COVID-19 spreads via aerosols, droplets, fomites and faeces. The built environment that facilitates crowding increases exposure and hence transmission of COVID-19 as evidenced by outbreaks in both cool-dry and hot-humid climates, such as in the US prison system and dormitories in Singapore, respectively. This paper explores how the built environment influences crowding and COVID-19 transmission, focusing on informal urban settlements (slums). We propose policy and practice changes that could reduce COVID-19 transmission. There are several issues on how COVID-19 affects informal urban settlements. Slum populations tend to be younger than the overall population. Lower numbers of older people lessen the morbidity and mortality of the pandemic in slum areas. Second, many slum populations are highly mobile. By returning to their ancestral villages residents can avoid the risks of overcrowding and reduce the population density in a given area but may spread COVID-19 to other areas. Third, detection and registration of COVID-19 cases depends on patients presenting to health care providers. If the risk of visiting a health care centre outweighs the potential benefits patients may prefer not to seek treatment. The control and prevention of COVID-19 in informal urban settlements starts with organizing community infrastructure for diagnosis and treatment and assuring that basic needs (food, water, sanitation, health care and public transport) are met during quarantine. Next, community members at highest risk need to be identified and protected. Low-income, informal settlements need to be recognized as a reservoir and source for persistent transmission. Solutions to overcrowding must be developed for this and future pandemics. In view of the constant risk that slums present to the entire population decisive steps need to be taken to rehabilitate and improve informal settlements, while avoiding stigmatization.

中文翻译：

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拥挤会产生后果：非正式城市住区 COVID-19 的预防和管理

COVID-19 通过气溶胶、飞沫、污染物和粪便传播。促进拥挤的建筑环境增加了暴露，从而增加了 COVID-19 的传播，这在凉爽干燥和炎热潮湿的气候中爆发就证明了这一点，例如分别在美国监狱系统和新加坡的宿舍中。本文探讨了建筑环境如何影响拥挤和 COVID-19 传播，重点关注非正规城市住区（贫民窟）。我们提出可以减少 COVID-19 传播的政策和实践变化。关于 COVID-19 如何影响非正规城市住区存在几个问题。贫民窟人口往往比总人口更年轻。较少的老年人减少了贫民区流行病的发病率和死亡率。其次，许多贫民窟人口流动性很强。通过返回他们祖传的村庄，居民可以避免过度拥挤的风险并降低特定地区的人口密度，但可能会将 COVID-19 传播到其他地区。第三，COVID-19 病例的检测和登记取决于向医疗保健提供者就诊的患者。如果去医疗保健中心的风险大于潜在的好处，患者可能不愿意寻求治疗。在非正规城市住区控制和预防 COVID-19 始于组织用于诊断和治疗的社区基础设施，并确保在检疫期间满足基本需求（食物、水、卫生、医疗保健和公共交通）。接下来，需要识别和保护风险最高的社区成员。需要将低收入、非正式住区视为持续传播的蓄水池和源头。必须为这次和未来的流行病制定过度拥挤的解决方案。鉴于贫民窟给全体居民带来的持续风险，需要采取果断措施来修复和改善非正规住区，同时避免污名化。