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Infectious Diseases

Updated 04 June 2020

Covid-19: For every day delay in distancing, the length of the outbreak is significantly longer

New research suggests that for every day delayed after emergence of the first Covid-19 case, a period of 2.4 days could be added to the length of the outbreak.

  • Many areas around the world implemented Covid-19 physical distancing measures
  • Areas that delayed doing so could have to deal longer with an outbreak 
  • The earlier physical distancing measures are implemented, the better


A new analysis of the Covid-19 outbreak in 58 cities shows that places that took longer to start implementing measures of physical distancing allowed more time for the virus to spread rapidly, leading to a longer outbreak than in those areas who started measures earlier, according to a news release.

The study by a team of epidemiological researchers at the University of Texas in Austin is now in press at the CDC’s journal Emerging Infectious Diseases.

Every day delay made outbreak longer

In the new research, the team studied cities throughout China when the first cases emerged, when physical distancing measures were implemented and when the outbreak was under control.

The research suggested that for every day delayed after the first case emerged, a period of 2.4 days could be added to the length of the outbreak.

"Every day saves time, saves effort, saves people becoming infected and probably saves lives," stated Lauren Ancel Meyers, a professor of integrative biology in the press release. “This is particularly important as we think about the coming weeks and months."

How do scientists know when an outbreak is “contained”?

For an outbreak in a specific area to be considered under control, scientists take a look at case counts and the so-called “reproduction number” or R-naught. This number shows how many people will be infected by one positive case. The R-naught should be below one for scientists to consider the outbreak contained.

Which physical distances are most effective?

This study did not determine which measures were the most effective in containing the spread of Covid-19, but according to the research, the timing of the first measure made a significant difference to the spread, and obtaining the necessary R-naught to consider the outbreak contained.

"We provide direct, data-driven evidence that the timing of interventions has a substantial impact on how long an outbreak lasts, how effective our interventions are and, ultimately, how many people might be infected and die from the virus," Meyers stated.

And even though the data looked at cities during the first days of the Covid-19 outbreak, the research is relevant for those cities still in the midst of an outbreak, Meyers said.

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