Nonpharmaceutical interventions (NPIs) are in the news again. Yesterday was the dust up over Howard Markel and colleagues’ JAMA article from last August that appeared in CIDRAP News calling into question some of the historical data on the effectiveness of isolation and quarantine and now it’s an article in British Medical Journal that purports to show that some kinds of physical interventions like masks, gowns and handwashing might be better bets than vaccines and antivirals should a pandemic come our way:
Face masks and regular hand-washing are more likely to halt the spread of a deadly flu than all the antiviral drugs stockpiled worldwide, Australian experts say.
A global review has concluded that simple physical barriers will be more effective than drugs to prevent a pandemic of bird flu or another virulent bug.
The researchers from Australia, Italy, the US and the UK warn that combining measures like hand-washing and rigorous use of masks, gloves and gowns could be the best, and indeed only, line of treatment. (The Age [Australia])
All of this might well be true, but this paper is a pretty weak reed to lean upon. It was a systematic literature review of various studies that tried to gauge the effectiveness of a variety of practices in preventing the spread of respiratory infection. SARS and Respiratory Syncytial Virus (RSV) figure prominently but not influenza. Moreover the pertinent literature is for the most part neither abundant nor of high quality. From the paper’s Discussion section:
In this systematic review we found that physical barriers such as handwashing, wearing a mask, and isolation of potentially infected patients were effective in preventing the spread of respiratory virus infections. It is not surprising that methods of the included studies were at risk of bias as these types of interventions are difficult to blind, are often set up hurriedly in emergency situations, and funding is less secure than for profit making interventions. Hasty design of interventions to minimise public health emergencies, particularly the six included case-control studies, is understandable but not when no randomisation (not even of clusters) was done in the several unhurried cohort and before and after studies, despite randomisation leading to minimal disruption to service delivery. Inadequate reporting often made interpretation of before and after studies difficult.
The settings of the studies, carried out over four decades, were heterogeneous, ranging from suburban schools to military barracks, intensive care units, paediatric wards in industrialised countries, slums in developing countries,w1 and day care centres for children with special needs. Few attempts were made to obtain socioeconomic diversity by, for example, involving several schools in the evaluations of one programme. We identified few studies from developing countries where the most burden lies and where cheap interventions are needed. Even in Israel, the decrease in acute respiratory tract infections subsequent to school closure may have been related to atypical features: the high proportion of children in the population (34%) and limited access to over the counter drugs, which together with the national universal comprehensive health insurance means that symptomatic treatment is generally prescribed by doctors.
Compliance with interventions–especially educational programmes–was a problem for several studies, despite the importance of such low cost interventions. Routine long term implementation of some would be problematic–particularly maintaining strict hygiene and barrier routines for long periods, probably only feasible in highly motivated environments such as hospitals without the threat of an epidemic. (Jefferson et al., BMJ)
I give the authors credit for trying to ferret out as much information as they could from an impoverished scientific base. I fear they have slightly oversold their findings, although I fully appreciate the notion that in this case no harm is likely to result. The indicated measures are probably prudent even if we don’t have good information to know they work.
But we should face the fact we don’t really know more squarely. The Conclusion in the Abstract probably reflects the actual findings more accurately than their other statements:
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.
Yes, prolonged use of these methods would be difficult, and yes, they could be useful in reducing spread. But I think we knew this. What they added is there is precious little in the scientific literature to substantiate it although some of it might be suggestive. Unfortunately the paper came out sounding much more definite than warranted. Sigh.