Epidemiology of influenza under the coronavirus disease 2019 pandemic in Nanjing, China

Monitoring School Absenteeism for Influenza-Like Illness Surveillance: Systematic Review and Meta-analysis

Background

Influenza causes considerable disease burden each year, particularly in children. Monitoring school absenteeism has long been proposed as a surveillance tool of influenza activity in the community, but the practice of school absenteeism could be varying, and the potential of such usage remains unclear.

Objective

The aim of this paper is to determine the potential of monitoring school absenteeism as a surveillance tool of influenza.

Methods

We conducted a systematic review of the published literature on the relationship between school absenteeism and influenza activity in the community. We categorized the types of school absenteeism and influenza activity in the community to determine the correlation between these data streams. We also extracted this correlation with different lags in community surveillance to determine the potential of using school absenteeism as a leading indicator of influenza activity.

Results

Among the 35 identified studies, 22 (63%), 12 (34%), and 8 (23%) studies monitored all-cause, illness-specific, and influenza-like illness (ILI)–specific absents, respectively, and 16 (46%) used quantitative approaches and provided 33 estimates on the temporal correlation between school absenteeism and influenza activity in the community. The pooled estimate of correlation between school absenteeism and community surveillance without lag, with 1-week lag, and with 2-week lag were 0.44 (95% CI 0.34, 0.53), 0.29 (95% CI 0.15, 0.42), and 0.21 (95% CI 0.11, 0.31), respectively. The correlation between influenza activity in the community and ILI-specific absenteeism was higher than that between influenza activity in community all-cause absenteeism. Among the 19 studies that used qualitative approaches, 15 (79%) concluded that school absenteeism was in concordance with, coincided with, or was associated with community surveillance. Of the 35 identified studies, only 6 (17%) attempted to predict influenza activity in the community from school absenteeism surveillance.

Conclusions

There was a moderate correlation between school absenteeism and influenza activity in the community. The smaller correlation between school absenteeism and community surveillance with lag, compared to without lag, suggested that careful application was required to use school absenteeism as a leading indicator of influenza epidemics. ILI-specific absenteeism could monitor influenza activity more closely, but the required resource or school participation willingness may require careful consideration to weight against the associated costs. Further development is required to use and optimize the use of school absenteeism to predict influenza activity. In particular, the potential of using more advanced statistical models and validation of the predictions should be explored.

Influenza vaccination features revealed by a single-cell transcriptome atlas

Emerging and re-emerging viruses like influenza virus pose a continuous global public health threat. Vaccines are one of the most effective public health strategies for controlling infectious diseases. However, little is known about the immunological features of vaccination at the single-cell resolution, including for influenza vaccination. Here, we report the single-cell transcriptome atlas of longitudinally collected peripheral blood mononuclear cells (PBMCs) in individuals immunized with an inactivated influenza vaccine. Overall, vaccination with the influenza vaccine only had a small impact on the composition of peripheral immune cells, but elicited global transcriptional changes in multiple immune cell subsets. In plasma and B cell subsets, transcriptomic changes, which were mostly involved in antibody production as well as B cell activation and differentiation, were observed after influenza vaccinations. In influenza-vaccinated individuals, we found a reduction in multiple biological processes (e.g., interferon response, inflammatory response, HLA-I/II molecules, cellular apoptosis, migration, and cytotoxicity, etc.,) 7 days postvaccination in multiple immune cell subsets. However, 14 days postvaccination, these levels returned to similar levels observed in prevaccination samples. Additionally, we did not observe significant upregulation of pro-inflammatory response genes and key thrombosis-related genes in influenza-vaccinated individuals. Taken together, we report a cell atlas of the peripheral immune response to influenza vaccination and provide a resource for understanding the immunological response mechanisms of influenza vaccination.

Sensitive and Rapid Diagnosis of Respiratory Virus Coinfection Using a Microfluidic Chip-Powered CRISPR/Cas12a System

The ongoing pandemic caused by severe acute respiratory syndrome coronavirus 2 is profoundly influencing the global healthcare system and people's daily lives. The high resource consumption of coronavirus disease 2019 (COVID-19) is resulting in insufficient surveillance of coinfection or resurgence of other critical respiratory epidemics, which is of public concern. To facilitate evaluation of the current coinfection situation, a microfluidic system (MAPnavi) is developed for the rapid (<40 min) and sensitive diagnosis of multiple respiratory viruses from swab samples in a fully sealed and automated manner, in which a nested-recombinase polymerase amplification and the CRISPR-based amplification system is first proposed to ensure the sensitivity and specificity. This novel system has a remarkably low limit of detection (50-200 copies mL^-1 ) and is successfully applied to detect 171 clinical samples (98.5% positive predictive agreement; 100% negative predictive agreement), and the results identify 45.6% coinfection among clinical samples from patients with COVID-19. This approach has the potential to shift diagnostic and surveillance efforts from targeted testing for a high-priority virus to comprehensive testing of multiple virus sets and to greatly benefit the implementation of decentralized testing.

From COVID-19 to Influenza-Real-Life Clinical Practice in a Pediatric Hospital

The COVID-19 pandemic, through the restrictions and the non-pharmaceutical interventions implemented, has importantly impacted the circulation and epidemiology of respiratory viruses. Specifically, the 2020/21 season was entirely dominated by SARS-CoV-2, while influenza activity reached an all-time low, despite initial warnings that a double concurrent epidemic could be possible. The current season, 2021/22, started with the shift of circulating SARS-CoV-2 variants from delta to omicron, which then rapidly spread globally, as most countries, including Romania, removed all restrictions and compulsory non-pharmaceutical interventions. In this report we present the clinical reality observed in March 2022 in a tertiary paediatric hospital in Bucharest, Romania, where we observed a sudden surge in influenza cases, after two consecutive years (March 2020 to March 2022) when influenza had stopped circulating in our country. Thus, in March 2022 the positivity rate of rapid influenza antigen tests unexpectedly increased to 33.5%, paralleled by a decrease to 7.5% in the positivity rate of rapid SARS-CoV-2 antigen tests. This significant increase in the influenza attack rate was observed from the first week (14.9% positivity rate), through the fourth week of March (42.1% positivity rate, p < 0.001), while the COVID-19 attack rate displayed a significant decreasing trend (from 11.2% to 4.8%, p < 0.001). These data serve as a warning about relaxing restrictions in a precipitous approach with minimised vigilance. The evolution of these observations needs to be followed very carefully in all countries, particularly in settings where epidemiological interactions and non-pharmaceutical interventions have so far led to the extensive circulation of only one of these viruses, and we should now be prepared to perform a correct differential diagnosis between influenza and COVID-19, in order to ensure the best quality of care and personalized management of each case of respiratory infection. The results of active influenza surveillance studies for the whole 2021/22 season are awaited, in order to quantify the joint influenza—COVID-19 burden among children.