Warding Off H5N1

A new breed of antimicrobial respirators is designed to defend against biological pathogens.

Very few individuals, families, companies, hospitals, cities, or even countries are properly prepared to prevent or minimize the human morbidity and mortality, the social disruption, and the economic consequences caused by the results of an H5N1 avian influenza pandemic.

Influenza pandemic (or global epidemic) could occur if a new influenza virus subtype appears against which no person on earth is likely to be immune. It is possible that avian influenza could result in several simultaneous epidemics worldwide with high numbers of infection cases and many deaths. With the increase in global air travel and urbanization, a pandemic caused by the H5N1 bird flu virus may occur rapidly around the world.

Global pandemics have been reported for many hundreds of years. The best-documented pandemics occurred in 1918 (H1N1, the Spanish flu), in 1957 (H2N2, the Asian flu), and 1968 (H3N2, the Hong Kong flu). The consequences of another influenza pandemic are likely to include millions of deaths, tremendous social disruption, and profound economic losses worldwide. Experts predict economic losses to be in the many trillions of dollars.

Influenza experts agree another pandemic is likely to happen but are unable to say when. In the more conservative scenarios, it has been calculated that the world will face up to 233 million outpatient visits, 5.2 million hospital admissions, and 7.4 million deaths globally within a very short period, should the H5N1 virus mutate to transmit from human to human. Thus far, the virus has been spread from bird to human through direct contact with infected birds and possibly other animals, such as cats and dogs.

Preventive Measures
A vaccine for H5N1 avian influenza is not yet available and may never be available. Even if a vaccine were to be developed, it still must be produced in mass quantities, and that will take a prolonged production period. It should also be noted that viruses mutate rapidly, therefore, a vaccine based on an early genetic version of a virus may not protect against the latest mutation.

Most experts will advise that traditional methods of attentive washing of hands and disinfecting surfaces are good methods to reduce the chance of infection from any virus. Using sound hand and respiratory hygiene are the best-known defenses.

Use of face masks and respirators will be key in the event of a H5N1 outbreak. What is the difference between a face mask and a respirator? These terms are often used interchangeably, but there is a big difference. Air must pass through respirators, such as N95 respirators, whereas when using a simple face mask, such as a procedural mask or a surgical mask, air also may be breathed in from the "leaky" sides. Face masks offer little viral protection when compared to respirators.

It is critical that if/when the H5N1 influenza pandemic occurs, people wear respirators to protect themselves from respiratory secretions of other persons who may be infected. Another important reason to use respirators is to reduce the spreading of secretions from coughing and sneezing from an affected person to prevent contaminating others. Infected people should wear respirators to protect people who are not yet infected.

More Effective Respirator Technologies
What are the common types of protective respirators? The Centers for Disease Control, World Health Organization, and National Institute for Occupational Safety and Health suggest people use an N95 respirator that has 95 percent efficiency in filtering out particles greater than 0.3 micron under normal rate of respiration. N95s were created to protect workers from industrial dust and particulates.

While commercially available N95 respirators filter out most dust particles, bacteria, and fungi, viruses fall below the 0.3 micron size and can escape filtration. Because NIOSH-approved N95s respirators have traditionally been effective in TB control, they have been recommended by CDC and WHO for other biological particles, such as SARS and avian influenza. However, the NIOSH certification process does not include an evaluation of viral filtration efficiency. Furthermore, recent studies suggest that NIOSH-approved respirators do not exclude biological particles less than 0.3 microns in size with 95 percent filtration efficiency as was historically assumed.

Another important factor is that respirators vary in their ability to remove viruses passing through them from the air stream passing through and have a limited length of time they can maintain a given filtration efficiency. Traditional N95 respirators are not as effective as new-generation respirators that use antimicrobial properties. N95s have limitations. Most of the infectious viruses are smaller than the maximum filtering capacity of these masks. Moreover, the mask only traps filtered products without neutralizing the virulence of the infectious particle.

Federal guidelines for pandemic preparedness suggest the use of standard NIOSH-approved N95 disposable respirators. While commercially available N95 disposable respirators are effective at filtering out particulate matter and most bacteria, they are not designed for viruses that are significantly smaller.

Recognizing the need for better protection against airborne viruses in the face of emerging pathogens, pandemic threats, and the possibility of biological attacks, a new breed of antimicrobial respirators is designed to defend against biological pathogens. One brand uses a unique iodine preparation that harnesses the antimicrobial power of iodine. This respirator controls the delivery and dosage of molecular iodine directly to microorganisms. Other technologies include nanotechnology-enhanced filter media to effectively isolate and destroy viral and bacterial contaminants.

With the ominous threat of avian influenza looming, respirator manufacturers are growing more determined to employ high-tech solutions that can provide real protection against airborne viral threats. Stay tuned for more developments.

This article originally appeared in the October 2007 issue of Occupational Health & Safety.

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