As the Covid-19 virus continues to spread unevenly across the world, politicians and opinion pages in the US are already blaming new cases of coronavirus on mass demonstrations against police violence and racism. The protests are a visible example of public crowds, and the ideal scapegoat for problems that are far more complex. Some leaders have treated them with overt hostility. But have protests really played a critical role in spreading new cases of coronavirus? The best science suggests probably not a lot.
Let me be clear: Iâ€™m not minimising the risk of mass demonstrations during a pandemic. Indeed, there is almost nothing we do at the moment that doesnâ€™t carry some risk of contagion, and it is undoubtedly true that they will lead to some new cases. But the big question is by how much, and whether there are ways to minimise this risk. Here, the answer is largely in favour of the outdoor protests over other large gatherings planned, such as indoor campaign rallies.
The evidence is becoming clear that wearing a mask can substantially lower the risk of spread and severity of illness. We are seeing more and more masks worn by protesters. A second feature of gatherings that affects the spread of the virus is whether they happen outdoors or indoors. Here, too, research suggests that outdoor activities are much safer than indoor ones.
Finally, although this is more preliminary, evidence suggests that if youâ€™re going to be in a crowd, a mobile one is better than a stationary one. None of these three aspects will protect you from infection definitively â€“ but together they offer a modest level of risk reduction. And compared with the risk of catching Covid-19 that is present in many jobs or other activities, such as working in meat-packing plants, outdoor protests are likely to be much saferâ€“ especially if we carry out testing, which can quickly reveal if the virus is spreading among protesters, as Massachusetts has done recently.