Secondary attack rates from asymptomatic and symptomatic influenza virus shedders in hospitals: Results from the TransFLUas influenza transmission study

Respiratory virus infections in symptomatic and asymptomatic children upon hospital admission: new insights

Objective

Describe and compare the prevalence of symptomatic and asymptomatic or recently resolved respiratory infections in hospitalized children.

Design

Cross-sectional study.

Setting

Three hospital primary-to-quaternary care pediatric healthcare system.

Patients

People less than 22 years old who underwent admission screening for respiratory viruses using a multitarget polymerase chain reaction (PCR) panel from August 2020 through April 2022.

Methods

The symptom status of each patient was recorded by the ordering provider. The prevalence of each virus was described comparing symptomatic and asymptomatic patients. Results for each virus were stratified by age group and trends were examined over time.

Results

Of the 32,812 eligible PCR panels collected, 12,965 (39.5%), 18,651 (56.8%), and 1,196 (3.6%) were obtained from patients who were symptomatic, asymptomatic, or had missing or unknown symptom status, respectively. Symptomatic patients were much more likely to test positive for a respiratory virus (67.3% vs 27.0%). The most common viruses detected in asymptomatic patients were rhinovirus/enterovirus (18.0%), SARS-CoV-2 (3.6%), and parainfluenza viruses (2.3%). The odds ratio of testing positive when symptomatic was significantly greater than unity for all viruses but varied by virus and age group. The proportion of positive tests for each virus was dynamic and changed with intermittent epidemics, or viral "waves."

Conclusions

More than one-quarter of children without respiratory symptoms admitted to a pediatric healthcare system had PCR-detectable respiratory viruses. Children with symptoms of a respiratory infection are nevertheless much more likely to have a respiratory virus detected by PCR.

Incidence of laboratory-confirmed influenza and RSV and associated presenteeism and absenteeism among healthcare personnel, Israel, influenza seasons 2016 to 2019

BackgroundHealthcare personnel (HCP) are at high risk for respiratory infections through occupational exposure to respiratory viruses.AimWe used data from a prospective influenza vaccine effectiveness study in HCP to quantify the incidence of acute respiratory infections (ARI) and their associated presenteeism and absenteeism.MethodsAt the start and end of each season, HCP at two Israeli hospitals provided serum to screen for antibodies to influenza virus using the haemagglutination inhibition assay. During the season, active monitoring for the development of ARI symptoms was conducted twice a week by RT-PCR testing of nasal swabs for influenza and respiratory syncytial virus (RSV). Workplace presenteeism and absenteeism were documented. We calculated incidences of influenza- and RSV-associated ARI and applied sampling weights to make estimates representative of the source population.ResultsThe median age of 2,505 participating HCP was 41 years, and 70% were female. Incidence was 9.1 per 100 person-seasons (95% CI: 5.8-14.2) for RT-PCR-confirmed influenza and 2.5 per 100 person-seasons (95% CI: 0.9-7.1) for RSV illness. Each season, 18-23% of unvaccinated and influenza-negative HCP seroconverted. The incidence of seroconversion or RT-PCR-confirmed influenza was 27.5 per 100 person-seasons (95% CI: 17.8-42.5). Work during illness occurred in 92% (95% CI: 91-93) of ARI episodes, absence from work in 38% (95% CI: 36-40).ConclusionInfluenza virus and RSV infections and associated presenteeism and absenteeism were common among HCP. Improving vaccination uptake among HCP, infection control, and encouraging sick HCP to stay home are important strategies to reduce ARI incidence and decrease the risk of in-hospital transmission.

The role of asymptomatic infections in influenza transmission: what do we really know

Before the COVID-19 pandemic, the role of asymptomatic influenza virus infections in influenza transmission was uncertain. However, the importance of asymptomatic infection with SARS-CoV-2 for onward transmission of COVID-19 has led experts to question whether the role of asymptomatic influenza virus infections in transmission had been underappreciated. We discuss the existing evidence on the frequency of asymptomatic influenza virus infections, the extent to which they contribute to infection transmission, and remaining knowledge gaps. We propose priority areas for further evaluation, study designs, and case definitions to address existing knowledge gaps.

Nosocomial influenza in a pediatric general ward: Effects of isolation and cohort placement of children with influenza

OBJECTIVE

Many studies have described nosocomial outbreaks of influenza in specialized wards. We evaluated nosocomial transmission of influenza in a pediatric general ward.

DESIGN

Retrospective observational study.

SETTING

Single secondary hospital.

PATIENTS

The study included 814 hospitalized children with influenza between September 2015 and August 2020.

METHODS

The medical records of the included children were retrospectively reviewed, and clinical characteristics of children with community-acquired (CA) influenza and hospital-acquired (HA) influenza were determined. The room of each included child during hospitalization was traced to identify the children exposed to them.

RESULTS

CA influenza and HA influenza were diagnosed in 789 (96.9%) and 25 (3.1%) children, respectively. Among children with CA influenza, 691 (87.6%) were isolated or place in a cohort on admission. In total, 98 children (12.4%) admitted to multibed rooms exposed 307 children with noninfluenza diseases to influenza during 772 patient days; 3 exposed children (1.0%) were diagnosed with HA influenza. Including these 3 children, 25 children (19 without definite in-hospital exposure to influenza and 3 exposed to other children with HA influenza) were diagnosed with HA influenza, and 11 (44.0%) exposed 31 children with noninfluenza diseases to influenza for 85 patient days. Also, 3 exposed children (9.7%) were diagnosed with HA influenza, a significantly higher rate than that for CA influenza (P = .005). The clinical characteristics were comparable between children with HA influenza and those with CA influenza.

CONCLUSIONS

Cohort placement of children with influenza in a pediatric general ward can be effective in controlling nosocomial transmission of influenza. However, control measures for children with HA influenza should be emphasized.

Consequences of asymmetric mutational pressure for the dynamic of linear B-cell epitopes repertoire of influenza a virus neuraminidase rearrangement

Full-length nucleotide sequences of avian influenza A virus neuraminidase coding region (20,631 sequences) were analyzed and compared with those isolated from viruses infecting human and swine (63,750 sequences). If in fourfold degenerate sites there is asymmetric A-bias that may be more or less asymmetric depending on the type of neuraminidase and the host, than in twofold degenerate sites from third codon positions there is a strong asymmetric U-bias in coding regions of N4, N5, and N8 isolated from viruses infecting birds, as well as in those of N1 and N2 isolated from viruses infecting human, swine, and birds, while in coding regions of N9 isolated from birds, there is surprisingly strong C-bias, and in sequences of N3, N6, and N7 the usage of C is quite close to the level of U. Revealed stabilization of both U and C in twofold degenerate sites is the evidence of frequent changes in mutational pressure direction. Asymmetric mutational pressure was one of the sources of amino acid replacements that resulted in an equal percentage of sites with appeared and disappeared linear B-cell epitopes in N1, N2, N4, and N5 (33.62-35.33% vs. 32.41-36.45%, respectively), and controlled by the immune pressure it resulted in a stronger tendency to disappear for B-cell epitopes of N3, N6, N7, N8, and N9 of avian viruses (8.74-28.77% vs. 28.96-38.89%). The lack of correlation between nucleotide usages in fourfold and twofold degenerate sites for three nucleotides, except U, is a strong evidence of mutational pressure theory.

Droplet precautions on-site (DroPS) during the influenza season 2018/2019: a possible alternative to single room isolation for respiratory viral infections

Background

The guideline-driven and widely implemented single room isolation strategy for respiratory viral infections (RVI) such as influenza or respiratory syncytial virus (RSV) can lead to a shortage of available hospital beds. We discuss our experience with the introduction of droplet precautions on-site (DroPS) as a possible alternative.

Methods

During the 2018/19 influenza season we introduced DroPS on several wards of a single tertiary care center, while other wards maintained the traditional single room isolation strategy. On a daily basis, we evaluated patients for the development of respiratory symptoms and screened those with a clinical diagnosis of hospital-acquired respiratory viral infection (HARVI) for influenza/RSV by molecular rapid test. If negative, it was followed by a multiplex respiratory virus PCR. We report the concept of DroPS, the feasibility of the strategy and the rate of microbiologically confirmed HARVI with influenza or RSV infection on the DroPS wards compared to wards using the traditional single room isolation strategy.

Results

We evaluated all hospitalised patients at risk for a HARVI, 741 (72%) on the DroPS wards and 293 (28%) on the regular wards. The hospital-acquired infection rate with influenza or RSV was 2/741 (0.3%; 1× influenza A, 1× RSV) on the DroPS wards and 2/293 (0.7%; 2× influenza A) on the regular wards.

Conclusions

Droplet precautions on-site (DroPS) may be a simple and potentially resource-saving alternative to the standard single room isolation strategy for respiratory viral infections. Further studies in a larger clinical context are needed to document its safety.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13756-021-01038-y.

Attitudes of Healthcare Workers toward Influenza Vaccination in the COVID-19 Era

Healthcare workers (HCWs) are reluctant to participate in the influenza vaccination program, despite their high risk to contract and diffuse influenza due to professional exposure. The onset of the COVID-19 pandemic could raise HCW flu vaccination adherence. The aim of this study was to assess HCW attitudes toward influenza vaccination in the COVID-19 era. A multicenter observational study was carried out in three Italian hospitals (two in Pesaro and one in Fano, Marche region, Italy). Data about HCW influenza vaccination between 2013 and 2021 were extracted from the vaccination registers. An online questionnaire was sent to HCWs from July to October 2020 to assess their opinion about influenza vaccination in terms of knowledge, attitude, and practice during the COVID-19 pandemic. The number of flu-vaccinated HCWs increased from 3.7% in the 2013−2014 flu season to 53.6% in the 2020−2021 flu season (p < 0.001). About 15% (n = 324) of HCWs responded to the online questionnaire, and 30.5% of them declared that they had changed their minds on flu vaccination after the COVID-19 pandemic, deciding to get vaccinated. The COVID-19 pandemic significantly increased HCWs’ attitudes toward flu vaccination. However, flu vaccination adherence remained low and should be improved.

Influenza Vaccination Programs for Healthcare Personnel: Organizational Issues and Beyond

Healthcare personnel (HCP) are a high priority group for influenza vaccination aiming to protect them but also to protect vulnerable patients and healthcare services from healthcare-associated influenza and HCP absenteeism. Multi-component influenza vaccination programs targeting behavioral, organizational, and administrative barriers are critical, if influenza vaccination rates among HCP are to be raised on a sustained basis. Mandatory influenza vaccination policy is the only single intervention that can achieve high and sustainable vaccination rates in HCP in short term. In this article, we provide an overview of issues pertaining to influenza vaccination of HCP, with an emphasis on organizational issues of influenza vaccination programs.