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

[Giuseppe]

Physical interventions to interrupt or reduce the spread of respiratory viruses: systematic review (BMJ, abstract, edited)

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

Tom Jefferson, researcher,1 Chris Del Mar, dean,2 Liz Dooley, managing editor, Cochrane Acute Respiratory Infections Group,2 Eliana Ferroni, researcher,1 Lubna A Al-Ansary, Shaikh Abdullah S Bahamdan research chair,4 Ghada A Bawazeer, researcher,5 Mieke L van Driel, professor of general practice ,2,3 Ruth Foxlee, information specialist,6 Alessandro Rivetti, information specialist7

1Acute Respiratory Infections Group, Cochrane Collaboration, Rome, Italy
2Faculty of Health Sciences and Medicine, Bond University, Gold Coast, Australia
3Department of General Practice and Primary Health Care, Ghent University, Belgium
4Department of Family and Community Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia
5Department of Clinical Pharmacy and King Khalid University Hospital, King Saud University, Riyadh, Saudi Arabia
6Department of Health Sciences, University of York, York
7Cochrane Vaccines Field, Azienda Sanitaria Locale, Alessandria, Italy

Correspondence to: T Jefferson, Cochrane Acute Respiratory Infections Group, 00061 Anguillara Sabazia, Rome, Italy
jefferson.tom@gmail.com

Cite this as: BMJ 2009;339:b3675 - doi:10.1136/bmj.b3675


ABSTRACT

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

Data sources
Cochrane Library, Medline, OldMedline, Embase, and CINAHL, without restrictions on language or publication.

Data selection
Studies of any intervention to prevent the transmission of respiratory viruses (isolation, quarantine, social distancing, barriers, personal protection, and hygiene). A search of study designs included randomised trials, cohort, case-control, crossover, before and after, and time series studies. After scanning of the titles, abstracts and full text articles as a first filter, a standardised form was used to assess the eligibility of the remainder. Risk of bias of randomised studies was assessed for generation of the allocation sequence, allocation concealment, blinding, and follow-up. Nonrandomised studies were assessed for the presence of potential confounders and classified as being at low, medium, or high risk of bias.

Data synthesis
58 papers of 59 studies were included. The quality of the studies was poor for all four randomised controlled trials and most cluster randomised controlled trials; the observational studies were of mixed quality. Meta-analysis of six case-control studies suggested that physical measures are highly effective in preventing the spread of severe acute respiratory syndrome: 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 combination was also effective in interrupting the spread of influenza within households. The highest quality cluster randomised trials suggested that spread of respiratory viruses can be prevented by hygienic measures in younger children and within households. Evidence that the more uncomfortable and expensive N95 masks were superior to simple surgical masks was limited, but they caused skin irritation. The incremental effect of adding virucidals or antiseptics to normal handwashing to reduce respiratory disease remains uncertain. Global measures, such as screening at entry ports, were not properly evaluated. Evidence was limited for social distancing being effective, especially if related to risk of exposure?that is, the higher the risk the longer the distancing period.

Conclusion
Routine long term implementation of some of the measures to interrupt or reduce the spread of respiratory viruses might be difficult. However, many simple and low cost interventions reduce the transmission of epidemic respiratory viruses. More resources should be invested into studying which physical interventions are the most effective, flexible, and cost effective means of minimising the impact of acute respiratory tract infections.

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[Sally Furniss]

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

Cheap physical interventions reduce spread of epidemic respiratory viruses

Last Updated: 2009-09-22 19:01:24 -0400 (Reuters Health)

NEW YORK (Reuters Health) - Low-cost measures, such as washing hands and wearing masks and gloves, can interrupt transmission of epidemic and pandemic acute viral respiratory tract infections, according to a systematic review published September 23 in BMJ Online First.

Yet public health recommendations continue to focus on antiviral agents and influenza-specific vaccines, "despite the lack of strong evidence," the authors point out. Moreover, vaccines only target a small proportion of illnesses, whereas physical interventions are directed against all viruses.

Data sources for review, which was headed by Dr. Tom Jefferson from the Cochrane Collaboration in Rome, included the Cochrane Library, Medline, Old Medline, Embase, and CINAHL. In 2007, Dr. Jefferson was the lead author of a Cochrane review on the same topic: "Interventions for the interruption or reduction of the spread of respiratory viruses." That review covered 51 studies; the current analysis covered 59 studies conducted over 4 decades, as described in 58 papers.

The studies compared physical interventions - isolation, quarantine, social distancing, barriers, personal protection, or hygiene - with no intervention or another intervention. Studies of vaccines and antivirals were not included.

"The highest quality cluster randomized trials indicate that the most effect on preventing the spread of respiratory viruses can be expected from hygienic measures in younger children and household members of index cases," Dr. Jefferson and his colleagues report.

A meta-analysis of 6 case-control studies showed that such measures are highly effective in preventing the spread of severe acute respiratory syndrome (SARS), the authors report. Washing hands more than 10 times a day was associated with an odds ratio for SARS transmission of 0.45. Other measures included wearing masks (OR 0.32), wearing N95 masks (OR 0.09), wearing gloves (OR 0.43), and wearing gowns (OR 0.23).

The combination of all 4 personal hygiene and barrier methods reduced risk by 91%, with a number needed to treat of 3.

A combination of handwashing, gloves, masks and gowns was also effective at interrupting the spread of influenza within households.

Dr. Jefferson's group advises that because gloves and N95 masks can cause acne, itch, rash and dry skin, such measures should be reserved for high-threat situations, particularly in hospitals. The team also recommends that "society should invest in more comfortable and better designed face masks and barrier apparatus, which would increase compliance with their use."

The authors call for further research to find the most effective, flexible and cost-effective measures. "Cheap and non-invasive interventions," they write, "have the potential to reduce mortality and morbidity from viral respiratory tract infections."

BMJ 2009;339:b3675.

http://www.rtmagazine.com/reuters_article.asp?id=20090922publ001.html