Background A range of public health measures have been implemented to suppress local transmission of coronavirus disease 2019 (COVID-19) in Hong Kong. We examined the effect of these interventions and behavioural changes of the public on the incidence of COVID-19, as well as on influenza virus infections, which might share some aspects of transmission dynamics with COVID-19. MethodsWe analysed data on laboratory-confirmed COVID-19 cases, influenza surveillance data in outpatients of all ages, and influenza hospitalisations in children. We estimated the daily effective reproduction number (R t ) for COVID-19 and influenza A H1N1 to estimate changes in transmissibility over time. Attitudes towards COVID-19 and changes in population behaviours were reviewed through three telephone surveys done on Jan 20-23, Feb 11-14, and March 10-13, 2020.Findings COVID-19 transmissibility measured by R t has remained at approximately 1 for 8 weeks in Hong Kong. Influenza transmission declined substantially after the implementation of social distancing measures and changes in population behaviours in late January, with a 44% (95% CI 34-53%) reduction in transmissibility in the community, from an estimated R t of 1•28 (95% CI 1•26-1•30) before the start of the school closures to 0•72 (0•70-0•74) during the closure weeks. Similarly, a 33% (24-43%) reduction in transmissibility was seen based on paediatric hospitalisation rates, from an R t of 1•10 (1•06-1•12) before the start of the school closures to 0•73 (0•68-0•77) after school closures. Among respondents to the surveys, 74•5%, 97•5%, and 98•8% reported wearing masks when going out, and 61•3%, 90•2%, and 85•1% reported avoiding crowded places in surveys 1 (n=1008), 2 (n=1000), and 3 (n=1005), respectively. InterpretationOur study shows that non-pharmaceutical interventions (including border restrictions, quarantine and isolation, distancing, and changes in population behaviour) were associated with reduced transmission of COVID-19 in Hong Kong, and are also likely to have substantially reduced influenza transmission in early February, 2020.

Hong Kong has been severely affected by severe acute respiratory syndrome (SARS). Contact in households and health-care settings is thought to be important for transmission, putting children at particular risk. Most data so far, however, have been for adults. We prospectively followed up the first ten children with SARS managed during the early phase of the epidemic in Hong Kong. All the children had been in close contact with infected adults. Persistent fever, cough, progressive radiographic changes of chest and lymphopenia were noted in all patients. The children were treated with high-dose ribavirin, oral prednisolone, or intravenous methylprednisolone, with no short-term adverse effects. Four teenagers required oxygen therapy and two needed assisted ventilation. None of the younger children required oxygen supplementation. Compared with adults and teenagers, SARS seems to have a less aggressive clinical course in younger children.

The SARS-CoV-2 pandemic poses the greatest global public health challenge in a century. Neutralizing antibody is a correlate of protection and data on kinetics of virus neutralizing antibody responses are needed. We tested 293 sera from an observational cohort of 195 reverse transcription polymerase chain reaction (RT-PCR) confirmed SARS-CoV-2 infections collected from 0 to 209 days after onset of symptoms. Of 115 sera collected ≥61 days after onset of illness tested using plaque reduction neutralization (PRNT) assays, 99.1% remained seropositive for both 90% (PRNT90) and 50% (PRNT50) neutralization endpoints. We estimate that it takes at least 372, 416 and 133 days for PRNT50 titres to drop to the detection limit of a titre of 1:10 for severe, mild and asymptomatic patients, respectively. At day 90 after onset of symptoms (or initial RT-PCR detection in asymptomatic infections), it took 69, 87 and 31 days for PRNT50 antibody titres to decrease by half (T1/2) in severe, mild and asymptomatic infections, respectively. Patients with severe disease had higher peak PRNT90 and PRNT50 antibody titres than patients with mild or asymptomatic infections. Age did not appear to compromise antibody responses, even after accounting for severity. We conclude that SARS-CoV-2 infection elicits robust neutralizing antibody titres in most individuals.

Background The coronavirus disease 2019 (COVID-19) pandemic is having a profound impact on the health and development of children worldwide. There is limited evidence on the impact of COVID-19 and its related school closures and disease-containment measures on the psychosocial wellbeing of children; little research has been done on the characteristics of vulnerable groups and factors that promote resilience. Methods We conducted a large-scale cross-sectional population study of Hong Kong families with children aged 2–12 years. Parents completed an online survey on family demographics, child psychosocial wellbeing, functioning and lifestyle habits, parent–child interactions, and parental stress during school closures due to COVID-19. We used simple and multiple linear regression analyses to explore factors associated with child psychosocial problems and parental stress during the pandemic. Results The study included 29,202 individual families; of which 12,163 had children aged 2–5 years and 17,029 had children aged 6–12 years. The risk of child psychosocial problems was higher in children with special educational needs, and/or acute or chronic disease, mothers with mental illness, single-parent families, and low-income families. Delayed bedtime and/or inadequate sleep or exercise duration, extended use of electronic devices were associated with significantly higher parental stress and more psychosocial problems among pre-schoolers. Conclusions This study identifies vulnerable groups of children and highlights the importance of strengthening family coherence, adequate sleep and exercise, and responsible use of electronic devices in promoting psychosocial wellbeing during the COVID-19 pandemic. Electronic supplementary material The online version of this article (10.1007/s00787-020-01680-8) contains supplementary material, which is available to authorized users.

Viral shedding profile of infections caused by the pandemic H1N1 2009 influenza A virus has not been reported. The aim of this study was to determine the viral load in different body sites. Viral loads of pandemic H1N1 virus in respiratory specimens, stool, urine, and serum were determined by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). Respiratory specimens from patients with seasonal influenza were used as historical controls. Initial pre-treatment viral load were compared between these two groups. Serial respiratory specimens from patients with pandemic H1N1 virus infection were obtained for analysis of viral dynamics. Twenty-two pandemic H1N1 cases and 44 seasonal influenza historical controls were included. The mean initial viral load before oseltamivir therapy was 1.84 x 10(8) copies/ml for pandemic H1N1 virus compared with 3.28 x 10(8) copies/ml in seasonal influenza historical controls (P = 0.085). Among patients with pandemic H1N1 virus infection, peak viral load occurred on the day of onset of symptoms, and declined gradually afterwards, with no virus being detectable in respiratory specimens by RT-PCR 8 days and by culture 5 days after the onset of symptoms respectively, except in one patient. Pandemic H1N1 virus was detected in stool and in urine from 4/9 and 1/14 patients, respectively. Viral culture was also positive from the stool sample with the highest viral load. Younger age was associated with prolonged shedding in the respiratory tract and higher viral load in the stool. Data from this quantitative analysis of viral shedding may have implications for formulating infection control measures.

ABSTRACT. Objective. To study the epidemiologic, clinical, laboratory, and radiologic features, prognostic indicators, and short-term to medium-term outcomes for children with severe acute respiratory syndrome (SARS) and to validate the performance characteristics of a clinical case definition, calculated with respect to SARSassociated coronavirus (SARS-CoV) seroconversion.Methods. Children <18 years of age, from a singlesite outbreak, who satisfied a clinical case definition for SARS, with subsequent serologic confirmation, were treated according to a standard protocol and prospectively monitored.Results. Forty-four children were included. The median age was 12 years. Forty-two children (95.5%) demonstrated an epidemiologic link. Fever, cough, malaise, coryza, sputum production, headache, myalgia, lymphopenia, and elevated lactate dehydrogenase levels were common presenting features. Radiographic findings were nonspecific, but high-resolution computed tomography of the thorax was an early diagnostic aid. A specific reverse transcription-polymerase chain reaction assay for SARS-CoV yielded positive results for <50% of children. Of 9 children who developed hypoxemia, 8 were treated with methylprednisolone. Of 5 children who received intensive care, 3 required assisted ventilation. All children recovered, and serious adverse events in response to treatment were not observed. The outcomes at 3 to 6 months after disease onset, including exercise tolerance, pulmonary functions, and psychologic status, were favorable. An age of >12 years was associated with methylprednisolone therapy for severe illness. After exclusion of the only infant, an age of >12 years was associated with oxygen requirements. Sore throat, high neutrophil count at presentation, and peak neutrophilia were independent factors predicting severe illness. The clinical case definition demonstrated good sensitivity, specificity, and positive and negative predictive values (97.8%, 92.7%, 88%, and 98.7%, respectively) for diagnostic accuracy.Conclusions. 1 Although the majority were adults, 121 children (6.9%) Ͻ18 years of age were registered, yielding an age-specific attack rate of 8.9 cases per 100 000 persons Ͻ18 years of age and a case fatality rate of 0%. A total of 89 hospitalized children in Hong Kong demonstrated serologic evidence of infection by the SARS-associated coronavirus (SARS-CoV) (e-SARS database, Hospital Authority, Hong Kong Special Administrative Region, data on file).Published articles on pediatric SARS have focused on reporting the demographic, clinical, laboratory, and radiologic characteristics. Definitive virologic data, prognostic indicators, and short-term to medium-term follow-up information were lacking in those preliminary reports. [2][3][4] We prospectively monitored a cohort of 44 children with laboratory confirmation of SARS who were treated at a referral center for pediatric infectious diseases that admitted the largest number of pediatric patients with SARS in Hong Kong. Their epidemiologic links; clinical, laboratory,...

BackgroundThe impacts of social restrictions for COVID-19 on children’s vision and lifestyle remain unknown.AimsTo investigate myopia incidence, spherical equivalent refraction (SER) and lifestyle changes among schoolchildren during the COVID-19 pandemic.MethodsTwo separate longitudinal cohorts of children aged 6–8 years in Hong Kong were included. The COVID-19 cohort was recruited at the beginning of the COVID-19 outbreak, whereas the pre-COVID-19 cohort was recruited before the COVID-19 pandemic. All children received ocular examinations, and answered a standardised questionnaire relating to their lifestyle, including time spent on outdoor activities and near work, both at baseline and at follow-up visits.ResultsA total of 1793 subjects were recruited, of whom 709 children comprised the COVID-19 cohort with 7.89±2.30 months of follow-up, and 1084 children comprised the pre-COVID-19 cohort with 37.54±3.12 months of follow-up. The overall incidence was 19.44% in the COVID-19 cohort, and 36.57% in pre-COVID-19 cohort. During the COVID-19 pandemic, the change in SER and axial length was –0.50±0.51 D and 0.29±0.35 mm, respectively; the time spent on outdoor activities decreased from 1.27±1.12 to 0.41±0.90 hours/day (p<0.001), while screen time increased from 2.45±2.32 to 6.89±4.42 hours/day (p<0.001).ConclusionsWe showed a potential increase in myopia incidence, significant decrease in outdoor time and increase in screen time among schoolchildren in Hong Kong during the COVID-19 pandemic. Our results serve to warn eye care professionals, and also policy makers, educators and parents, that collective efforts are needed to prevent childhood myopia—a potential public health crisis as a result of COVID-19.

SARS-CoV-2 infection of children leads to a mild illness and the immunological differences with adults are unclear. Here, we report SARS-CoV-2 specific T cell responses in infected adults and children and find that the acute and memory CD4+ T cell responses to structural SARS-CoV-2 proteins increase with age, whereas CD8+ T cell responses increase with time post-infection. Infected children have lower CD4+ and CD8+ T cell responses to SARS-CoV-2 structural and ORF1ab proteins when compared with infected adults, comparable T cell polyfunctionality and reduced CD4+ T cell effector memory. Compared with adults, children have lower levels of antibodies to β-coronaviruses, indicating differing baseline immunity. Total T follicular helper responses are increased, whilst monocyte numbers are reduced, indicating rapid adaptive co-ordination of the T and B cell responses and differing levels of inflammation. Therefore, reduced prior β-coronavirus immunity and reduced T cell activation in children might drive milder COVID-19 pathogenesis.