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1.
JAMA Netw Open ; 4(11): e2132923, 2021 11 01.
Article in English | MEDLINE | ID: covidwho-1516695

ABSTRACT

Importance: Seroprevalence studies inform the extent of infection and assist evaluation of mitigation strategies for the COVID-19 pandemic. Objective: To estimate the prevalence of unidentified SARS-CoV-2 infection in the general population of Hong Kong. Design, Setting, and Participants: A prospective cross-sectional study was conducted in Hong Kong after each major wave of the COVID-19 pandemic (April 21 to July 7, 2020; September 29 to November 23, 2020; and January 15 to April 18, 2021). Adults (age ≥18 years) who had not been diagnosed with COVID-19 were recruited during each period, and their sociodemographic information, symptoms, travel, contact, quarantine, and COVID-19 testing history were collected. Main Outcomes and Measures: The main outcome was prevalence of SARS-CoV-2 infection. SARS-CoV-2 IgG antibodies were detected by an enzyme-linked immunosorbent assay based on spike (S1/S2) protein, followed by confirmation with a commercial electrochemiluminescence immunoassay based on the receptor binding domain of spike protein. Results: The study enrolled 4198 participants (2539 [60%] female; median age, 50 years [IQR, 25 years]), including 903 (22%), 1046 (25%), and 2249 (53%) during April 21 to July 7, 2020; during September 29 to November 23, 2020; and during January 15 to April 18, 2021, respectively. The numbers of participants aged 18 to 39 years, 40 to 59 years, and 60 years or older were 1328 (32%), 1645 (39%), and 1225 (29%), respectively. Among the participants, 2444 (58%) stayed in Hong Kong since November 2019 and 2094 (50%) had negative SARS-CoV-2 RNA test results. Only 170 (4%) reported ever having contact with individuals with confirmed cases, and 5% had been isolated or quarantined. Most (2803 [67%]) did not recall any illnesses, whereas 737 (18%), 212 (5%), and 385 (9%) had experienced respiratory symptoms, gastrointestinal symptoms, or both, respectively, before testing. Six participants were confirmed to be positive for anti-SARS-CoV-2 IgG; the adjusted prevalence of unidentified infection was 0.15% (95% CI, 0.06%-0.32%). Extrapolating these findings to the whole population, there were fewer than 1.9 unidentified infections for every recorded confirmed case. The overall prevalence of SARS-CoV-2 infection in Hong Kong before the roll out of vaccination was less than 0.45%. Conclusions and Relevance: In this cross-sectional study of participants from the general public in Hong Kong, the prevalence of unidentified SARS-CoV-2 infection was low after 3 major waves of the pandemic, suggesting the success of the pandemic mitigation by stringent isolation and quarantine policies even without complete city lockdown. More than 99.5% of the general population of Hong Kong remain naive to SARS-CoV-2, highlighting the urgent need to achieve high vaccine coverage.


Subject(s)
COVID-19 Testing , COVID-19/epidemiology , Pandemics , Population Health , SARS-CoV-2 , Adolescent , Adult , Aged , Aged, 80 and over , Antibodies, Viral/blood , COVID-19/diagnosis , COVID-19/virology , Communicable Disease Control , Cross-Sectional Studies , Female , Hong Kong , Humans , Immunoglobulin G/blood , Male , Middle Aged , Population Surveillance , Prevalence , Prospective Studies , RNA, Viral , SARS-CoV-2/genetics , SARS-CoV-2/immunology , Seroepidemiologic Studies , Young Adult
2.
Emerg Infect Dis ; 26(12): 3076-3078, 2020 12.
Article in English | MEDLINE | ID: covidwho-890312

ABSTRACT

In March 2020, mild signs and symptoms of coronavirus disease developed in a healthy 33-year-old man in Hong Kong. His first infection did not produce virus neutralizing antibodies. In August, he had asymptomatic reinfection, suggesting that persons without a robust neutralizing antibody response might be at risk for reinfection.


Subject(s)
COVID-19/immunology , Reinfection/diagnosis , Antibody Formation/immunology , Hong Kong , Humans , Male , Pandemics , SARS-CoV-2 , Young Adult
3.
Emerg Infect Dis ; 26(9)2020 Sep.
Article in English | MEDLINE | ID: covidwho-506041

ABSTRACT

We detected severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA on disposable wooden chopsticks used by 5 consecutive asymptomatic and postsymptomatic patients admitted for isolation and care at our hospital. Although we did not assess virus viability, our findings may suggest potential for transmission through shared eating utensils.


Subject(s)
Betacoronavirus/genetics , Cooking and Eating Utensils , Coronavirus Infections/virology , Fomites/virology , Pneumonia, Viral/virology , RNA, Viral/isolation & purification , COVID-19 , Coronavirus Infections/transmission , Hong Kong , Humans , Pandemics , Pneumonia, Viral/transmission , SARS-CoV-2 , Wood/virology
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