Findings of a cluster randomized controlled trial of face masks and hand hygiene to prevent influenza transmission in households

Objective To systematically review evidence for the effectiveness of physical interventions to interrupt or reduce the spread of respiratory viruses. Data extraction Search trategy of the Cochrane Library, Medline, OldMedline, Embase, and CINAHL, without language restriction, for any intervention to prevent transmission of respiratory viruses (isolation, quarantine, social distancing, barriers, personal protection, and hygiene). Study designs were randomised trials, cohort studies, case-control studies, and controlled before and after studies. Data synthesis Of 2300 titles scanned 138 full papers were retrieved, including 49 papers of 51 studies. Study qualitywas poor for the three randomised controlled trials and most of the cluster randomised controlled trials; the observational studies were of mixed quality. Heterogeneity precluded meta-analysis of most data except that from six case-control studies. The highest quality clu ter randomised trials suggest that the spread of respiratory viruses into the community can be prevented by intervening with hygienic measures aimed at younger children. Meta-analysis of six case-control studies suggests that physical measures are highly effective in preventing the spread of SARS: handwashing more than 10 times daily (odds ratio 0.45, 95% confidence interval 0.36 to 0.57; number needed to treat=4, 95% confidence interval 3.65 to 5.52); wearing masks (0.32, 0.25 to 0.40; NNT=6, 4.54 8.03); weari g N95 masks (0.09, 0.03 to 0.30; NNT=3, 2.37 to 4.06); wearing gloves (0.43, 0.29 to 0.65; NNT=5, 4.15 to 15.41); wearing gowns (0.23, 0.14 to 0.37; NNT=5, 3.37 to 7.12); and handwashing, masks, gloves, and gowns combined (0.09, 0.02 to 0.35; NNT=3, 2.66 to 4.97). The incremental effect of adding virucidals or antiseptics to normal handwashing to decrease the spread of respiratory disease remains uncertain. The lack of proper evaluation of global measures such as screening at entry ports and social distancing prevent firm conclusions being drawn. Conclusion Routine long term implementation of some physical measures to interrupt or reduce the spread of respiratory virusesmight be difficult but many simple and low cost interventions could be useful in reducing the spread. INTRODUCTION Although respiratory viruses usually cause minor disease, epidemics can occur. Mathematical models estimate that about 36 000 deaths and 226 000 admissions to hospital in the United States annually are attributable to influenza, and with incidence rates as high as 50% during major epidemics worldwide, respiratory viruses strain health services, are responsible for excess deaths, 3 and result in massive indirect costs owing to absenteeism fromwork and school.Concern is now increasing about serious pandemic viral infections. In 2003 an epidemic of the previously unknown severe acute respiratory syndrome (SARS) caused by a coronavirus affected about 8000 people worldwide, with 780 deaths (disproportionately high numbers were in healthcare workers), and causing a social and economic crisis, especially in Asia. A new avian influenza pandemic caused by the H5N1 virus strain threatens greater catastrophe. High viral lo d and high v ral infectiousness probably drive virus pandemics, hence the need for interventions to reduce viral load. Mounting evidence suggests, however, that single measures, particularly the use of vaccines or antivirals, will be insufficient to interrupt the spread of influenza. Agent specific drugs are also not available for other viruses. A recent trial found handwashing to be effective in lowering the incidence of pneumonia in the developing world. Clear evidenc has also shown a link between personal (and environmental) hygiene and infection. We systematically reviewed the evidence for the effectiveness of combined public health measures such as personal hygiene, distancing, andbarriers to interrupt or reduce the spread of respiratory viruses. 13 We did not include vaccines and antivirals because these have been reviewed. 10 14-18 METHODS We considered trials (individual level, cluster randomised, or quasirandomised), observational studies (cohort and case-control), and any other comparative design in people of all ages provided some attempt had been made to control for confounding. We included any intervention to prevent the transmission of respiratory viruses from animals to humans Cochrane Vaccines Field, Alessandria, Italy Cochrane Wounds Group, Department of Health Sciences, University of York Faculty of Health Sciences and Medicine, Bond University, Gold Coast, 4229, Qld, Australia Cochrane Acute Respiratory Infections Group, Faculty of Health Sciences and Medicine, Bond University Public Health Agency of Lazio Region, Rome Department of Statistics, Manipal Academy of Higher Education, Manipal, India Correspondence to: C Del Mar cdelmar@bond.edu.au doi: 10.1136/bmj.39393.510347.BE BMJ | ONLINE FIRST | bmj.com page 1 of 9 on 27 January 2008 bmj.com Downloaded from Introduction Study design Results Discussion Hong Kong NPI RCT – Inclusion criteria Case-ascertainment design – index cases with influenza-like illness recruited from outpatient clinics • Any 2+ ILI symptoms or signs (broad definition). • Onset of symptoms within the last 48 hours. • Live with at least 2 other people. • No other household members have had ILIs within the past 2 weeks. BJ Cowling Hong Kong NPI study Slide 4 Introduction Study design Results Discussion NPI RCT – Study design