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Background: Since the identification in early 2013 of severe disease caused by influenza A(H7N9) virus infection, there have been few attempts to characterize the full severity profile of human infections. Our objective was to estimate the number and severity of H7N9 infections in Guangzhou, using a serological study. Methods: We collected residual sera from patients of all ages admitted to a hospital in the city of Guangzhou in southern China in 2013 and 2014. We screened the sera using a haemagglutination inhibition assay against a pseudovirus containing the H7 and N9 of A/Anhui/1/2013(H7N9), and samples with a screening titer ≥10 were further tested by standard hemagglutination-inhibition and virus neutralization assays for influenza A(H7N9). We used a statistical model to interpret the information on antibody titers in the residual sera, assuming that the residual sera provided a representative picture of A(H7N9) infections in the general population, accounting for potential cross-reactions. Results: We collected a total of 5360 residual sera from December 2013 to April 2014 and from October 2014 to December 2014, and found two specimens that tested positive for H7N9 antibody at haemagglutination inhibition titer ≥40 and a neutralization titer ≥40. Based on this, we estimated that 64,000 (95% credibility interval: 7300, 190,000) human infections with influenza A(H7N9) virus occurred in Guangzhou in early 2014, with an infectionfatality risk of 3.6 deaths (95% credibility interval: 0.47, 15) per 10,000 infections. Conclusions: Our study suggested that the number of influenza A(H7N9) virus infections in Guangzhou substantially exceeded the number of laboratory-confirmed cases there, albeit with considerable imprecision. Our study was limited by the small number of positive specimens identified, and larger serologic studies would be valuable. Our analytic framework would be useful if larger serologic studies are done. [ABSTRACT FROM AUTHOR]

Background: A novel avian-origin influenza A(H7N9) caused a major outbreak in Mainland China in early 2013. Exposure to live poultry was believed to be the major route of infection. There are limited data on how the general public changes their practices regarding live poultry exposure in response to the early outbreak of this novel influenza and the frequency of population exposure to live poultry in different areas of China. Methodology: This study investigated population exposures to live birds from various sources during the outbreak of H7N9 in Guangzhou city, China in 2013 and compared them with those observed during the 2006 influenza A(H5N1) outbreak. Adults were telephone-interviewed using two-stage sampling, stratified by three residential areas of Guangzhou: urban areas and two semi-rural areas in one of which (Zengcheng) A(H7N9) virus was detected in a chicken from wet markets. Logistic regression models were built to describe practices protecting against avian influenza, weighted by age and gender, and then compare these practices across residential areas in 2013 with those from a comparable 2006 survey. Principal Findings: Of 1196 respondents, 45% visited wet markets at least daily and 22.0% reported buying live birds from wet markets at least weekly in April-May, 2013, after the H7N9 epidemic was officially declared in late March 2013. Of those buying live birds, 32.3% reported touching birds when buying and 13.7% would slaughter the poultry at home. Although only 10.1% of the respondents reported raising backyard birds, 92.1% of those who did so had physical contact with the birds they raised. Zengcheng respondents were less likely to report buying live birds from wet markets, but more likely to buy from other sources when compared to urban respondents. Compared with the 2006 survey, the prevalence of buying live birds from wet markets, touching when buying and slaughtering birds at home had substantially declined in the 2013 survey. Conclusion/Significance: Although population exposures to live poultry were substantially fewer in 2013 compared to 2006, wet markets and backyard poultry remained the two major sources of live bird exposures for the public in Guangzhou in 2013. Zengcheng residents seemed to have reduced buying live birds from wet markets but not from other sources in response to the detection of H7N9 virus in wet markets. [ABSTRACT FROM AUTHOR]

Background Live poultry traders (LPTs) have greater risk to avian influenza due to occupational exposure to poultry. This study investigated knowledge, attitudes and practices of LPTs relating to influenza A (H7N9). Methods Using multi-stage cluster sampling, 306 LPTs were interviewed in Guangzhou by a standardized questionnaire between mid-May to June, 2013. Hierarchical logistic regression models were used to identify factors associated with preventive practices and attitudes towards various control measures implemented in live poultry markets against H7N9. Results Only 46.1% of the respondents recognized risks associated with contacts with bird secretions or droppings, and only 22.9% perceived personally "likely/very likely" to contract H7N9 infection. Around 60% of the respondents complied with hand-washing and wearing gloves, and only 20% reported wearing face masks. Only 16.3% of the respondents agreed on introducing central slaughtering of poultry. Being younger, involving in slaughtering poultry, having longer working hours, less access to H7N9-related information and poorer knowledge, and perceiving lower personal susceptibility to H7N9 infection were negatively associated with preventive practices. Comparing with previous studies conducted when human cases of H5N1 avian influenza infection was first identified in Guangdong, LPTs' perceived susceptibility to novel influenza viruses increased significantly but acceptance for central slaughtering of poultry remained low. Conclusions Information on avian influenza provided through multiple communication tools may be necessary to promote knowledge among poultry traders. Familiarity with risk may have led to the lower perceived vulnerability to avian influenza and less protective actions among the LPTs particularly for those involving more risky exposure to live poultry. Reasons for the consistently low acceptance for central slaughtering of poultry await further exploration. [ABSTRACT FROM AUTHOR]

Although airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been recognized, the condition of ventilation for its occurrence is still being debated. We analyzed a coronavirus disease 2019 (COVID-19) outbreak involving three families in a restaurant in Guangzhou, China, assessed the possibility of airborne transmission, and characterized the associated environmental conditions. We collected epidemiological data, obtained a full video recording and seating records from the restaurant, and measured the dispersion of a warm tracer gas as a surrogate for exhaled droplets from the index case. Computer simulations were performed to simulate the spread of fine exhaled droplets. We compared the in-room location of subsequently infected cases and spread of the simulated virus-laden aerosol tracer. The ventilation rate was measured using the tracer gas concentration decay method. This outbreak involved ten infected persons in three families (A, B, C). All ten persons ate lunch at three neighboring tables at the same restaurant on January 24, 2020. None of the restaurant staff or the 68 patrons at the other 15 tables became infected. During this occasion, the measured ventilation rate was 0.9 L/s per person. No close contact or fomite contact was identified, aside from back-to-back sitting in some cases. Analysis of the airflow dynamics indicates that the infection distribution is consistent with a spread pattern representative of long-range transmission of exhaled virus-laden aerosols. Airborne transmission of the SARS-CoV-2 virus is possible in crowded space with a ventilation rate of 1 L/s per person. [Display omitted] • This outbreak involved ten infected persons in three families. • Full video recording at time of infection allows restoration of the scene. • Time-averaged ventilation rates were only 0.9 L/s per person in the restaurant. • Insufficient ventilation played a role in this outbreak of COVID-19. [ABSTRACT FROM AUTHOR]