Clinical Chemistry | 2021
A Push for Real Normal: Mass Screening for COVID-19
Abstract
COVID-19 has been the worst pandemic in the last 100 years. The causative agent of this disease, SARSCoV-2, is highly transmissible in humans. As of August 20, 2021, SARS-CoV-2 has caused 210 million confirmed cases worldwide, resulting in 4.4 million deaths. Different governments have used different strategies to control this pandemic. Some have used a mitigation approach that aims at controlling the number of COVID-19 cases within a manageable number, whereas some have used a suppression approach that aims at reducing the number of COVID-19 cases to a minimum (1). Irrespective of which approach is used for controlling this pandemic, both approaches require comprehensive and accurate public health data to inform policy making or management. With the wide use of quantitative reverse transcription–PCR (RT–PCR) technology, it is now possible to provide accurate and timely laboratory diagnostic test results to public health experts and other stakeholders in a robust manner. This is in sharp contrast to the last influenza pandemic in 2009, in which the diagnosis in many clinical settings was mainly based on clinical observations (2), resulting in an underestimation of actual number of deaths caused by the pandemic influenza A (H1N1) 2009 virus. Hong Kong thus far has adopted an elimination strategy to suppress COVID-19 circulation in the city (3). With a population of 7.5 million, Hong Kong so far has only 12 033 confirmed COVID-19 cases and about 21% of these patients were imported cases. The number of daily COVID-19 cases in the city has been reduced to a single digit level or 0 since late March 2021. Hong Kong has taken strict nonpharmaceutical measures (e.g., ban on mass gathering, mandatory mask wearing in public places, and closure of schools) to prevent major COVID-19 outbreaks in the city (4). Active contact tracing is performed for all confirmed COVID19 cases if possible (5). Individuals in close contact with COVID-19 patients have to be subjected to a mandatory quarantine. Stringent travel restrictions have been imposed. All inbound passengers, irrespective of their vaccination status, must be quarantined. Among these nonpharmaceutical measures, Hong Kong has heavily used nucleic acid amplification tests (NAATs) to control and monitor COVID-19. In addition to routine COVID-19 diagnosis, NAATs have been used extensively in various COVID-19 surveillance programs in Hong Kong. Mandatory COVID-19 RT– PCR testing before and after an inbound flight is requested for all inbound passengers. Individuals who are classified as high-risk cases in COVID-19 outbreak investigations have to be RT–PCR tested for SARSCoV-2 repeatedly. Free NAATs are offered to all Hong Kong citizens who feel they have a higher risk of exposure or are experiencing clinical symptoms of respiratory infections. In addition, NAATs are used in different large-scale community COVID-19 screening programs. To prevent SARS-CoV-2 transmissions caused by asymptomatic patients in the community, NAATs have also been used in a citywide sewage surveillance program in Hong Kong. In this program, wastewater samples collected from different districts or individual buildings are RT–PCR tested for SARS-CoV-2 (6). Occupants from the so-called “COVID-19 positive buildings” are shortly subjected to mandatory COVID-19 NAATs. At the end of Wave 4 of COVID-19 in Hong Kong (April 2021), this sewage surveillance program identified >110 COVID-19 positive buildings and >50 previously unknown patients with COVID-19 in these buildings. In addition, to better understand the transmission dynamics of SARS-CoV-2 in the city, Hong Kong has conducted real-time molecular epidemiology of SARS-CoV-2 and studied about 20% of COVID-19 patients. Such analyses have provided information to relevant stakeholders for developing evidence-based COVID-19 control policy. In short, Hong Kong exemplifies the potential use of NAATs for controlling infectious diseases. There are ample opportunities to apply NAATs for robust disease surveillance, thereby providing timely results to inform public health policy making and practice. Although guidelines for COVID-19 specific NAATs (7, 8) were released by the World Health Organization soon after the discovery of SARS-CoV-2, the potential use of NAATs for controlling COVID-19 has been severely affected by several practical hurdles at the beginning of this pandemic. In particular, with the “unexpected” huge surge in demand for testing, it was School of Public Health, The University of Hong Kong, Hong Kong, China; HKU-Pasteur Research Pole, LKS Faculty of Medicine, The University of Hong Kong, China; Centre for Immunology & Infection, Hong Kong Science Park, Hong Kong, China *Address correspondence to this author at: School of Public Health, The University of Hong Kong, Sassoon Road, Hong Kong. Fax: þ852 28551241; E-mail: llmpoon@hku. hk. Received August 21, 2021; accepted August 24, 2021. DOI: 10.1093/clinchem/hvab190