Due to the COVID-19 pandemic, a number of non-pharmaceutical interventions colloquially known as lockdowns (encompassing stay-at-home orders, curfews, quarantines, cordons sanitaires and similar societal restrictions) have been implemented in numerous countries and territories around the world. These restrictions were established to reduce the spread of SARS-CoV-2, the virus that causes COVID-19. By April 2020, about half of the world's population was under some form of lockdown, with more than 3.9 billion people in more than 90 countries or territories having been asked or ordered to stay at home by their governments. Although similar disease control measures have been used for hundreds of years, the scale seen in the 2020s is thought to be unprecedented.Research and case studies have shown that lockdowns are effective at reducing the spread of COVID-19, therefore flattening the curve. The World Health Organization's recommendation on curfews and lockdowns is that they should be short-term measures to reorganize, regroup, rebalance resources, and protect health workers who are exhausted. To achieve a balance between restrictions and normal life, the WHO recommends a response to the pandemic that consists of strict personal hygiene, effective contact tracing, and isolating when ill.Although public health experts and economists generally supported lockdown restrictions, citing greater long-term costs for allowing the disease to spread uncontrollably, pandemic restrictions have had health, social, and economic impacts, and have been met with protests in some territories.