How Coronavirus works in North America and Europe
A new study combines the evolutionary genome from coronavirus samples with computer-simulated disease and detailed travel profiles to recreate the worldwide spread of coronavirus in unprecedented detail.
Published in the journal Science, the results suggest a long missed opportunity as in-depth inspection and contact tracing may have prevented SARS-CoV-2 from being established in North America. and Europe.
The paper also challenges proposals to link the earliest known cases of COVID-19 per continent in January to outbreaks discovered a few weeks later, while providing insights. Value that can inform public health responses and help predict and prevent future COVID-19 outbreaks and zoonotic diseases.
Researcher Michael Worobey of the University of Arizona said: “Our aspiration is to develop and apply powerful new technology to conduct a definitive analysis of how pandemics break out in space and time above. Global”. in the US, Belgium, Canada and UK “Before, there was a lot of possibilities floating around a mess of science, social media, and the unprecedented number of pre-printed publications still awaiting evaluation. of colleagues. ”
The team based their analysis on results from the virus’s genome sequencing efforts, which began as soon as the virus was identified. These efforts rapidly evolved into an unprecedented worldwide effort of scale and speed and has yielded tens of thousands of genome sequences, which are widely available in the database.
Contrary to popular stories, the first recorded cases of infected people travel from China to the US. and the researchers found that Europe did not break out into snow on the continent.
Instead, rapid and decisive measures to track down and prevent early virus intrusions have been successful and will be seen as the model response that directs future actions and policies. of government and public health agencies, the study’s authors concluded.
How the virus arrived in the United States and Europe
A Chinese citizen flying to Seattle from Wuhan, China on January 1 becomes the first patient in the United States believed to be infected with a new type of coronavirus and the first to have the SARS-CoV gene sequence -2. This patient is designated ‘WA1.’ It was not until six weeks later that a number of other cases were discovered in Washington state.
“And while all the time passed, everyone was drowning in darkness and wondering, ‘What’s going on?'” Said Worobey. “We hope we’re okay, we hope there are no other cases, and then it became clear, from a remarkable community virus sampling program in Seattle, that there are many schools. are more fused in Washington and they are genetically very similar to WA1. ”
Worobey and his colleagues tested the popular hypothesis that the WA1 patient had set up an undetected transmission group for six weeks. Although the genomes sampled in February and March have similarities with WA1, they are so different that the idea of WA1 causing the next outbreak is highly unlikely, they identified. The findings of researchers indicate that the leap from China to the US could occur around or around February 1 instead.
The results also raise speculations that this outbreak, the earliest major transmission cluster in the United States, could be initiated indirectly by spreading the virus from China to British Columbia, Canada, right up front. North Washington State, and then Canada to the United States Many of the SARS-CoV-2 genomes announced by the British Columbia Center for Disease Control appear to be the ancestors of virus variants sampled in Washington State, for clearly see the Canadian origin of the United States. Disease. However, current research has revealed sequence errors in those genomes, thus eliminating this scenario.
Instead, the new study implies a source directly from China in the United States. outbreak, around the same time the United States government implemented a travel ban on tourists from China in early February. The nationality of the US “case index” outbreak can not be known with certainty because tens of thousands of US citizens and visa holders have traveled from China to the United States even after the order. prohibition is in effect.
A similar scenario marks the first introduction of coronavirus into Europe. In January. 20, an employee of an auto supply company in Bavaria, Germany, flew in for a business meeting from Shanghai, China, accidentally brought the virus, eventually leading to infection to 16 colleagues. In that case, the impressive response of the rapid test and isolation prevented further outbreaks, the study concludes. Contrary to speculation, this German outbreak was not the source of the outbreak in Northern Italy, but eventually spread across Europe and eventually to New York City and the rest of the United States.
The authors also point out that this China-to-US pathway caused the East Coast outbreak to occur slightly later in February than the move from China to the United States by The withdrawal caused an outbreak in Washington. The Washington cluster also predated small community clusters in February in California, making it the earliest cluster anywhere in North America.
Initial control work
The authors said in-depth interventions, including testing, exposure monitoring, quarantine measures, and a high level of compliance by infected people, who reported symptoms of they sent medical services and quarantined themselves in a timely manner, helping Germany and the Seattle area prevent the January outbreak.
“We believe those measures have led to a situation where the first sparks can be successfully extinguished, stopping the spread to the community,” Worobey said. “This tells us that the measures taken in those cases are highly effective and should serve as a blueprint for future reactions to potentially high-risk diseases. outbreaks into a pandemic around the world. ”
To recreate the outbreak of the pandemic, scientists ran computer programs that carefully simulated the epidemiology and evolution of the virus, in other words, the way SARS-CoV-2 spread and mutated. turn over time.
“This allows us to re-run the tapes of how the disease broke out, and then test the scenarios that appeared in the simulation against the models we see in practice,” Worobey said.
“In the case of Washington, we might ask, ‘What if that WA1 patient who arrived in the United States on January 15 actually started that outbreak?’ Well, if he does that, and you run that plague over and over, and then sample the infected patient from that plague and evolve the virus that way, do you get a model like what? do we see it in reality? The answer is no, “he said.
He said: “If you seed the initial outbreak in Italy with the German one, do you see the pattern you got in the evolutionary data? And the answer, again, is no.” he said.
“By rerunning the introduction of SARS-CoV-2 into the US and Europe through simulations, we have shown that early viral imports are very unlikely,” said co-author Joel Wertheim. The first recorded entry into these areas has resulted in effective transmission clusters. of the University of California, San Diego. “Molecular epidemiological analyzes are extremely powerful in revealing transmission patterns of SARS-CoV-2.”
Other methods are then combined with data from the virtual services, giving exceptionally detailed and quantitative results.
Co-author Marc Suchard said: “The cornerstone of this work is our new tool that combines detailed travel history and phylogenetic information, creating a kind of ‘family tree’ of how The different genomes of the virus sampled from infected individuals are related to each other “by the University of California, Los Angeles.” More accurate evolutionary reproduction from these tools provides a step forward. It’s important to understand how SARS-CoV-2 spread globally in such a short time. ”
“We are only studying the short term evolution of this virus, so it doesn’t have much time to accumulate many mutations,” said co-author Philippe Lemey at Leuven University, Belgium. “Add to that the uneven sampling of genomes from different regions of the world and there are obviously huge benefits to be gained from integrating different information sources, combining replication. genome with additional methods such as flight record and total COVID -19 cases in different global regions in January and February. ”
“Our research shows that when you do early intervention and detection well, it can have a big impact both on preventing pandemics and controlling them as they progress,” says Worobey. “While the plague is finally over, there are early victories that show us the way forward: Comprehensive testing and case determination are a powerful weapon.”