While experts have largely agreed that the introduction of SARS-CoV-2 on the West Coast likely came from China, the strain that is gaining dominance in parts of the U.S. and elsewhere in the world appears to be one that mutated as it spread in Italy — and researchers say it is more highly contagious than the original Wuhan strain.

Like so many revelations from the scientific community in the last few weeks, the news comes from non-peer-reviewed data and a report that was rushed to publication for reasons of public-health urgency. The 33-page report was published on the site BioRxiv, and it comes from research led by Southern California-based computational biologist Bette Korber.

The most significant new developments, per the LA Times:

• The mutated strain of the virus has different "spikes" on the outside than the original strain.
• Almost as soon as the original strain arrived in New York, the mutated second strain arrived from Europe and quickly took over the local epidemic. Something similar happened in Washington State. (The report didn't look at California.)
• The mutated strain is not necessarily more lethal than the original, but appears more infectious and "successful" from a Darwinian standpoint, which explains why it quickly takes dominance.
• The existence of the two different strains leads to the possibility that people can be infected more than once, and that a vaccine for one may not be effective against the other.
• The report lends credence to the theory that medical experts have had to explain why the outbreaks in California have not been as severe or widespread as those on the East Coast.

Korber has a long history in HIV research, and she oversees the HIV Database and Analysis Project at Los Alamos National Labs, which is a global database of more than 840,000 sequences from publications of the HIV genome. And her team was responsible in 2000 for establishing the likely origin timeframe of the virus in humans, in 1930, based on genetic modeling.

Writing on Facebook as the posted the report, Dr. Korber says, "The story is worrying, as we see a mutated form of the virus very rapidly emerging, and over the month of March becoming the dominant pandemic form... This is hard news, but please don’t only be disheartened by it. Our team at [Los Alamos National Labs] was able to document this mutation and its impact on transmission only because of a massive global effort of clinical people and experimental groups, who make new sequences of the virus (SARS-CoV-2) in their local communities available as quickly as they possibly can."

Echoing what researchers at UCSF recently said about a global project to quickly identify treatments for the disease, Dr. Korber writes, "We cannot afford to be blindsided as we move vaccines and antibodies into clinical testing. Please be encouraged by knowing the global scientific community is on this, and we are cooperating with each other in ways I have never seen … in my 30 years as a scientist."

Update: The Chronicle got quotes from a couple of scientists who suggest that Korber and her team may have leapt to some conclusions that are not supported by their data. Microbiologist Shannon Bennett, the chief of science at San Francisco’s California Academy of Sciences, says, "It’s definitely over-interpreting, making more inferences about this mutation than are justified. They can neither make the claim that it is more transmissible or more severe based on the evidence in this paper."

Meanwhile, Robert Siegel, a professor in the Department of Microbiology and Immunology at Stanford University, tells the paper, "This is a very useful addition to the current information on SARS-CoV2. It combines extensive information from public databases on coronavirus genomics, with an analytical tool for detecting sequence variants of interest."

Related: UCSF Team Identifies 10 Existing Drugs and Compounds to Treat COVID-19