a study by the US Centers for Disease Control and Prevention, is expected to become the dominant variety in the country in January by March.
By mutating, the virus is simply trying to "get to the next host and get more out of itself," said Dr. Adam Lauring, an infectious disease expert at the University of Michigan at Ann Arbor, in an interview with the JAMA network on Feb.4. Like other coronaviruses, SARS-CoV-2 tends to mutate more slowly than other viruses like the flu because it has a "proofreading" enzyme that will fix some of the changes when it replicates.
In other cases, "escape mutations" allow the virus to adapt to "selective pressures" when the virus encounters a population that already has some level of immunity to the virus, whether through prior infection, vaccination, or antibody treatment that limits it Ability to spread, but does not stop it.
"You can imagine trying new solutions," said Lauring. "Either that mutation will make you a better virus or a worse one, and then you have choice. Survival of the fittest because there is no better term."
Research shows that more worrisome virus mutations could come from people with compromised immune systems as it takes their bodies longer to respond to and clear the virus, giving it more time to figure us out and mutate, said Dr. Dennis Burton, chairman of the Scripps Research Institute for Immunology and Microbiology.
"If someone has the virus and clears it up in a couple of days, you have little chance of mutating," Burton told CNBC in a phone interview. "But if someone has the virus like an immunocompromised person and has harbored the virus for weeks, it will have a lot more chance of mutating."
Why are some worse than others?
Few variants become a public health problem, according to infectious disease experts. These variants are usually easier to spread, cause more serious illnesses in infected people, or elude some protection against vaccines and antibodies.
CDC director Dr. Rochelle Walensky told JAMA on Wednesday that variant B.1.1.7 is considered to be about 50% more transmissible and early data suggests it could be up to 50% more virulent or deadly.
There is also evidence that people infected with previous strains of the virus could be re-infected with variant B.1.351 found in South Africa, Walensky wrote in a JAMA position with White House Chief Medical Officer Dr. Anthony Fauci, and Dr. Henry Walke. the CDC's Covid Incident Manager.
SARS-CoV-2 is a coronavirus, a large family of viruses called "because of the crown-like tips on their surfaces", according to the CDC. Researchers monitor these spikes, or the S protein, for mutations as they can allow the virus to attach to cells more easily or increase the amount of virus a person gives off.
The S-protein has a so-called "receptor binding domain" that acts like the "hand of the tip" that captures the so-called ACE2 receptor on human cells. Dr. Daniel Griffin, head of infectious diseases at ProHEALTH, told CNBC.
Changes to the S protein could be an issue as these spikes were aimed at neutralizing antibodies that fight Covid-19 and are created through natural infection or vaccination, Griffin said. They could also affect the performance of monoclonal antibody therapies, which prevent people from developing serious diseases.
For example, variant B.1.1.7, identified for the first time in Great Britain, has several different mutations according to the CDC. One of the key mutations, N501Y, is an alteration in the spike protein that scientists believe helps the virus attach to cells more easily.
The same key N501Y mutation developed separately in the B.1.351 variant identified in South Africa and in the P.1 variant in Brazil. Both strains have also developed another mutation in their spike proteins known as E484K.
The CDC warns that this mutation, now identified in some B.1.1.7 cases, may be resistant to antibody drug therapies, and early studies show that it may reduce the effectiveness of some vaccines.
"This is the one that really worries me," Griffin told CNBC, referring to the E484K mutation.
What this means for vaccines
Although the vaccines against the variants have still been shown to be effective, there is concern that the B.1.351 strain may present some challenges.
Large clinical trials by Johnson and Johnson and Novavax reported that their vaccines had penetrated in late January Effectiveness in the test in South Africa, where the variant first appeared. Novavax said its vaccine was only 49% effective among 49 Covid-19 cases in South Africa, and J&J said its vaccine was 57% effective in preventing symptomatic Covid-19.
World Health Organization vaccination director Kate O'Brien said Thursday that these results don't offer much certainty as the number of cases in the South African trial arms is low.
"We are still in the early stages of interpreting the evidence, and again the most important thing is to get more information about what is actually happening in relation to diseases," O & # 39; Brien said at a press conference. "In general, we see that the vaccines retain their effectiveness against disease, albeit at a lower level in environments without the prevalent variants."
Pfizer and Moderna
Clinical studies from Pfizer-BioNTech and Moderna were conducted before the variants emerged. Scientists have therefore carried out laboratory tests to determine how well blood samples from people who have already been vaccinated react to virus variants with the key mutations constructed in the laboratory.
These studies, in which it was examined whether the sera in the blood neutralize the virus and prevent its replication, showed a reduction in performance when tested against variant B.1.351. This "indicates that currently used vaccines could be less effective in preventing infections because of this variant," wrote Walensky, Fauci and Walke from their point of view.
However, your body's ability to fight off the virus may depend on more than just neutralizing antibodies, including T and B cells, which can help fight the virus but are not measured in the early laboratory tests, Lauring told JAMA.
The good news is that Pfizer and Moderna vaccines had such a high rate of effectiveness even in previous studies – around 95%. So there is a pillow that allows for a drop in performance while it is considered effective by doctors, experts say. The gunshots were also shown to protect against serious illness that would result in hospitalization or death.
Both Pfizer and Moderna have already announced that they are working on a booster shot for their vaccines that will better withstand strain B.1.351.
Find the mutations
The B.1.1.7 variant was first identified in the United Kingdom in December, but is believed to have surfaced sometime in September. Many experts have recognized the UK's ability to perform large-scale genome sequencing to find the variant.
Genome sequencing is a laboratory technique that breaks down the virus' genetic code and allows researchers to monitor how it changes over time and understand how those changes could affect it, according to the CDC.
According to the latest data from the CDC, there are now 1,661 documented Covid-19 cases with variant B.1.1.7, 22 cases with variant B.1.351 and 5 cases with variant P.1 in the USA. Officials acknowledge that the US is sequencing a small fraction of the cases and the spread of the variants is likely to be far wider. However, the federal government has recently attempted to increase the number of samples sequenced per week to identify these variants and other mutations that may develop domestically.
The CDC has partnered with public health and trade laboratories to rapidly improve genome sequencing in the country. Walensky told JAMA on Wednesday that the US was sequencing only 250 samples a week in January, which has since grown "by the thousands". She added, "We're not where we need to be."
Dr. Ilhem Messaoudi, the director of the University of California at the Irvine Center for Virus Research, said the process could be time-consuming and labor-intensive, but newly emerging strains would be overlooked if the laboratories did not sequence a certain percentage of all positive Covid-19. 19 test results to find the new mutations, she said.
"Now we're trying to catch up," Messaoudi said in a telephone interview with CNBC. "We say, 'Let's go back and see if we have that.'"
Masks, social distancing
The fast-spreading variants renew the importance of suppressing the spread of the coronavirus through public health measures like wearing masks, social distancing and hand hygiene to prevent further mutations and give countries time to deploy life-saving vaccines.
Coronavirus variants aren't just a problem for the United States, however. If the virus is spread in other parts of the world that are not vaccinated, it could lead to mutations that could threaten the widely used vaccines in other countries, the CDC chief warned on Wednesday.
At some point, the whole world has to build immunity to the virus, otherwise the variants will continue to be a problem, Burton told CNBC.
"Sooner or later, variants will be everywhere if they have a big advantage," said Burton. "It's a global problem, it's not just a problem for one country."