A new study has shown that early infection control interventions such as intensive contact tracing helped to stamp out COVID-19 infections in Europe before they spread.
A new study carried out by an interdisciplinary team of scientists from 13 research institutions in the US, Belgium, Canada and the UK has combined evolutionary genomics from COVID-19 samples with computer-simulated epidemics and detailed travel records in order to reconstruct the spread of the virus across the world in unprecedented detail.
The results have been published in the journal Science suggest an shows that in both the United States and in Europe, sustained transmission networks became established only after separate introductions of the virus that went undetected.
The importance of contact tracing
The paper challenges suggestions that linked the earliest known cases of COVID-19 on the continent in January to outbreaks detected weeks later. It provides valuable insights that could inform public health response and help with anticipating and preventing future outbreaks of COVID-19 and other zoonotic diseases.
University of Arizona researcher Michael Worobey, who led the team, said: “Our aspiration was to develop and apply powerful new technology to conduct a definitive analysis of how the pandemic unfolded in space and time, across the globe. Before, there were lots of possibilities floating around in a mish-mash of science, social media and an unprecedented number of preprint publications still awaiting peer review.”
The team based their analysis on results from viral genome sequencing efforts, which began immediately after the virus was identified and highlights that the first documented arrivals on the continent did not actually snowball into outbreaks, but instead tracing and contacting measures were successful.
Controlling an outbreak of COVID-19 in Europe
The COVID-19 virus was brought to Europe on 20 January 2020 when an individual travelling to Europe from Shanghai, China infected 16 of their co-workers. According to the study, an impressive response of rapid testing and isolation prevented the outbreak from spreading any further, the study concludes. Contrary to speculation, this German outbreak was not the source of the outbreak in Northern Italy that eventually spread widely across Europe.
The authors also show that this China-to-Italy-US dispersal route ignited transmission clusters on the East Coast slightly later in February. Intensive interventions such as testing, contacting tracing, and isolation that were implemented in a timely manner and helped to contain the outbreak.
“We believe that those measures resulted in a situation where the first sparks could successfully be stamped out, preventing further spread into the community,” Worobey said. “What this tells us is that the measures taken in those cases are highly effective and should serve as a blueprint for future responses to emerging diseases that have the potential to escalate into worldwide pandemics.”
The scientists ran computer programs that carefully simulated the epidemiology and evolution of the virus. “This allowed us to re-run the tape of how the epidemic unfolded, over and over again, and then check the scenarios that emerge in the simulations against the patterns we see in reality,” Worobey said.
“In the Washington case, we can ask, ‘What if that patient WA1 who arrived in the US on 12 January, 2020 really did start that outbreak?’ Well, if he did, and you re-run that epidemic over and over and over, and then sample infected patients from that epidemic and evolve the virus in that way, do you get a pattern that looks like what we see in reality? And the answer was no,” he said.
“If you seed that early Italian outbreak with the one in Germany, do you see the pattern that you get in the evolutionary data? And the answer, again, is no.” Co-author Joel Wertheim of the University of California, San Diego, added: By re-running the introduction of SARS-CoV-2 into the US and Europe through simulations, we showed that it was very unlikely that the first documented viral introductions into these locales led to productive transmission clusters. Molecular epidemiological analyses are incredibly powerful for revealing transmissions patterns of SARS-CoV-2.”
“Our research shows that when you do early intervention and detection well, it can have a massive impact, both on preventing pandemics and controlling them once they progress,” Worobey said. “While the epidemic eventually slipped through, there were early victories that show us the way forward: Comprehensive testing and case identification are powerful weapons.”