Influenza-associated mortality in Yancheng, China, 2011-15

Introduction: The Yangtze river delta in eastern China, centred on Shanghai, is one of the most populated regions of the world with more than 100 million residents. We examined the impact of influenza on excess mortality in Yancheng, a prefecture-level city with 8.2 million population located 250km north of Shanghai, during 2011-2015. Methods: We obtained individual data on deaths by date, age, sex and cause in Yancheng from the Chinese Centers for Disease Control and Prevention, and used these to derive weekly rates of mortality from respiratory causes, respiratory and cardiovascular causes combined, and all causes. We used data on influenza-like illnesses and laboratory detections of influenza to construct a proxy measure of the weekly incidence of influenza virus infections in the community. We used regression models to estimate the association of influenza activity with mortality and excess mortality by age, cause and influenza type/subtype. Results: We estimated that an annual average of 4.59 (95% confidence interval: 3.94, 7.41) excess respiratory deaths per 100,000 persons were associated with influenza, which was 4.6% of all respiratory deaths in the years studied. Almost all influenza-associated excess deaths occurred in persons ≥65 years. Influenza A(H3N2) had the greatest impact on mortality and was associated with around 50% of the influenza-associated respiratory deaths in the 5 years studied. Conclusions: Influenza has a substantial impact on respiratory mortality in Yancheng, mainly in older adults. Influenza vaccination has the potential to reduce disease burden, and cost-effectiveness analysis could be used to compare policy options.published_or_final_versio

Quantification of Influenza Virus RNA in Aerosols in Patient Rooms

The potential for human influenza viruses to spread through fine particle aerosols remains controversial. The objective of our study was to determine whether influenza viruses could be detected in fine particles in hospital rooms. METHODS AND FINDINGS: We sampled the air in 2-bed patient isolation rooms for four hours, placing cyclone samplers at heights of 1.5m and 1.0m. We collected ten air samples each in the presence of at least one patient with confirmed influenza A virus infection, and tested the samples by reverse transcription polymerase chain reaction. We recovered influenza A virus RNA from 5/10 collections (50%); 4/5 were from particles>4 μm, 1/5 from 1-4 μm, and none in particles<1 μm. CONCLUSIONS: Detection of influenza virus RNA in aerosols at low concentrations in patient rooms suggests that healthcare workers and visitors might have frequent exposure to airborne influenza virus in proximity to infected patients. A limitation of our study was the small sample size. Further studies should be done to quantify the concentration of viable influenza virus in healthcare settings, and factors affecting the detection of influenza viruses in fine particles in the air.published_or_final_versio

Viral shedding and transmission potential of asymptomatic and pauci-symptomatic influenza virus infections in the community

Influenza virus infections are associated with a wide spectrum of disease. However, few studies have investigated in detail the epidemiology and virology of asymptomatic and mild illness with influenza virus infections. METHODS: In a community-based study in Hong Kong from 2008 to 2014, we followed up initially healthy individuals who were household contacts of symptomatic persons with laboratory-confirmed influenza, to identify secondary infections. Information from daily symptom diaries was used to classify infections as symptomatic (with at least two signs/symptoms of: fever ≥37.8°C, headache, myalgia, cough, sore throat, runny nose and sputum), pauci-symptomatic (with one symptom only), or asymptomatic (reporting none of these symptoms). We compared the patterns of influenza viral shedding between these groups. RESULTS: We identified 235 virologically-confirmed secondary cases of influenza virus infection in the household setting, including 31 (13%) pauci-symptomatic and 25 (11%) asymptomatic cases. The duration of viral RNA shedding was shorter and declined more rapidly in pauci-symptomatic and asymptomatic cases compared with symptomatic cases. The mean levels of influenza viral RNA shedding in asymptomatic and pauci-symptomatic cases were approximately 1 to 2 log10 copies lower than in symptomatic cases. CONCLUSIONS: The presence of influenza viral shedding in influenza patients with very few or no symptoms reflects their potential for transmitting the virus to close contacts. These findings suggest that further research is needed to investigate the contribution of persons with asymptomatic or clinically mild influenza virus infections to influenza virus transmission in household, institutional, and community settings

Influenza virus RNA in aerosols in patient rooms

Parallel Session 6: New Advances in Diagnostic

Quantification of influenza virus RNA in aerosols in pediatrics patient rooms

Poster Sessions: no. P-101BACKGROUND: Children are considered as the key driver of influenza transmission, and the potential for human influenza viruses to spread through fine particle aerosols from children remains controversial. The objective of our study was to determine whether influenza viruses could be detected in fine particles in hospital pediatrics patient rooms. METHOD: We sampled the air in 5-bed pediatrics patient rooms for four hours, placing two cyclone air samplers at different distances from the bed with pediatrics patient with laboratory-confirmed influenza infection. We collected air samples in 3 size fractions, and tested the samples by reverse transcription polymerase chain reaction (RT-PCR). RESULTS: We collected air samples in 10 occasions with at least one pediatrics patient with laboratory-confirmed influenza infection in the patient room. We recovered influenza A virus RNA from 7/10 collections (70%): influenza A virus RNA can be recovered in particles>4µm in 7/10, in particles 1-4µm in 3/10, and in particles<1µm in 4/10 collections. CONCLUSION: Frequent detection of influenza virus RNA in aerosols in the proximity of pediatric patients suggests that children could have an important contribution to influenza transmission via the aerosol route