The coronavirus is mutating as it spreads across the planet. The unanswered question is how different these strains are and whether they're more dangerous.
SAN FRANCISCO – The coronavirus is mutating as it spreads across the planet. A strain that may first have appeared in Europe is becoming dominant in many areas even as new ones appear. The unanswered question is how the strains differ and whether they cause additional, and more severe, illnesses.
Several studies identified mutations of the original SARS-CoV-2 virus that emerged in China and causes COVID-19. The strains are very similar but represent slight changes in the virus's makeup.
"That could explain why we're seeing such different outcomes between San Francisco and New York City," said Alan Wu, a professor of laboratory medicine at the University of California-San Francisco's School of Medicine and chief of the clinical chemistry laboratory at Zuckerberg San Francisco General Hospital.
"Everybody talks about the SARS-CoV-2 virus as if it's one thing. It may be more of a problem," said Dr. Greg Poland, director of the Mayo Clinic's Vaccine Research Group.
All viruses mutate, especially RNA viruses such as SARS-CoV-2, Poland said. What's important is whether there's going to be a clinical significance, he said.
A study posted April 30 from Los Alamos National Laboratory found 14 mutations of virus circulating and warned that several had characteristics that could make them more infective. Another paper found several mutations of the virus.
Wu cautioned that it's too early to draw hard and fast conclusions before there's enough data to base them on.
"It's a lot more complicated than either of these two papers suggests," he said. "Lots of labs are doing the research, but they haven't yet published their findings."
Initial results of an in-depth COVID-19 testing program in a small neighborhood in San Francisco published Monday found 2.1% of residents were positive for coronavirus and more than half had no symptoms.
Wu's hospital, which sees a high percentage of poor and underserved patients, has had two deaths and put about 100 people on artificial breathing machines because of COVID-19. New York City has seen more than 13,700 deaths, according to the city's health department.
Though New York's overall population is much larger – 8 million versus 880,000 in San Francisco – the difference is striking.
"How does that happen? It's not just density, San Francisco is the second most dense city in the nation after New York," Wu said.
In New York, 80% to 90% of patients on ventilators died.
"I would love to say it's only that we did things better, but the infection and survival rates between New York and San Francisco are night and day," he said.Are COVID-19 mutations driving the difference?
Labs are busy looking to see whether the mutations partly explain how the disease can be mild in some areas and so deadly in others.
There's evidence that different strains are circulating.
Research conducted at the Icahn School of Medicine at Mount Sinai in New York City found the variant of the virus that arrived in New York mainly came from Europe and was a mutation of one that initially arose in China.
The strain on the West Coast, which appeared in Seattle and San Francisco, is more closely linked to a variant from the Chinese city of Wuhan.
To make things more complicated, researchers at Cambridge University in England found three distinct variants of SARS-CoV-2. They called the first to appear Type A. A second variant, Type B, arose from it and became the majority form found in China. That mutated into several other types, including Type C, the major strain found in Europe.
Several papers reported multiple mutations, though whether they are more infectious or deadly isn't known. Tracking the various trains is difficult because many papers identify variants by different names.
A group at Los Alamos National Laboratory identified 14 different strains of the virus, at least one of which appeared more easily transmissible than the original.
The D614G mutation described by researchers was first seen in Europe in early March, and by early April, its frequency was increasing. When it appeared in a new area, in many cases, it became the dominant form in only a few weeks, the researchers found.
Both the original and the new strain circulated in the English town of Sheffield, and extensive testing there found that although having the mutated strain didn't correlate to a higher chance of being hospitalized, patients did seem to have higher viral loads. Higher levels of the virus in the body are typically associated with worse outcomes.
One concern is that if the virus mutates too far from the versions circulating, it could affect vaccine production. A vaccine could, in essence, create an antibody that is not the virus that is circulating.
"Next fall, the vaccine might give you some immunity or no immunity," Poland said.
Another report, from researchers in China, found at least two major SARS-CoV-2 strains circulating there, and one was more common than the other, which could mean it was better able to adapt.
Labs are working to analyze the genetic differences between the various strains circulating in the world to see whether the levels of sickness and death can in part be explained by genetic differences in the virus itself.
"Answers will come soon," Wu said. “They just haven’t had time yet to publish their findings.”
Contributing: Grace Hauck
SEARCHABLE MAP: Coronavirus death rates and cases for every US county: https://interactives.courier-journal.com/projects/cv19/map/
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