Intended for healthcare professionals


Physical interventions to interrupt or reduce the spread of respiratory viruses: systematic review

BMJ 2008; 336 doi: (Published 10 January 2008) Cite this as: BMJ 2008;336:77
  1. Tom Jefferson, coordinator1,
  2. Ruth Foxlee, trials search coordinator2,
  3. Chris Del Mar, dean3,
  4. Liz Dooley, review group coordinator4,
  5. Eliana Ferroni, researcher5,
  6. Bill Hewak, medical student3,
  7. Adi Prabhala, medical student3,
  8. Sree Nair, professor of biostatistics6,
  9. Alex Rivetti, trials search coordinator1
  1. 1Cochrane Vaccines Field, Alessandria, Italy
  2. 2Cochrane Wounds Group, Department of Health Sciences, University of York
  3. 3Faculty of Health Sciences and Medicine, Bond University, Gold Coast, 4229, Qld, Australia
  4. 4Cochrane Acute Respiratory Infections Group, Faculty of Health Sciences and Medicine, Bond University
  5. 5Public Health Agency of Lazio Region, Rome
  6. 6Department of Statistics, Manipal Academy of Higher Education, Manipal, India
  1. Correspondence to: C Del Mar cdelmar{at}
  • Accepted 23 October 2007


Objective To systematically review evidence for the effectiveness of physical interventions to interrupt or reduce the spread of respiratory viruses.

Data extraction Search strategy 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 quality was 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 cluster 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 to 8.03); wearing 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 viruses might be difficult but many simple and low cost interventions could be useful in reducing the spread.


  • We thank Peter Doshi, Anne Lyddiatt, Stephanie Kondos, Tom Sandora, Kathryn Glass, Max Bulsara, and Allen Cheng for commenting on the draft protocol; Jørgen Lous for translating a Danish paper and extracting data; Taixiang Wu for translating Chinese text; and Ryuki Kassai for translating Japanese text.

  • Contributors: RF and AR constructed the search strategy. TJ, CDM, and LD drafted the protocol. LD, CDM, and RF incorporated the referees’ comments. TJ, FE, BH, and AP extracted study data. SN carried out the analyses. TJ and CDM wrote the final report and are the guarantors for the paper. All authors contributed to the final paper.

  • Funding: Cochrane Collaboration Steering Group, UK, and each author’s institution.

  • Competing interests: None declared.

  • Ethical approval: Not required.

  • Provenance and peer review: Not commissioned; externally peer reviewed.

  • Accepted 23 October 2007
View Full Text