Short-Term Exposure to Ambient Air Pollution and Influenza: A Multicity Study in China.

BACKGROUND: Air pollution is a major risk factor for planetary health and has long been suspected of predisposing humans to respiratory diseases induced by pathogens like influenza viruses. However, epidemiological evidence remains elusive due to lack of longitudinal data from large cohorts. OBJECTIVE: Our aim is to quantify the short-term association of influenza incidence with exposure to ambient air pollutants in Chinese cities. METHODS: Based on air pollutant data and influenza surveillance data from 82 cities in China over a period of 5 years, we applied a two-stage time series analysis to assess the association of daily incidence of reported influenza cases with six common air pollutants [particulate matter with aerodynamic diameter ≤2.5µm (PM2.5), particulate matter with aerodynamic diameter ≤10µm (PM10), NO2, SO2, CO, and O3], while adjusting for potential confounders including temperature, relative humidity, seasonality, and holiday effects. We built a distributed lag Poisson model for one or multiple pollutants in each individual city in the first stage and conducted a meta-analysis to pool city-specific estimates in the second stage. RESULTS: A total of 3,735,934 influenza cases were reported in 82 cities from 2015 to 2019, accounting for 72.71% of the overall case number reported in the mainland of China. The time series models for each pollutant alone showed that the daily incidence of reported influenza cases was positively associated with almost all air pollutants except for ozone. The most prominent short-term associations were found for SO2 and NO2 with cumulative risk ratios of 1.094 [95% confidence interval (CI): 1.054, 1.136] and 1.093 (95% CI: 1.067, 1.119), respectively, for each 10 µg/m3 increase in the concentration at each of the lags of 1-7 d. Only NO2 showed a significant association with the daily incidence of influenza cases in the multipollutant model that adjusts all six air pollutants together. The impact of air pollutants on influenza was generally found to be greater in children, in subtropical cities, and during cold months. DISCUSSION: Increased exposure to ambient air pollutants, particularly NO2, is associated with a higher risk of influenza-associated illness. Policies on reducing air pollution levels may help alleviate the disease burden due to influenza infection. https://doi.org/10.1289/EHP12146.

Variability in transmission risk of SARS-CoV-2 in close contact settings: A contact tracing study in Shandong Province, China.

BACKGROUND: Understanding the relative transmissibility of SARS-CoV-2 virus across different contact settings and the possibility of superspreading events is important for prioritizing disease control. Such assessment requires proper consideration of individual level exposure history, which is made possible by contact tracing. METHODS: The case-ascertained study in Shandong, China including 97 laboratory-confirmed index cases and 3158 close contacts. All close contacts were quarantined after their last exposure of index cases. Contacts were tested for COVID-19 regularly by PCR to identify both symptomatic and asymptomatic infections. We developed a Bayesian transmission model to the contact tracing data to account for different duration of exposure among individuals to transmission risk in different settings, and the heterogeneity of infectivity of cases. RESULTS: We estimate secondary attack rates (SAR) to be 39% (95% credible interval (CrI): 20-64%) in households, 30% (95% CrI: 11-67%) in healthcare facilities, 23% (95% CrI: 7-51%) at workplaces, and 4% (95% CrI: 1-17%) during air travel. Models allowing heterogeneity of infectivity of cases provided a better goodness-of-fit. We estimated that 64% (95% CrI: 55-72%) of cases did not generate secondary transmissions, and 20% (95% CrI: 15-26%) cases explained 80% of secondary transmissions. CONCLUSIONS: Household, healthcare facilities and workplaces are efficient setting for transmission. Timely identification of potential superspreaders in most transmissible settings remains crucial for containing the pandemic.

The effect of influenza A (H1N1) pdm09 virus infection on cytokine production and gene expression in BV2 microglial cells.

Acute influenza infection has been reported to be associated with neurological symptoms such as influenza-associated encephalopathy (IAE). Although the pathophysiology of this condition remain unclear, neuroinflammation and associated alterations in the central nervous system (CNS) are usually induced. Microglia (MGs), CNS-resident macrophages, are generally the first cells to be activated in response to brain infection or damage. We performed reverse transcriptase droplet digital PCR (RT-ddPCR) and luminex assays to investigate virus proliferation and immune reactions in BV2 MGs infected with influenza A(H1N1)pdm09 virus. Furthermore, isobaric tags for relative and absolute quantitation (iTRAQ)-based quantitative proteomics methods were used to investigate the dynamic change in the protein expression profile in BV2 MGs to gain insight into the CNS response to influenza A (H1N1) pdm09 infection. Our results showed that the influenza A(H1N1)pdm09 virus was replicative and productive in BV2 MG cells, which produced cytokines such as interleukin (IL)-1ß, IL-6, tumour necrosis factor (TNF)-α and monocyte chemoattractant protein (MCP)-1. The expression of osteopontin (OPN) in the influenza A (H1N1) pdm09-infected BV2 MGs was upregulated at 16 and 32 h post-infection (hpi) compared to that in the control group, resulting in aggravated brain damage and inflammation. Our study indicates that OPN signalling might provide new insights into the treatment of CNS injury and neurodegenerative diseases in IAE.

Sex Differences in Case Fatality Rate of Patients With Severe Fever With Thrombocytopenia Syndrome.

Background: Severe fever with thrombocytopenia syndrome (SFTS) is a tick-borne disease with high mortality. However, detailed analysis is lacking to explore the complex effect of sex with age or comorbidities. Methods: A retrospective cohort study was performed among 2,938 SFTS patients entered during 2011-2020 in Xinyang, China. The case fatality rate (CFR) was estimated for their association with sex, age, and comorbidities by an interactive way. The difference of immune response between sex was explored in an age dependent way. Results: An overall CFR of 15.3% (450/2,938) was obtained, which appeared to be higher in males than in females [17.7% vs. 13.6%, adjusted odds ratio (aOR) = 1.24; 95% CI, 1.00-1.53; P = 0.048] and increased dramatically with age (P < 0.001). The associations between sex and SFTS fatal outcome were age-dependent and varied according to the status of comorbidities. The mortality-related risk conferred by older age was more pronounced in males, with aOR (95% CI) to be 5.76 (3.75-8.84) vs. 5.30 (3.54-7.95) in female. Sex-stratified analysis disclosed significant associations between death and comorbidities among female patients (aOR = 1.87, 95% CI: 1.40-2.49; P < 0.001), while none among males. Among females, the significant associations between presence of comorbidity and fatal outcome differed among age groups, with aOR (95% CI) decreased from 2.28 (1.16-4.46) in ≤60 years, to 2.06 (1.34-3.18) in 60-70 years and further to 1.55 (0.97-2.47) in >70 years. Altogether 194 SFTS patients were randomly selected for the test of B cells, natural killer (NK) cells, CD4 cells percentages, and anti-SFTSV IgM antibody level, the results revealed that males >60 years had significantly decreased percentages of B cells, CD4 cells, lower anti-SFTSV IgM antibody titer, and increased level of NK cells than male aged ≤60 years, while none of these age specific differences was observed in the females. This finding underlies the more pronounced age specific difference in CFR among male than female. Conclusions: Males had a significantly higher mortality of SFTS than did females, and more likely to be affected by aging for SFTS mortality. This difference can be explained by the effect from comorbidities and the host immunity. It is essential to take a sex- and age-based approach to SFTS treatment and management.