Institutional versus home isolation to curb the COVID-19 outbreak - Authors' reply.

We thank Ajeet Singh Bhadoria and colleagues for their insightful comments in response to our Correspondence. Although we focus on teasing out the impact of institutional isolation beyond the other non-pharmaceutical measures, we agree that isolation of all cases cannot be a stand-alone strategy. The pandemic response to COVID-19 must be a multipronged approach that includes liberal testing, tracing and quarantine of contacts, physical distancing, and widespread use of face masks—such a multipronged approach is particularly crucial for a disease with a high asymptomatic rate. However, we disagree with Bhadoria and colleagues on several other points.

The authors offer two examples of countries with successful mitigation without case isolation, but recent data from the evolving epidemic show that neither Israel nor Germany have truly mitigated the outbreak. As of Sept 18, 2020, Israel became the first country to announce a second country-wide lockdown. Germany has been a role model in Europe based on extensive testing, tracing, and quarantine of contacts, but it did not contain the outbreak to the extent that various Asian countries did. We invite Bhadoria and colleagues to look further east, to China, Taiwan, South Korea, and Vietnam, for templates for success in preventing or mitigating widespread community spread. These countries employed isolation of all cases, even mild ones, often using isolation shelters, hospitals, or other institutions such as hotels.3, 4

Careful study of the sequential mounting of public health responses in Wuhan, China, to combat their explosive outbreak in January and February, 2020, showed five distinct phases. Only in the fourth and fifth phases, when isolation shelters for all cases (even mild cases) were instituted, did the epidemic curve not only flatten but show a rapid decline in daily new cases, down to zero within a matter of weeks. Of note, these shelters for isolation of mild cases were facilities built as make-shift hospitals in addition to existing health-care facilities.

Why is institutional isolation such an impactful additional tool in the public health armamentarium to combat a respiratory pathogen associated with droplet, contact, and possibly even aerosol transmission? Because voluntary self-isolation of mild cases at home will always lead to some degree of non-compliance, thus further propagating transmission within households and into the community. As viral loads are high even in mild cases, mild cases can efficiently transmit the virus. There are ample reports that secondary attack rates in household settings are higher than in most other settings. In fact, 46–66% of transmission is household-based (using the standard formula for attributable fraction). We need to zoom in our efforts on those settings where transmission is high.

The advantages of isolation of infected individuals in designated facilities are manifold. First, moving infected people out of their households and communities will interrupt chains of onward transmission. Second, even make-shift isolation shelters can provide medical monitoring to identify those patients who might clinically deteriorate, which usually happens around day 7–12 of illness. About 11% of mild cases deteriorate, often rapidly, with hypoxaemic pneumonia; hence mechanisms for rapid referrals from low-care isolation shelters to hospitals with higher levels of medical care will enhance clinical prognosis. Third, many self-isolating patients report loneliness and lack of access to daily necessities such as food. Isolation shelters can provide food, social activities, and company. Finally, isolation of all cases, even mild ones, will benefit the society at large as containing outbreaks early will prevent damaging lockdowns. It will also allow for speedier recovery of the economy as now seen in China.

Despite these advantages, we agree with Bhadoria and colleagues that there are several challenges with facility-based isolation of mild COVID-19. Make-shift hospitals or shelters where hundreds of infected people are cohorted might not be culturally acceptable in many societies—though such facilities have a long history—and cannot be legally enforceable in some jurisdictions. There are, however, other potentially more palatable options to isolate COVID-19 patients. Hotels or dormitories could be re-purposed, for example. Given the high global incidence of mild COVID-19 cases, we might not be able to rapidly scale up such facilities for all of those with mild disease. Those who live in multi-generational families, those staying at home with individuals at risk of severe COVID-19 outcomes, and those who live in single households and might benefit from company and provision of food should be prioritised.

Appropriate communication and awareness need to be enhanced for better community acceptance of facility-based isolation. If populations are made aware of the public health benefit of institutional isolation, appreciate the fact that such isolation will lead to better protection of their loved ones, and is associated with better clinical care for themselves, including easy access to food and practical support, maybe public acceptance will increase.