The updated fourth edition of Beijing's guide on home quarantining amid the COVID-19 pandemic was released on May 8, according to the website of the city's Center for Disease Prevention and Control. 

Detailing ventilation and sewage disposal requirements for homes, the guide states that people potentially exposed to the virus, both close and secondary contacts, must undergo centralized quarantine at designated places if community medical workers deem their residential conditions to be unsatisfactory.

Based on the city's latest quarantine measurements, a 10-day centralized quarantine and 7-day at-home quarantine are applied to close contacts. Secondary contacts should be quarantined at home for seven days, and risk-exposed groups should undergo a 10-day at-home quarantine plus 7-day health monitoring and required PCR and antigen tests, the city official said on May 4.

Compared to the previous version released in November 2021, the latest guide puts greater emphasis on ventilation and drainage systems in kitchens and bathrooms, stipulating that pipelines must be independent or separated from the residential building's shared drainage system through check valves.

Preventing virus spread via aerosols

Multiple studies have shown that SARS-CoV-2, the virus that causes COVID-19, spreads in the form of aerosols. 

Research published in the journal Nature on April 27 analyzed SARS-CoV-2 viral load in air and surface at the University of Michigan Ann Arbor campus from August 2020 until April 2021. 

It found that the estimated probability of infection was about 1 per 100 exposures to SARS-CoV-2-laden aerosols through inhalation as compared to 1 in every 100,000 exposures from contacting contaminated surfaces in simulated scenarios. 

A group of Chinese researchers also investigated a cluster infection case of COVID-19 in Beijing last November. Their result, published on the Chinese Journal of Epidemiology website on March 21, found that a family of five was infected during centralized quarantine at a hotel that was not properly ventilated and had drains connected through a shared pipe.

The updated guide has therefore made additional requirements for home quarantine and observation to minimize exposure to viral aerosols.