Efficacy of hand hygiene to reduce transmission of the influenza virusin community settings: a meta-analysis

Abstract

BACKGROUND Influenza is a potential threat to life, economies and security in our globalized world. However, it is still unclear how efficacious non-pharmaceutical interventions are in reducing the virus’ transmission and how the underlying mechanisms of its transmission modes work. Since 2008, numbers of randomized controlled trials (RCTs) regarding the efficacy of hand hygiene interventions in reducing influenza transmission have been published, yet no metaanalysis has ever been performed. Besides, a guinea pig model in 2009 showed that the efficiency of aerosol transmission is adjusted by the ambient temperature and humidity. Therefore, further evidence is needed to confirm the hypothesis.

OBJECTIVES To evaluate the efficacy of hand hygiene interventions alone or combined with facemasks in reducing influenza transmission in the community and to investigate the possible roles of latitude, temperature and humidity in relation to the efficacy of the interventions in controlling the spread of influenza.

SEARCH METHODS This meta-analysis followed the PRISMA statement. I searched the MEDLINE, PubMed, EMBASE, Cochrane Central Register of Controlled Trials and Cochrane Library databases.

SELECTION CRITERIA I included all RCTs assessing the effect of hand hygiene interventions in preventing influenza spread in community settings with clear outcome definitions of laboratory confirmed influenza, clinically diagnosed influenza-like illness (ILI) and their related absenteeism.

DATA COLLECTION AND ANALYSIS I ranked the methodological quality of each outcome with GRADEprofiler. I also assessed the heterogeneity across RCTs using I2 statistic and publication bias through visual inspection of Begg’s funnel plots and statistical assessment of regression and rank-correlation. I conducted the meta-analysis with random-effect models and further performed separate analyses for developed and developing countries data in case of a significant level of heterogeneity being noted across the studies. I also incorporated meta-regression to assess the association of latitude, temperature and humidity with the efficacy of hand hygiene interventions.

RESULTS I identified 1,593 articles in the initial database search, excluded 1,535, included five from reference lists of review articles, retrieved full articles of 33 and included ten for analysis. The quality of evidence of both laboratory confirmed influenza and ILI were high while that of absenteeism was low. The combination of hand hygiene interventions and facemasks contributed to a significant 45% reduced risk of influenza-related absenteeism in the combined country data while it contributed a significant 23% to a reduced risk of both laboratory confirmed influenza and ILI in developed countries subgroup analysis. The metaregression revealed that the efficacy of the combination of hand hygiene interventions with facemasks increased in a less humid environment.

CONCLUSIONS The combination of hand hygiene interventions with facemasks is an effective low-cost intervention to prevent influenza. Further studies to assess the association between humidity and mode of influenza transmission are critically important to support the international guideline on hand hygiene interventions and facemask use.