How lockdown halts the spread of Covid19

Many countries are currently in some degree of “lockdown,” with restaurants and bars, shops, schools and gyms closed, and citizens required, or at least strongly encouraged, to stay home to avoid catching or spreading COVID-19, the respiratory illness caused by the novel coronavirus.

Researchers are well on their way to discovering vaccines and treatments for the virus, but even in a best-case scenario, these are likely to be 12-18 months away.

Until then, extreme social distancing is pretty much the only intervention available to help individuals stay healthy, and to break the chain of transmission - giving more vulnerable populations a fighting chance of surviving this pandemic. But how exactly does a lockdown work? And why is it important for even younger and healthier people, who face a lower risk of severe illness, to remain in their homes as much as possible?

The purpose of a lockdown, explains a new study from the Imperial College London COVID-19 Response Team, is to reduce reproduction – in other words, to reduce the number of people each confirmed case infects. The goal is to keep reproduction, or “R,” below one (R<1) – with each case infecting fewer than one other person, on average. The authors of the study say there are two routes to try to get there: Mitigation, “slowing but not necessarily stopping epidemic spread – reducing peak healthcare demand while protecting those most at risk of severe disease from infection.” This is done by isolating suspected cases and their households, and social distancing the elderly and people at highest risk of serious illness.

Suppression, or basically, lockdown, which “aims to reverse epidemic growth, reducing case numbers to low levels” by social distancing the entire population “indefinitely” and closing schools and universities. The study’s models show that, painful as lockdown may be for many of us, it works. Without any lockdown or social distancing measures, we can expect peak mortality in approximately three months. In this scenario, 81% of the UK and US populations would be infected, with 510,000 dying in the UK and 2.2 million dying in the US.

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