Photo Credit – CDC
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As was well illustrated during the opening months of the 2009 H1N1 pandemic – until a vaccine can be developed, produced, and distributed – public health interventions to reduce the spread of a virus are fairly limited, and consist primarily of NPIs – or Non-Pharmaceutical Interventions.
Credit CDC Non-Pharmaceutical Interventions
The goal, in those early months before a vaccine becomes available, is to reduce the spread of the virus as much as possible. In this way, the burden on health care facilities, and toll of absenteeism and on the lives of those effected can be reduced.
Source - Community Strategy for Pandemic Influenza Mitigation
NPI’s have been described as being like slices of Swiss cheese, with each containing large holes through which the virus can pass, but when stacked on top of each other, can provide an effective barrier.
While it is known that these measures can help reduce influenza transmission, there are many open questions regarding their relative merits, cost effectiveness, and optimum combination.
Among the researchers trying to nail down these merits, is Dr. Allison Aiello whose work at the University of Michigan we’ve examined previously. Back in 2010, in Michigan NPI Study: A Closer Look and Study: Effectiveness of NPIs Against ILI's, we looked at a multi-year research project that compared the effectiveness of handwashing and facemasks (alone, and in combination) at reducing the spread of seasonal influenza in a college dorm setting.
Their results?
Neither face mask use and hand hygiene nor face mask use alone was associated with a significant reduction in the rate of ILI, although combined, they produced a 35% to 51% reduction of infection over the control group.
Although this study did not directly study the effectiveness of hand washing alone, the implication here is that alcohol sanitizers and hand washing alone may not be as protective as has been hoped in the past.
Flash forward four years and Dr. Aiello (now Professor of Epidemiology at UNC) is back with a study (along with Dr. Benjamin Cowling and V. W. Y. Wong of the University of Hong Kong) that looked at earlier studies in order to evaluate the effectiveness of hand hygiene alone in preventing influenza infection.
V. W. Y. WONGa1, B. J. COWLINGa2 c1 and A. E. AIELLOa3
SUMMARY
Community-based prevention strategies for seasonal and pandemic influenza are essential to minimize their potential threat to public health. Our aim was to evaluate the efficacy of hand hygiene interventions in reducing influenza transmission in the community and to investigate the possible modifying effects of latitude, temperature and humidity on hand hygiene efficacy. We identified 979 articles in the initial search and 10 randomized controlled trials met our inclusion criteria.
The combination of hand hygiene with facemasks was found to have statistically significant efficacy against laboratory-confirmed influenza while hand hygiene alone did not. Our meta-regression model did not identify statistically significant effects of latitude, temperature or humidity on the efficacy of hand hygiene.
Our findings highlight the potential importance of interventions that protect against multiple modes of influenza transmission, and the modest efficacy of hand hygiene suggests that additional measures besides hand hygiene may also be important to control influenza.
Before proceeding, I would note that the advice from the CDC, HHS, WHO and just about every other public health agency around to globe to `wash your hands often’ is undoubtedly sage counsel, and can protect you against a wide range of illnesses and disease.
I am, and will continue to be, an inveterate hand washer and you are unlikely to find me out and about without a bottle of alcohol hand-sanitizer within reach.
But as far as influenza (and other common ILIs) are concerned, there isn’t a lot of evidence that handwashing alone offers much of a protection against infection. Something I wrote about at some length back in 2009 (see Sanitized For Your Protection and The Flaw In The Ointment).
While it is true that some influenza infections undoubtedly come via fomites (contaminated surfaces which we touch and then transfer to our mouths, eyes, or nose) - and that hand-washing might prevent some of those - most researchers would grant that most influenza is probably transmitted through large droplet or aerosol routes.
Which would explain why studies have shown that combining handwashing with respiratory protection does appear to provide a significant degree of protection against influenza-like illnesses.
The problem with facemasks and other forms of PPEs (Personal Protective Equipment)– particularly during a severe pandemic – is one of supply.
Our Strategic National Stockpile contains more than 100 million N95 and surgical masks (see Caught With Our Masks Down), but the demand for PPEs during a serious pandemic would far exceed the supply.
At one time the HHS estimated the nation would need 30 billion masks (27 billion surgical, 5 Billion N95) to deal with a major pandemic (see Time Magazine A New Pandemic Fear: A Shortage of Surgical Masks).
Making it difficult for the CDC, WHO, and other public agencies to broadly recommend their use, knowing they would quickly be in short supply.
Still, the CDC has in the past suggested that individuals and businesses may wish to stockpile a small quantity of facemasks (see Minnesota Health Department May 2007: Volume 2, Number 5 (PDF: 127KB/4 pages) as part of their general pandemic preparedness.
CDC officials could not emphasize enough that masks alone will not be sufficient to eliminate the risk of infection during a pandemic. Facemasks (e.g., surgical masks) and respirators (e.g., N95 masks) should be used in combination with other preventive measures, such as hand hygiene and social distancing, to help reduce the risk for influenza infection during a pandemic.
Respirators (e.g., N95 masks) are still only being recommended for individuals who have unavoidable close contact with infected persons. Whenever possible, rather than relying on the use of facemasks (e.g., surgical masks) and respirators (e.g., N95 masks), close contact and crowded conditions should be avoided during an influenza pandemic. Facemasks (e.g., surgical masks) should be considered for use by individuals who enter crowded settings, both to protect their nose and mouth from other people’s coughs and to reduce the wearers’ likelihood of coughing on others. The time spent in crowded settings should be as short as possible.
Last July, in The Great Mask Debate Revisited I wrote about the pros and cons regarding facemasks, and the various studies comparing the protective qualities of surgical masks vs. N95 masks.
Neither type should be regarded as perfect protection against infection, and with regards to the more expensive N95s, it takes more than just having a box in your closet (see Survival Of The Fit-tested) to protect you.
The bottom line, is that you hope to avail yourself of the (admittedly, limited) protection afforded by facemasks during a pandemic, your best bet is to buy any supplies well before a pandemic erupts.
As far as the `wash your hands’ meme is concerned, while perhaps oversold for preventing influenza infection, hand washing is simple, cost effective, and has proven benefits as part of basic disease prevention and hygiene.
Which makes it an important component in any public health strategy, regardless of whether we find ourselves in the midst of an influenza epidemic.
