Transmission and containment of the SARS-CoV-2 Delta variant of concern in Guangzhou, China: A population-based study.

BACKGROUND: The first community transmission of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Delta variant of concern (VOC) in Guangzhou, China occurred between May and June 2021. Herein, we describe the epidemiological characteristics of this outbreak and evaluate the implemented containment measures against this outbreak. METHODOLOGY/PRINCIPAL FINDINGS: Guangzhou Center for Disease Control and Prevention provided the data on SARS-CoV-2 infections reported between 21 May and 24 June 2021. We estimated the incubation period distribution by fitting a gamma distribution to the data, while the serial interval distribution was estimated by fitting a normal distribution. The instantaneous effective reproductive number (Rt) was estimated to reflect the transmissibility of SARS-CoV-2. Clinical severity was compared for cases with different vaccination statuses using an ordinal regression model after controlling for age. Of the reported local cases, 7/153 (4.6%) were asymptomatic. The median incubation period was 6.02 (95% confidence interval [CI]: 5.42-6.71) days and the means of serial intervals decreased from 5.19 (95% CI: 4.29-6.11) to 3.78 (95% CI: 2.74-4.81) days. The incubation period increased with age (P<0.001). A hierarchical prevention and control strategy against COVID-19 was implemented in Guangzhou, with Rt decreasing from 6.83 (95% credible interval [CrI]: 3.98-10.44) for the 7-day time window ending on 27 May 2021 to below 1 for the time window ending on 8 June and thereafter. Individuals with partial or full vaccination schedules with BBIBP-CorV or CoronaVac accounted for 15.3% of the COVID-19 cases. Clinical symptoms were milder in partially or fully vaccinated cases than in unvaccinated cases (odds ratio [OR] = 0.26 [95% CI: 0.07-0.94]). CONCLUSIONS/SIGNIFICANCE: The hierarchical prevention and control strategy against COVID-19 in Guangzhou was timely and effective. Authorised inactivated vaccines are likely to contribute to reducing the probability of developing severe disease. Our findings have important implications for the containment of COVID-19.

Effect of meteorological factors on scarlet fever incidence in Guangzhou City, Southern China, 2006-2017.

OBJECTIVE: To explore the relationship between meteorological factors and scarlet fever incidence from 2006 to 2017 in Guangzhou, the largest subtropical city of Southern China, and assist public health prevention and control measures. METHODS: Data for weekly scarlet fever incidence and meteorological variables from 2006 to 2017 in Guangzhou were collected from the National Notifiable Disease Report System (NNDRS) and the Guangzhou Meteorological Bureau (GZMB). Distributed lag nonlinear models (DLNMs) were conducted to estimate the effect of meteorological factors on weekly scarlet fever incidence in Guangzhou. RESULTS: We observed nonlinear effects of temperature, relative humidity, and wind velocity. The risk was the highest when the weekly mean temperature was 31 °C during lag week 14, yielding a relative risk (RR) of 1.48 (95% CI: 1.01-2.17). When relative humidity was 43.5% during lag week 0, the RR was 1.49 (95% CI: 1.04-2.12); the highest RR (1.55, 95% CI: 1.20-1.99) was reached when relative humidity was 93.5% during lag week 20. When wind velocity was 4.4 m/s during lag week 13, the RR was highest at 3.41 (95% CI: 1.57-7.44). Positive correlations were observed among weekly temperature ranges and atmospheric pressure with scarlet fever incidence, while a negative correlation was detected with aggregate rainfall. The cumulative extreme effect of meteorological variables on scarlet fever incidence was statistically significant, except for the high effect of wind velocity. CONCLUSION: Weekly mean temperature, relative humidity, and wind velocity had double-trough effects on scarlet fever incidence; high weekly temperature range, high atmospheric pressure, and low aggregate rainfall were risk factors for scarlet fever morbidity. Our findings provided preliminary, but fundamental, information that may be useful for a better understanding of epidemic trends of scarlet fever and for developing an early warning system. Laboratory surveillance for scarlet fever should be strengthened in the future.

[Evaluation on the risks of H5, H7 and H9 avian influenza infections in Guangzhou: using data from the 2006-2012 avian influenza surveillance program].

OBJECTIVE: To analyze the results of avian influenza surveillance program in Guangzhou from 2006 to 2012 and to evaluate the risk of infections with H5, H7 and H9 subtypes avian influenza viruses. METHODS: Avian influenza surveillance system in Guangzhou consisted five components:serum surveillance on occupational population, environmental specimen surveillance of avian influenza virus, avian flu emergency surveillance, influenza viruses surveillance on ILI patient and surveillance on pneumonia of unknown causes. Hemagglutination inhibition test was conducted to detect the antibodies against H5, H7 and H9 while RT-PCR was used to test the nucleic acid of H5, H7 and H9 viruses. RESULTS: From 2006 to 2012, 4103 serum specimens were collected from occupational populations and the overall positive rate of H5/H7/H9 antibodies was 3.82% . The antibody positive rates for H5, H7 and H9 were 0.22% ,0.00% and 3.70% respectively. 4 serum specimens for H5 and H9 simultaneously showed antibody positive. The positive rate of H9 among occupational populations(4.21%)appeared higher than that from the control population(2.16%). 2028 specimens were collected from poultry sites and 55 samples found positive for H5 nucleic acid (positive rate:2.71%), 14 samples positive for H9 nucleic acid (positive rate:0.69%), 5 specimens, simultaneously positive for H5 and H9 nucleic acids. However, none of the samples showing H7 nucleic acid positive. From 2006 to 2012, all the tested H5/H7/H9 virus were negative from the respiratory/serum specimens among those close contacts of patients or high risk groups through the avian flu emergency surveillance program,ILI patient influenza virus surveillance programs or pneumonia of unknown causes surveillance program. CONCLUSION: Contamination of H5/H9 avian influenza virus did exist in the poultry sites in Guangzhou, especially in the wet Markets. The H5/H9 avian influenza virus caused asymptomatic infection was proved to be existed within the population exposed to the poultry, suggesting that the poultry occupational population in Guangzhou was under the risk of avian influenza virus infection.

[Study on epidemic characteristics and etiology of community acquired pneumonia in Guangzhou from 2009 to 2012].

OBJECTIVE: To investigate the epidemic characteristics and pathogenic spectrum of community acquired pneumonia (CAP) in Guangzhou from 2009 to 2012. METHOD: 14 major comprehensive hospitals were selected from 11 districts as sentinel hospitals for CAP cases surveillance, including 18 982 223 in total during the 4 years. The characteristics of pathogenic spectrum of CAP were stratified and analyzed by year, age and season. RESULTS: 18 982 223 cases were included in the surveillance from year 2009 to 2012, in which 56 618 cases were CAP. The number of CAP cases increased from 8677 in year 2009 to 19 947 in year 2012 in Guangzhou; while the percentage of visits for CAP raised from 0.22% (8677/3 893 800) to 0.41% (19 947/4 839 766). The difference showed statistical significance (χ(2) = 2693.00, P < 0.05). Among the hospitalized CAP cases, 66.05% (10 954/16 585) were aged ≤ 5 years old or > 66 years old. The percentage of cases infected by a single pathogen was 88.11% (14 613/16 585), while co-infected cases accounted for 4.17% (691/16 585). Bacteria accounted for the largest proportion of 65.25% (10 821/16 585) as a single pathogen, followed by mycoplasma 13.54% (2245/16 585), virus 9.01% (1494/16 585) and chlamydia 0.32% (53/16 585). The proportion of virus infection was increasing from 4.74% to 11.64%. The difference showed statistical significance (χ(2) = 135.32, P < 0.05). Bacteria infection was the leading causes for CAP cases in all age groups; however the percentage increased with the increasing of ages. The rate of bacterial infection was increased from 48.35% (2993/6191) among children aged ≤ 5 years old to 81.31% (3873/4763) among adults aged over 65 years (χ(2) = 1632.00, P < 0.05). The rate of atypical pathogens (mycoplasma, chlamydia) for children ( ≤ 15 years old) (25.99%, 1805/6945) was higher than that for adults aged ≥ 16 years old (5.12%, 494/9640) (χ(2) = 2.11, P < 0.05). The effect from season on the pathogenic spectrum was not observed.433 hospitalized CAP cases were dead from 2009 to 2012. Case fatality rate was highest among people aged over 65 years old (4.70%, 224/4763) and lowest among children aged between 6 to 15 years old (0.27%, 2/754). CONCLUSION: The incidence of community acquired pneumonia was rising in Guangzhou from 2009 to 2012. Bacteria was the dominant pathogen. Children and old people were the high-risk population of community acquired pneumonia; while co-infection was still at low level.

[Association between risk factors of cardiovascular diseases and osteoporosis in postmenopausal Chinese women].

OBJECTIVE: To assess the relationship between cardiovascular risk factors and osteoporosis. METHODS: 2202 women aged 50 - 73 years were included in this cross-sectional study from the communities in Guangzhou, from July 2008 to January 2010. Cardiovascular risk factors including age, years since menopause, physical activity, anthropometrics, body composition, blood pressure, fasting serum lipids, glucose and uric acid, intima-media thickness (IMT) of carotid artery were assessed. Ultrasonic bone density (speed of sound) at the radius and tibia were determined. Osteoporosis was defined as T-score ≤ -2.5. Common factors for the cardiovascular risk factors were extracted using the factor analysis method. RESULTS: Eight common factors representing obesity, lean mass, blood triglycerides and uric acid, cholesterol, age, blood pressure, IMT and physical activity were extracted. Data from the Multivariate logistic regression showed a dose-dependent association of greater scores of age and IMT factors and lower score of lean mass factor with the increased risk of osteoporosis at the radius and tibia. As compared with the bottom quartile, the OR (95%CI) of radius and tibia osteoporosis were 0.62 (0.44 - 0.88) and 0.62 (0.48 - 0.80) for lean mass factor, 4.02 (2.72 - 5.94) and 3.68 (2.81 - 4.82) for age factor, 1.41 (1.00 - 2.00) and 1.54 (1.19 - 2.00) for IMT factors, respectively. Moreover, greater blood pressure score was associated with higher risk of radius osteoporosis while the higher obese score, was correlated with the increased risk of tibia osteoporosis. CONCLUSION: The cardiovascular-related risk factors of greater IMT, obesity, blood pressure and lower lean mass scores were associated with increased osteoporosis risks while called for more concern among the Chinese women.

[Study on food preference and dietary behavior to overweight/obesity in school children and adolescents in Guangzhou: a case-control study].

OBJECTIVE: This study assessed the effect of food preference and dietary behaviors on the risk of overweight or obesity in school children and adolescents aged 6 - 19 years. METHODS: All overweight or obese students, with age- and school-matched controls were recruited for this case-control study from 28 elementary and secondary schools in Guangzhou urban districts from October 2006 to April 2007. Weight and height were measured, and body mass index was calculated for the classification of obesity, overweight and underweight. Their food preference and behaviors were assessed using a structured questionnaire completed by their parents. Behavior and food preference were classified into four levels, and the relevant bottom levels were defined as control groups. Logistic regression was used to assess independent determinants of overweight and obesity. RESULTS: Among 7136 participants, 1947 cases and 2136 normal weight controls from 5755 students with valid questionnaire data were included in the study. Results from univariate analysis showed that odds ratios for overweight or obesity were 0.60-0.69 in those with most preference (top group) on vegetables, fruits, candy, evening snacks, 0.50 in the students of less food partiality, 1.84, 1.30 and 1.26 in those of most preference for pork, beef and deep-fried foods, and 5.14 in students with fastest speed during eating, respectively (all P < 0.05). Vegetable intake, evening snacks preference, speed during eating and food partiality remained with significant association with overweight and obesity in multivariate analysis after adjusted for age, sex, family socio-economical status and their parents' body build. The adjusted odds ratios (OR) and 95% confidence intervals (95%CI) of the above items became 0.55 (0.42 - 0.73), 0.48 (0.35 - 0.65), 0.50 (0.39 - 0.65), and 4.32 (3.23 - 5.80) as compared to the relevant lowest categories, respectively. CONCLUSION: Behaviors as eating more vegetables and slow-eating might be protective factors against overweight and obesity in school children.