Researchers advise scientists to take caution when studying viral genetics in outbreaks. They claim that erroneous hypotheses on the virus' mutation might have saved Washington from becoming New York.
Late in February, cases of COVID-19 began sprouting around Washington state. Researchers quickly examined the genetics behind the virus in an attempt to further understand the pathogen infecting the residents.
It was initially believed that a person who arrived in Washington coming from Wuhan, China on January 15 might have started the spread of the coronavirus in Washington. Furthermore, the same person was also the first case of contamination identified in the entire United States.
The assumption took part in state officials' decision to impose some of the country's earliest social-distancing measures. However, at this stage when scientists know more about the genetics of circulating SARS-CoV-2 viruses, the initial hypothesis might turn out to be wrong.
Researchers now have access to the full genetic blueprints of more than 25,000 SARS-CoV-2 viruses obtained from patients. With that, a new study suggests that the cases detected in Washington in late February were not associated with the first case in January.
Instead, the Evergreen State's February outbreak was likely caused by further introductions of new SARS-CoV-2 strains. The analysis pins the emerging introduction to February 13, two weeks before the cases became evident.
The new research is a preprint that has not yet been published in a scientific journal or gone through the standard scientific vetting of peer review. Even so, several researchers generally accept the findings of the paper. Moreover, the analysis circulates into a growing stream of cautions and corrections about genetic analyses conducted early in an emerging outbreak.
Genetic Sequences of the Virus
Geneticists can work out how SARS-CoV-2 viruses relate and differ from each other by looking into their genetic sequences. In the process, researchers can also aid in understanding the chains of transmission between individuals. This setback initially caused researchers to suspect that the February COVID-19 cases in Washington state were linked to the first case in January.
In the new study, researchers studied the genetic data gathered since the end of February. Micheal Worobey, the leader of the study, and his team noted that even though the SARS-CoV-2 from the first Washington case, dubbed WA1, is almost identical to the other SARS-CoV-2 viruses found in the state, they differ by two nucleotides.
Furthermore, the authors noted that even with hundreds of genomes sequenced in Washington state, no viruses with genomes identical to WA1 or transitional between it and the outbreak clade had been obtained there.
The team then set up simulations with the latest estimate for SARS-CoV-2's transformative rate. In all their simulations seeded with WA1, none resulted in viral strains likened to the genetic changes seen in the real outbreak viruses. Moreover, the researchers approximated that another case arrived in the state on February 13, with a possible arrival date ranging between February 7 to February 19.
Quick Actions on Social Distancing Pay Off
Although the analysis still needs to be peer-reviewed, other researchers seemingly welcome the general conclusion that new introductions of SARS-CoV-2 likely led to Washington's outbreak and not the original case in January.
Of these accepting researchers belongs Trevor Bedford, the researcher who first speculated that WA1 was the source of the February outbreak in the state. The expert in viral evolution at the Fred Hutchinson Cancer Research Center in Seattle admitted on Twitter that his theory has not held up.
Although initially erroneous, researchers say a silver lining in it is that due to fears of a massive, hidden outbreak, Washington became among the first in the US to initiate constraints on social distancing and gatherings.
