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1.
Clin Infect Dis ; 2021 Oct 28.
Article in English | MEDLINE | ID: covidwho-2017775

ABSTRACT

BACKGROUND: Testing of an entire community has been used as an approach to control COVID-19. In Hong Kong, a universal community testing programme (UCTP) was implemented at the fadeout phase of a community epidemic in July to September 2020. We described the utility of the UCTP in finding unrecognised infections, and analysed data from the UCTP and other sources to characterise transmission dynamics. METHODS: We described the characteristics of people participating in the UCTP and compared the clinical and epidemiological characteristics of COVID-19 cases detected by the UCTP versus those detected by clinical diagnosis and public health surveillance (CDPHS). We developed a Bayesian model to estimate the age-specific incidence of infection and the proportion of cases detected by CDPHS. RESULTS: 1.77 million people, 24% of the Hong Kong population, participated in the UCTP from 1 to 14 September 2020. The UCTP identified 32 new infections (1.8 per 100,000 samples tested), consisting of 29% of all local cases reported during the two-week UCTP period. Compared with the CDPHS, the UCTP detected a higher proportion of sporadic cases (62% versus 27%, p <0.01) and identified 6 (out of 18) additional clusters during that period. We estimated that 27% (95% credible interval: 22%, 34%) of all infections were detected by the CDPHS in the third wave. CONCLUSIONS: We reported empirical evidence of the utility of population-wide COVID-19 testing in detecting unrecognised infections and clusters. Around three quarters of infections have not been identified through existing surveillance approaches including contact tracing.

2.
The Lancet Infectious Diseases ; 2022.
Article in English | ScienceDirect | ID: covidwho-1996735

ABSTRACT

Summary Background Data on the effectiveness of oral antivirals in patients with mild-to-moderate COVID-19 are urgently needed. This retrospective cohort study aimed to evaluate the clinical and virological outcomes associated with molnupiravir or nirmatrelvir–ritonavir use in hospitalised patients with mild-to-moderate COVID-19 during a pandemic wave dominated by the omicron BA.2 subvariant. Methods We analysed data from a territory-wide retrospective cohort of patients in Hong Kong who were hospitalised with a confirmed diagnosis of SARS-CoV-2 infection between Feb 26 and April 26, 2022. Data were extracted from the Hospital Authority, the Department of Health, and the Hong Kong Death Registry. Patients were eligible for inclusion if their admission date was within 3 days before or after confirmation of their COVID-19 diagnosis. Those who were admitted to hospital more than 5 days after symptom onset, were younger than 18 years, had a history of oral antiviral use before admission, required supplemental oxygen on admission, had drug-related contraindications to nirmatrelvir–ritonavir use, or had severe renal or severe liver impairment were excluded. Patients who received the oral antivirals molnupiravir or nirmatrelvir–ritonavir were matched with controls using propensity-score matching in a ratio of 1:1. The primary outcome was all-cause mortality and secondary outcomes included a composite outcome of disease progression (all-cause mortality, initiation of invasive mechanical ventilation [IMV], intensive care unit [ICU] admission, or the need for oxygen therapy) and each of these individual disease progression outcomes, and time to reaching a low viral burden (RT-PCR cycle threshold value ≥30). For each event outcome, crude incidence rates were calculated and hazard ratios (HRs) estimated using Cox regression models. Findings We identified 40 776 patients hospitalised with SARS-CoV-2 infection during the study period, with a mean follow-up of 41·3 days (total 925 713 person-days). After exclusions and propensity-score matching, we included 1856 molnupiravir recipients and 1856 matched controls, and 890 nirmatrelvir-ritonavir recipients and 890 matched controls. A lower risk of all-cause mortality was observed in molnupiravir recipients (crude incidence rate per 10 000 person-days 19·98 events [95% CI 16·91–23·45]) versus matched controls (38·07 events [33·85–42·67];HR 0·48 [95% CI 0·40–0·59], p<0·0001) and in nirmatrelvir–ritonavir recipients (10·28 events [7·03–14·51]) versus matched controls (26·47 events [21·34–32·46];HR 0·34 [0·23–0·50], p<0·0001). Oral antiviral recipients also had lower risks of the composite disease progression outcome (molnupiravir HR 0·60 [95% CI 0·52–0·69], p<0·0001;nirmatrelvir–ritonavir 0·57 [0·45–0·72], p<0·0001) and need for oxygen therapy (molnupiravir 0·69 [0·57–0·83], p=0·0001;nirmatrelvir–ritonavir 0·73 [0·54–0·97], p=0·032) compared with controls. Time to achieving a low viral burden was significantly shorter among oral antiviral recipients than matched controls (molnupiravir HR 1·38 [95% CI 1·15–1·64], p=0·0005;nirmatrelvir–ritonavir 1·38 [1·07–1·79], p=0·013). Significant differences in initiation of IMV and ICU admission were not found. Interpretation During a wave of SARS-CoV-2 omicron BA.2, initiation of novel oral antiviral treatments in hospitalised patients not requiring oxygen therapy on admission showed substantial clinical benefit. Our findings support the early use of oral antivirals in this population of patients. Funding Health and Medical Research Fund (Health Bureau, Government of the Hong Kong Special Administrative Region). Translation For the Chinese translation of the see Supplementary Materials section.

3.
Emerg Infect Dis ; 28(9)2022 Aug 01.
Article in English | MEDLINE | ID: covidwho-1974605

ABSTRACT

Our analysis of data collected from multiple epidemics in Hong Kong indicated a shorter serial interval and generation time of infections with the SARS-CoV-2 Omicron variant. The age-specific case-fatality risk for Omicron BA.2.2 case-patients without complete primary vaccination was comparable to that of persons infected with ancestral strains in earlier waves.

4.
Lancet Infect Dis ; 2022 Jul 15.
Article in English | MEDLINE | ID: covidwho-1937333

ABSTRACT

BACKGROUND: Hong Kong maintained low circulation of SARS-CoV-2 until a major community epidemic of the omicron (B.1.1.529) sublineage BA.2 began in January 2022. Both mRNA (BNT162b2 [Fosun Pharma-BioNTech]) and inactivated CoronaVac (Sinovac, Beijing, China) vaccines are widely available; however, vaccination coverage has been low, particularly in older adults aged 70 years or older. We aimed to assess vaccine effectiveness in this predominantly infection-naive population. METHODS: In this observational study, we used individual-level case data on mild or moderate, severe or fatal, and fatal disease in patients hospitalised with COVID-19 along with census information and coverage data of BNT162b2 and CoronaVac. We used a negative binomial model, adjusting for age, sex, and calendar day to estimate vaccine effectiveness of one, two, and three doses of both BNT162b2 and CoronaVac vaccines, and relative effectiveness by number of doses and vaccine type. FINDINGS: Between Dec 31, 2021, and March 16, 2022, 13·2 million vaccine doses were administered in Hong Kong's 7·4-million population. We analysed data from confirmed cases with mild or moderate (n=5566), severe or fatal (n=8875), and fatal (n=6866) COVID-19. Two doses of either vaccine protected against severe disease and death within 28 days of a positive test, with higher effectiveness among adults aged 60 years or older with BNT162b2 (vaccine effectiveness 89·3% [95% CI 86·6-91·6]) compared with CoronaVac (69·9% [64·4-74·6]). Three doses of either vaccine offered very high levels of protection against severe or fatal outcomes (97·9% [97·3-98·4]). INTERPRETATION: Third doses of either BNT162b2 or CoronaVac provide substantial additional protection against severe COVID-19 and should be prioritised, particularly in older adults older than 60 years and others in high-risk populations who received CoronaVac primary schedules. Longer follow-up is needed to assess duration of protection across different vaccine platforms and schedules. FUNDING: COVID-19 Vaccines Evaluation Program, Chinese Center for Disease Control and Prevention.

5.
PLoS Med ; 19(7): e1003939, 2022 07.
Article in English | MEDLINE | ID: covidwho-1933196

ABSTRACT

Kenji Shibuya and coauthors discuss the potential contribution of East Asian countries to global health in the light of COVID-19.


Subject(s)
COVID-19 , COVID-19/epidemiology , Far East/epidemiology , Global Health , Humans
6.
Clin Infect Dis ; 2022 Jun 08.
Article in English | MEDLINE | ID: covidwho-1890904

ABSTRACT

BACKGROUND: Limited data exist on antibody responses to mixed vaccination strategies involving inactivated COVID-19 vaccines, particularly in the context of emerging variants. METHODS: We conducted an open label trial of a third vaccine dose of an mRNA vaccine (BNT162b2, Fosun Pharma/BioNTech) in adults aged ≥30 years who had previously received two doses of inactivated COVID-19 vaccine. We collected blood samples before administering the third dose and 28 days later, and tested for antibodies to the ancestral virus using a binding assay (ELISA), a surrogate virus neutralization test (sVNT) and a live virus plaque reduction neutralization test (PRNT). We also tested for antibodies against the Omicron variant using live-virus PRNT. RESULTS: In 315 participants, a third dose of BNT162b2 substantially increased antibody titers on each assay. Mean ELISA levels increased from an optical density (OD) of 0.3 to 2.2 (p < 0. 001), and mean sVNT levels increased from an inhibition of 17% to 96% (p < 0.001). In a random subset of 20 participants, the geometric mean PRNT50 titers rose very substantially by 45 fold from Day 0 to Day 28 against the ancestral virus (p < 0.001) and rose by 11 fold against the Omicron variant (p < 0.001). In daily monitoring, post-vaccination reactions subsided within 7 days for over 99% of participants. CONCLUSIONS: A third dose of COVID-19 vaccination with an mRNA vaccine substantially improved antibody levels against the ancestral virus and the Omicron variant with well-tolerated safety profile, in adults who had received two doses of inactivated vaccine 6 months earlier.

7.
Vaccine ; 40(32): 4312-4317, 2022 Jul 30.
Article in English | MEDLINE | ID: covidwho-1886118

ABSTRACT

We studied 2780 adults in Hong Kong who received CoronaVac inactivated virus vaccine (Sinovac) and BNT162b2 mRNA vaccine ("Comirnaty", BioNTech/Fosun Pharma). We compared rates of antibody waning over time using an enzyme-linked immunosorbent assay for spike receptor binding domain and a surrogate virus neutralization test. We found stronger and more durable antibody responses to two doses of the mRNA vaccine, and slightly stronger initial antibody responses to each vaccine in younger adults and women. The weaker and less durable responses following CoronaVac support earlier provision of third doses to persons who previously received two doses of this vaccine.


Subject(s)
Antibody Formation , BNT162 Vaccine , Adult , Antibodies, Viral , COVID-19 Vaccines , Female , Humans , Vaccines, Synthetic , mRNA Vaccines
9.
Environ Sci Technol ; 2022 May 18.
Article in English | MEDLINE | ID: covidwho-1852362

ABSTRACT

Sewage surveillance is increasingly employed as a supplementary tool for COVID-19 control. Experiences learnt from large-scale trials could guide better interpretation of the sewage data for public health interventions. Here, we compared the performance of seven commonly used primer-probe sets in RT-qPCR and evaluated the usefulness in the sewage surveillance program in Hong Kong. All selected primer-probe sets reliably detected SARS-CoV-2 in pure water at 7 copies per µL. Sewage matrix did not influence RT-qPCR determination of SARS-CoV-2 concentrated from a small-volume sewage (30 mL) but introduced inhibitory impacts on a large-volume sewage (920 mL) with a ΔCt of 0.2-10.8. Diagnostic performance evaluation in finding COVID-19 cases showed that N1 was the best single primer-probe set, while the ORF1ab set is not recommended. Sewage surveillance using the N1 set for over 3200 samples effectively caught the outbreak trend and, importantly, had a 56% sensitivity and a 96% specificity in uncovering the signal sources from new cases and/or convalescent patients in the community. Our study paves the way for selecting detection primer-probe sets in wider applications in responding to the COVID-19 pandemic.

10.
Environ Health Perspect ; 130(5): 57008, 2022 May.
Article in English | MEDLINE | ID: covidwho-1846899

ABSTRACT

BACKGROUND: Sewage surveillance, by detecting SARS-CoV-2 virus circulation at the community level, has the potential to supplement individual surveillance for COVID-19. However, to date, there have been no reports about the large-scale implementation and validation of sewage surveillance for public health action. OBJECTIVE: Here, we developed a standardized approach for SARS-CoV-2 detection in sewage and applied it prospectively to supplement public health interventions. METHODS: We analyzed 1,169 sewage samples collected at 492 sites from December 2020 to March 2021. Forty-seven of 492 sites tested positive, 44 (94%) of them had traceable sources of viral signals in the corresponding sewershed, either from previously unsuspected but subsequently confirmed patients or recently convalescent patients or from both patient groups. RESULTS: Sewage surveillance had a sensitivity of 54%, a specificity of 95%, a positive predictive value of 53%, and a negative predictive value of 95% for identifying a previously unsuspected patient within a sewershed. Sewage surveillance in Hong Kong provided a basis for the statutory public health action to detect silent COVID-19 transmission. DISCUSSION: Considering the epidemiological data together with the sewage testing results, compulsory testing was conducted for individual residents at 27 positive sewage sites and uncovered total of 62 previously unsuspected patients, demonstrating the value of sewage surveillance in uncovering previously unsuspected patients in the community. Our study suggests that sewage surveillance could be a powerful management tool for the control of COVID-19. https://doi.org/10.1289/EHP9966.


Subject(s)
COVID-19 , COVID-19/epidemiology , Hong Kong/epidemiology , Humans , Public Health , SARS-CoV-2 , Sewage
11.
MMWR Morb Mortal Wkly Rep ; 71(15): 545-548, 2022 Apr 15.
Article in English | MEDLINE | ID: covidwho-1789731

ABSTRACT

On January 6, 2022, a cluster of COVID-19 cases* caused by the Omicron variant of SARS-CoV-2, the virus that causes COVID-19, was detected in Hong Kong Special Administrative Region, China (Hong Kong), resulting in the territory's fifth wave of COVID-19 cases (1). This wave peaked on March 4, 2022, with 8,764 COVID-19 cases per million population (2), resulting in a total of 1,049,959 cases and 5,906 COVID-19-associated deaths reported to the Hong Kong Department of Health during January 6-March 21, 2022.† Throughout this period, the COVID-19 mortality rate in Hong Kong (37.7 per million population) was among the highest reported worldwide since the COVID-19 pandemic began (3). Publicly available data on age-specific vaccination coverage in Hong Kong with a 2-dose primary vaccination series (with either Sinovac-CoronaVac [Sinovac], an inactivated COVID-19 viral vaccine, recommended for persons aged ≥3 years or BNT162b2 [Pfizer-BioNTech], an mRNA vaccine, for persons aged ≥5 years), as of December 23, 2021,§,¶ and COVID-19 mortality during January 6-March 21, 2022, were analyzed. By December 23, 2021, 67% of vaccine-eligible persons in Hong Kong had received ≥1 dose of a COVID-19 vaccine, 64% had received ≥2 doses, and 5% had received a booster dose. Among persons aged ≥60 years, these proportions were 52%, 49%, and 7%, respectively. Among those aged ≥60 years, vaccination coverage declined with age: 48% of persons aged 70-79 years had received ≥1 dose, 45% received ≥2 doses, and 7% had received a booster, and among those aged ≥80 years, 20%, 18%, and 2% had received ≥1 dose, ≥2 doses, and a booster dose, respectively. Among 5,906 COVID-19 deaths reported, 5,655 (96%) occurred in persons aged ≥60 years**; among these decedents, 3,970 (70%) were unvaccinated, 18% (1,023) had received 1 vaccine dose, and 12% (662) had received ≥2 doses. The overall rates of COVID-19-associated mortality among persons aged ≥60 years who were unvaccinated, who had received 1 COVID-19 vaccine dose, and who had received ≥2 vaccine doses were 10,076, 1,099, and 473 per million population, respectively; the risk for COVID-19-associated death among unvaccinated persons was 21.3 times that among recipients of 2-3 doses in this age group. The high overall mortality rate during the ongoing 2022 Hong Kong Omicron COVID-19 outbreak is being driven by deaths among unvaccinated persons aged ≥60 years. Efforts to identify and address gaps in age-specific vaccination coverage can help prevent high mortality from COVID-19, especially among persons aged ≥60 years.


Subject(s)
COVID-19 , Aged , BNT162 Vaccine , COVID-19/prevention & control , COVID-19 Vaccines , Child, Preschool , China , Hong Kong/epidemiology , Humans , Pandemics , SARS-CoV-2 , Vaccines, Synthetic , mRNA Vaccines
12.
China CDC Wkly ; 4(14): 288-292, 2022 Apr 08.
Article in English | MEDLINE | ID: covidwho-1786623

ABSTRACT

What is already known about this topic?: COVID-19 vaccines are important tools to protect populations from severe disease and death. What is added by this report?: Among persons aged ≥60 years in Hong Kong, 49%, had received ≥2 doses of a COVID-19 vaccine, and vaccination coverage declined with age. During January-March 2022, reported COVID-19-associated deaths rose rapidly in Hong Kong. Among these deaths, 96% occurred in persons aged ≥60 years; within this age group, the risk for death was 20 times lower among those who were fully vaccinated compared with those who were unvaccinated. What are the implications for public health practice?: Efforts to identify and address gaps in age-specific vaccination coverage can help prevent high mortality from COVID-19, especially in older adults.

13.
Front Public Health ; 9: 726617, 2021.
Article in English | MEDLINE | ID: covidwho-1775848

ABSTRACT

The associations between absolute vs. relative income at the household or neighborhood level and cardiovascular disease (CVD) risk remain understudied in the Chinese context. Further, it is unclear whether stress biomarkers, such as cortisol, are on the pathway from income to CVD risk. We examined the associations of absolute and relative income with CVD risk observationally, as well as the mediating role of cortisol, and validated the role of cortisol using Mendelian Randomization (MR) in Hong Kong Chinese. Within Hong Kong's FAMILY Cohort, associations of absolute and relative income at both the individual and neighborhood levels with CVD risk [body mass index (BMI), body fat percentage, systolic blood pressure, diastolic blood pressure, self-reported CVD and self-reported diabetes] were examined using multilevel logistic or linear models (n = 17,607), the mediating role of cortisol using the mediation analysis (n = 1,562), and associations of genetically predicted cortisol with CVD risk using the multiplicative generalized method of moments (MGMMs) or two-stage least squares regression (n = 1,562). In our cross-sectional observational analysis, relative household income deprivation (per 1 SD, equivalent to USD 128 difference in Yitzhaki index) was associated with higher systolic blood pressure (0.47 mmHg, 95% CI 0.30-0.64), but lower BMI (-0.07 kg/m2, 95% CI -0.11 to -0.04), independent of absolute income. Neighborhood income inequality was generally unrelated to CVD and its risk factors, nor was absolute income at the household or neighborhood level. Cortisol did not clearly mediate the association of relative household income deprivation with systolic blood pressure. Using MR, cortisol was unrelated to CVD risk. Based on our findings, relative household income deprivation was not consistently associated with cardiovascular health in Hong Kong Chinese, nor were neighborhood income inequality and absolute income, highlighting the context-specific ways in which relative and absolute income are linked to CVD risk.


Subject(s)
Mendelian Randomization Analysis , Cross-Sectional Studies , Hong Kong/epidemiology , Humans , Income , Mendelian Randomization Analysis/methods
14.
Epidemics ; 38: 100552, 2022 03.
Article in English | MEDLINE | ID: covidwho-1757327

ABSTRACT

COVID-19 disease models have aided policymakers in low-and middle-income countries (LMICs) with many critical decisions. Many challenges remain surrounding their use, from inappropriate model selection and adoption, inadequate and untimely reporting of evidence, to the lack of iterative stakeholder engagement in policy formulation and deliberation. These issues can contribute to the misuse of models and hinder effective policy implementation. Without guidance on how to address such challenges, the true potential of such models may not be realised. The COVID-19 Multi-Model Comparison Collaboration (CMCC) was formed to address this gap. CMCC is a global collaboration between decision-makers from LMICs, modellers and researchers, and development partners. To understand the limitations of existing COVID-19 disease models (primarily from high income countries) and how they could be adequately support decision-making in LMICs, a desk review of modelling experience during the COVID-19 and past disease outbreaks, two online surveys, and regular online consultations were held among the collaborators. Three key recommendations from CMCC include: A 'fitness-for-purpose' flowchart, a tool that concurrently walks policymakers (or their advisors) and modellers through a model selection and development process. The flowchart is organised around the following: policy aims, modelling feasibility, model implementation, model reporting commitment. Holmdahl and Buckee (2020) A 'reporting standards trajectory', which includes three gradually increasing standard of reports, 'minimum', 'acceptable', and 'ideal', and seeks collaboration from funders, modellers, and decision-makers to enhance the quality of reports over time and accountability of researchers. Malla et al. (2018) A framework for "collaborative modelling for effective policy implementation and evaluation" which extends the definition of stakeholders to funders, ground-level implementers, public, and other researchers, and outlines how each can contribute to modelling. We advocate for standardisation of modelling processes and adoption of country-owned model through iterative stakeholder participation and discuss how they can enhance trust, accountability, and public ownership to decisions.


Subject(s)
COVID-19 , Health Policy , COVID-19/epidemiology , Humans , Pandemics , Policy Making
15.
Emerg Infect Dis ; 28(2): 467-470, 2022 02.
Article in English | MEDLINE | ID: covidwho-1736706

ABSTRACT

We report surveillance conducted in 217 pestiferous rodents in Hong Kong for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We did not detect SARS-CoV-2 RNA but identified 1 seropositive rodent, suggesting exposure to a virus antigenically similar to SARS-CoV-2. Potential exposure of urban rodents to SARS-CoV-2 cannot be ruled out.


Subject(s)
COVID-19 , SARS-CoV-2 , Animals , Hong Kong/epidemiology , Humans , RNA, Viral/genetics , Rodentia
16.
Lancet ; 399(10329): 1070-1078, 2022 03 12.
Article in English | MEDLINE | ID: covidwho-1735071

ABSTRACT

BACKGROUND: Transmission of SARS-CoV-2 from humans to other mammals, including pet animals, has been reported. However, with the exception of farmed mink, there is no previous evidence that these infected animals can infect humans, resulting in sustained human-to-human transmission. Following a confirmed SARS-CoV-2 infection of a pet shop worker, animals in the shop and the warehouse supplying it were tested for evidence of SARS-CoV-2 infection. METHODS: In this case study, viral swabs and blood samples were collected from animals in a pet shop and its corresponding warehouse in Hong Kong. Nasal swab or saliva samples from human COVID-19 patients epidemiologically linked to the pet shop and from subsequent local cases confirmed to be infected by SARS-CoV-2 delta variant were collected. Oral swabs were tested by quantitative RT-PCR (RT-qPCR) for SARS-CoV-2 and blood samples were serologically tested by a surrogate virus neutralisation test and plaque reduction neutralisation test. The SARS-CoV-2 RT-qPCR positive samples were sequenced by next generation viral full genome sequencing using the ISeq sequencing platform (Illumina), and the viral genomes were phylogenetically analysed. FINDINGS: Eight (50%) of 16 individually tested Syrian hamsters in the pet shop and seven (58%) of 12 Syrian hamsters in the corresponding warehouse were positive for SARS-CoV-2 infection in RT-qPCR or serological tests. None of the dwarf hamsters (n=75), rabbits (n=246), guinea pigs (n=66), chinchillas (n=116), and mice (n=2) were confirmed positive for SARS-CoV-2 in RT-qPCR tests. SARS-CoV-2 viral genomes deduced from human and hamster cases in this incident all belong to the delta variant of concern (AY.127) that had not been circulating locally before this outbreak. The viral genomes obtained from hamsters were phylogenetically related with some sequence heterogeneity. Phylogenetic dating suggests infection in these hamsters occurred around Oct 14, 2021 (95% CI Sept 15 to Nov 9, 2021). Multiple zoonotic transmission events to humans were detected, leading to onward human-to-human transmission. INTERPRETATION: Pet hamsters can be naturally infected with SARS-CoV-2. The virus can circulate among hamsters and lead to human infections. Both genetic and epidemiological results strongly suggest that there was more than one hamster-to-human transmission event in this study. This incident also led to onward human transmission. Importation of SARS-CoV-2-infected hamsters was a likely source of this outbreak. FUNDING: US National Institutes of Health, Research Grants Council of Hong Kong, Food and Health Bureau, and InnoHK.


Subject(s)
COVID-19/veterinary , Cricetinae/virology , SARS-CoV-2 , Viral Zoonoses/transmission , Adult , Animals , COVID-19/epidemiology , COVID-19/transmission , COVID-19 Nucleic Acid Testing , Child , Disease Outbreaks , Female , Hong Kong/epidemiology , Humans , Male , Pets/virology , Phylogeny
17.
Nat Commun ; 13(1): 1155, 2022 03 03.
Article in English | MEDLINE | ID: covidwho-1730286

ABSTRACT

Many locations around the world have used real-time estimates of the time-varying effective reproductive number ([Formula: see text]) of COVID-19 to provide evidence of transmission intensity to inform control strategies. Estimates of [Formula: see text] are typically based on statistical models applied to case counts and typically suffer lags of more than a week because of the latent period and reporting delays. Noting that viral loads tend to decline over time since illness onset, analysis of the distribution of viral loads among confirmed cases can provide insights into epidemic trajectory. Here, we analyzed viral load data on confirmed cases during two local epidemics in Hong Kong, identifying a strong correlation between temporal changes in the distribution of viral loads (measured by RT-qPCR cycle threshold values) and estimates of [Formula: see text] based on case counts. We demonstrate that cycle threshold values could be used to improve real-time [Formula: see text] estimation, enabling more timely tracking of epidemic dynamics.


Subject(s)
COVID-19/transmission , SARS-CoV-2 , Viral Load , Basic Reproduction Number/statistics & numerical data , COVID-19/epidemiology , COVID-19/virology , Computer Simulation , Computer Systems , Epidemics , Hong Kong/epidemiology , Humans , Models, Statistical , Pandemics , Viral Load/statistics & numerical data
18.
BMJ Open ; 11(12): e055909, 2021 12 20.
Article in English | MEDLINE | ID: covidwho-1723806

ABSTRACT

OBJECTIVES: This study aims to explore the attenuated impact of reported avoidance behaviours adherence on the transmission of COVID-19 through cross-sectional surveys in Hong Kong, in order to make up for the lack of research on avoidance behaviours fatigue. DESIGN: 40 cross-sectional telephone surveys. SETTING: All districts in Hong Kong. PARTICIPANTS: 31 332 Cantonese or English-speaking participants at age of 18 years or above. METHODS: We collected data on behaviours and estimated the average effective reproduction number ([Formula: see text]) among the Hong Kong adult population during the COVID-19 epidemic wave in November-December 2020 and compared with the preceding epidemic in June-July 2020. RESULTS: We observed a reduction in adherence to voluntary avoidance behaviours due to pandemic fatigue, but continued adherence to regulated avoidance behaviours. The average [Formula: see text] during the post-work from home period was higher in November-December wave with estimated [Formula: see text] of 0.81 (95% CI: 0.75 to 0.87) compared with the June-July wave with an [Formula: see text] of 0.67 (95% CI: 0.60 to 0.75). CONCLUSIONS: The declined effectiveness of social distancing interventions in reducing COVID-19 transmission was associated with fatigue with voluntary avoidance behaviours in Hong Kong population, implying a need for the government to reinvigorate the public to maintain effective pandemic control.


Subject(s)
COVID-19 , Pandemics , Adolescent , Adult , Avoidance Learning , Cross-Sectional Studies , Fatigue/epidemiology , Fatigue/prevention & control , Hong Kong/epidemiology , Humans , SARS-CoV-2 , Surveys and Questionnaires , Telephone
19.
Emerg Infect Dis ; 28(3): 759-761, 2022 03.
Article in English | MEDLINE | ID: covidwho-1705733

ABSTRACT

Controlling transmission in restaurants is an important component of public health and social measures for coronavirus disease. We examined the effects of restaurant measures in Hong Kong. Our findings indicate that shortening operating hours did not have an effect on time-varying effective reproduction number when capacity was already reduced.


Subject(s)
COVID-19 , Basic Reproduction Number , COVID-19/prevention & control , Hong Kong/epidemiology , Humans , Restaurants , SARS-CoV-2
20.
Nat Rev Phys ; 2(6): 279-281, 2020.
Article in English | MEDLINE | ID: covidwho-1684119

ABSTRACT

As the COVID-19 pandemic continues, mathematical epidemiologists share their views on what models reveal about how the disease has spread, the current state of play and what work still needs to be done.

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