Proper filtration can help to minimize the risk of spreading the flu virus.
An outbreak of influenza A (H5N1) also known as “avian flu” or “bird flu” has been reported in countries throughout Asia. Confirmed human cases of avian flu have been found in Thailand, Vietnam and China. There have been approximately 150 human cases with a fatality rate of over 60%. No known cases have been reported of human to human spread of the disease. Just about every year there is some type of avian flu problem. However, the influenza A (H5N1) appears to be particularly troubling because of its high fatality rate. Those with asthma and other respiratory diseases would be particularly vulnerable.
Many experts predict that it is just a matter of time before the virus mutates into a form that can be transferred human to human. Health agencies all over the world have been preparing for this contingency. What special filtration precautions should be taken in case of an avian flu outbreak?
First, the avian flu virus ranges in size from 0.08 to 0.13 micrometers (microns) in diameter. In human to human contact they would be carried in respiratory secretions as small-particle aerosols ( 5 to 10 micrometers in diameter). Particles in this size range settle out of the air fairly quickly so the greatest danger would be within 3 feet of the infected person. Wearing a mask with at least an N95 rating would be necessary for anyone coming into close contact with someone infected with influenza A (H5N1). It is also advisable that anyone suspected of having the virus wear a mask as well. As with any virus the first line of defense would be frequent hand washing.
A patient with avian flu in any health care facility should be kept in an airborne isolation room with negative air pressure in relation to the surrounding areas with 6 to 12 air exchanges per hour. The HEPA air filters used in an airborne isolation room would be effective in stopping the airborne spread of the virus. If an airborne isolation room is not available, then a stand alone HEPA air purifier could be used with a minimum of 6 air exchanges per hour.
In a recirculating HVAC system in a home, office or other facility at least a MERV 11 filter should be used. This would capture a minimum of 95% of particles 5 micrometers in size or larger.