Using physical barriers to reduce the spread of respiratory viruses
Authors: Martin Dawes
Journal: BMJ (2007)

Preparing health professionals and the public for a flu pandemic has been the subject of much research worldwide, and governments and public health departments have published various recommendations over the past five years.1,2,3,4 One aspect of the clinical management of respiratory viruses—namely barrier methods to reduce transmission—is assessed in the accompanying systematic review by Jefferson and colleagues.5 This review found that handwashing and wearing masks, gloves, and gowns were effective individually in preventing the spread of severe acute respiratory syndrome, and even more effective when combined (odds ratio 0.09, 95% confidence interval 0.02 to 0.35, number needed to treat (NNT)=3, 2.66 to 4.97). The incremental effect of adding virucidals or antiseptics to normal handwashing to reduce respiratory disease was uncertain.

Because pandemic flu is such a potentially catastrophic event, governments worldwide should have commissioned such a review many years ago and not have left it to the academic community to take the lead. The academic community needs to educate governments that expert advice is not necessarily the best advice. Guidelines should be based on rigorous systematic reviews and need to be continuously updated.

Government and international websites such as the World Health Organization website on the status of pandemic flu (www.who.int/csr/disease/avian_influenza/phase/en/index.html) are of some help in keeping health professionals up to date with the latest information. However, regularly updated evidence based guidelines containing levels of recommendation and, where possible, measures of effectiveness such as NNT would be very much more helpful to front line clinicians. Guidelines also highlight where the strength of the evidence is weak and more research is needed. We have an annually updated guideline on the management of hypertension,6 and it reflects badly on the consistency of knowledge translation that one is not available for influenza.

The messages distributed by governments about how to reduce the spread of respiratory viruses have not been shown to be wrong, although some are not supported by evidence. Jefferson and colleagues’ review will allow the effectiveness of the interventions and the strength of the evidence supporting them to be much more explicit; for example, it will be possible to add numbers needed to treat for handwashing, face masks, and gloves to advisory leaflets for health professionals.

So how does the review help clinicians in primary care? The benefit of washing hands between patients is clear (NNT=4), as is wearing masks (NNT=6), wearing gloves (NNT=5), and wearing gowns (NNT=5). So practices need to have a stock of gloves, simple masks (not necessarily of the advanced N95 make), and gowns. Applying all the recommendations described by various government guidelines7—such as isolation, segregation, transport, and identification of patients, creating emergency telephone lists of staff, and on-call cover when staff are sick—may seem daunting to a small practice or office. However, the one advantage with influenza, compared with more sporadic epidemics such as pertussis, is that the practice plan can be tried, evaluated, and modified each year. 

Jefferson and colleagues point out that the quality of the trials was highly variable. We do not have enough evidence to be certain about many aspects of care for patients with suspected influenza—for example, which face mask is more cost effective within different healthcare settings. Although 336 trials on influenza have been registered on the WHO international clinical trials registry, only three trials are about reducing transmission using distancing (keeping a physical distance from patients with suspected disease) or barrier methods. The reasons for this include the lack of research capacity and funding and an emphasis on non-drug based treatments. Governments should continue to fund research to confirm the findings of this review and to investigate other areas of uncertainty that it identifies in the management of people with suspected influenza.