Man-Bear-Pig Flu and Masks

When an event occurs that raises the awareness of the general population to a risk from a particular threat, the mitigation strategy of many individuals seems to entail taking actions that do not in fact address the threat. Instead they purchase equipment and take actions that only make them feel better with out in fact lowering their risk at all.

Take for example the recent run on filter masks in response to the spread of swine flu (or as I have taken to calling it man-bear-pig flu). There are several different kinds of masks, you’ve probably seen and maybe even used one at some point in your life.

I’ve been wondering what kinds of mask will protect against an airborne virus. Some masks are designed to protect against gases and vapors. Others are designed to protect against dust, ash and other particulates. Given the wide range and variety in masks I set about finding out which would help against man-bear-pig flu.

You can download a pdf explaining the differences between different kinds of mask ratings from the Agriculture and Agra-Food Canada here.

The following quote comes from this PDF:

Do N95 respirators provide 95% protection level against airborne viruses, and how adequate are surgical masks?

The 95 in N95 indicates that the mask is supposed to provide 95% “filter efficiency” for 300nm particles.

Background: Respiratory protection devices are used to protect the wearers from inhaling particles suspended in the air. Filtering face piece respirators are usually tested utilizing nonbiologic particles, whereas their use often aims at reducing exposure to biologic aerosols, including infectious agents such as viruses and bacteria.

Methods: The performance of 2 types of N95 half-mask, filtering face piece respirators and 2 types of surgical masks were determined. The collection efficiency of these respiratory protection devices was investigated using MS2 virus (a nonharmful simulant of several pathogens). The virions were detected in the particle size range of 10 to 80 nm.

Results: The results indicate that the penetration of virions through the National Institute for Occupational Safety and Health (NIOSH)-certified N95 respirators can exceed an expected level of 5%. As anticipated, the tested surgical masks showed a much higher particle penetration because they are known to be less efficient than the N95 respirators. The 2 surgical masks, which originated from the same manufacturer, showed tremendously different penetration levels of the MS2 virions: 20.5% and 84.5%, respectively, at an inhalation flow rate of 85 L/min.

Conclusion: The N95 filtering face piece respirators may not provide the expected protection level against small virions. Some surgical masks may let a significant fraction of airborne viruses penetrate through their filters, providing very low protection against aerosolized infectious agents in the size range of 10 to 80 nm. It should be noted that the surgical masks are primarily designed to protect the environment from the wearer, whereas the respirators are supposed to protect the wearer from the environment.

Here is an image of a surgical mask:

And here is an image of an N95 mask:

Reiterating from the conclusion about the N95 masks above, It should be noted that the surgical masks are primarily designed to protect the environment from the wearer, whereas the respirators are supposed to protect the wearer from the environment.

Taking a look at the expanded conclusions:

CONCLUSIONS
Two types of N95 half-mask respirators and 2 types of surgical masks were challenged with aerosolized MS2 virus. The experiments were carried out following a manikin-based protocol. The results indicate that N95-certified respirators may not necessarily provide a proper protection against virus, which is considerably smaller than the accepted most penetrating particle size of 300 nm used in the certification tests. Thus, the protection against the airborne viral agents provided by some N95 respirators may fall below 95%, especially at higher inhalation flow rates. The efficiency of the surgical masks is much lower than that of the N95 respirators so that the MS2 virions penetrate readily through the surgical masks. The performance tests conducted with surgical masks challenged with latex spheres of ~300 nm or bacterial particles may underestimate the penetration of nanosize virions.

So, what it sounds like to me is that while a virus may in fact be smaller than 300nm, an N95 will provide some protection against the transmission of the virus, though not 95% efficiency. It will provide significantly better protection than a surgical mask.

My understanding is that influenza is not technically an airborne virus. It spreads via the droplets that come from spit/snot when someone who is infected sneezes or coughs. However, the virus can not apparently live long outside of the heat and moisture variables that allows it to thrive in a living body. Once the droplet cools or dries, the virus dies.

If that is indeed the case and we are trying to keep out human droplets then it sounds like an N95 mask will indeed lower your risk of being exposed to influenza.

As with other diseases some basic common-sense practices can help protect you from contracting the man-bear-pig flu.

• Limit contact with other humans.
• Wash your hands.
• Keep your hands out of your eyes/nose/mouth.
• Avoid touching objects that are touched often by other people. Door knobs, handles, cash, etc.

Threats aren’t to be feared. They are to be recognized, evaluated and mitigated.

The likelihood of their occurrence should be considered in an effort to evaluate your actual risk. Over the last few weeks the likelihood of contracting man-bear-pig flu has increased.

If it gets bad enough that we need to be wearing masks then it may be time to limit your exposure to other people. Having the appropriate resources (food and water) to sustain yourself is crucial to doing this. If you have to leave to find supplies you may very well end up infected and return home to spread the disease to your friends and family.

Taking calculated actions that mitigate your vulnerability to this particular threat will help to lower your risk.

The two most useful weapons in your toolbox at this moment may quite simply be basic hygiene and a common N95 particulate mask.