Tuesday, April 28, 2009

Swine Flu and Infection Risk

The emergence of a new influenza virus has created a frenzy of misinformation and panic. TV news shows people wearing paper face mask, the latest signal that the world is a dangerous place. While I have broadcast my concern for many years that infection surveillance is inadequate and promoted a new ethic of social responsibility, I find the frantic media reports this week to be offensive if not absurd. Social responsibility means -- don't spread infections you have acquired; if you are sick, stay at home.

There are real dangers in the world. Infectious agents evolve continuously. Increasing populations and increasing urban density are ideal for infection transmission. Transportation of people and goods all over the world means that infections become worldwide in a matter of days, not localized. I continue to meet physicians who think they are living in the nineteeth century and refer to localized, "endemic" infection.

Solutions can only be found by well-informed, calm methodical people. Turn off CNN and let us proceed with caution and appropriate concern. In my business, we have looked at air quality issues for several decades. Here is a response to a typical question we addressed:

Question: I do a lot of international flying, from North American to Asia, several times a month. I have gotten, many times, upper respiratory infections, bronchitis, bad coughs that my physicians, as well as my common sense, tells me comes a great deal from the poor air quality on airplanes. In addition, just the past week, with the outburst of some kind of Asian virus with serious symptoms, I want to protect myself as much as possible, while at least on the airplanes. What masks do you suggest, and any other comments or suggestions you might have?

Answer: We have looked at this problem repeatedly over 2 decades and not arrived at a satisfactory method of personal protection except for canceling the flight. You have to accept that traveling involves exposure to thousands of strangers who may infect you with microbes most of which, you have not encountered before and you will lack protective immunity. This increased exposure begins when you leave home and continues even after you arrive back.

You have to disinfect everything, including yourself, before you are free of foreign microbes. It’s easy to focus on the in-flight conditions, but exposure in the aircraft is only a small component of the overall risk of infection when you travel. Biological agents infect through the respiratory mucosa; ingestion; contact with the mucous membranes of the eyes, or nasal tissues; by penetration of the skin through scratches, small cuts and abrasions Organic airborne particles share the same characteristics in air or on surfaces as inorganic particles from hazardous dusts.

Here is a quick summary of the basic strategies you can use:

Disposable paper face masks provide minimal protection against dusts, fungal spores and bacteria, but not viruses. These are obviously the cheapest, most available and probably most acceptable to wear in public including in airports and perhaps on a flight. The protection rating is hard to assess, but is probably very low in the range of 5-10. Paper masks with a NIOSH protection rating of 100 offer better protection against viruses, if you wear them properly.

The mask has to be changed often and you must wash your hands after handling the mask. For more serious protection you can use half-mask or full-face air-purifying respirators with particulate filter efficiencies ranging from N95 (for hazards such as pulmonary tuberculosis) to P100 (for hazards such as viruses). The protection rating is somewhere between 50-200, depending on the filter chosen and degree of proper utilization.

The best protection against airborne infectious agents (as well as all airborne toxins) is provided by self-contained breathing apparatus (SCBA) respirators with a full facepiece operated in a positive pressure mode. This reduces the hazard from most sources -- airborne particles, microbes, chemical vapors and gases. The National Institute for Occupational Safety and Health (NIOSH) suggests that the proper use of SCBA reduces the user’s exposure by at least 10,000.

Decontamination of clothing is a precaution against particles that have settled on the outside. Use detergent, hot water, and 0.5% hypochlorite solution (one part household bleach to 10 parts water) to wash clothes and baggage. You should wash your hands frequently and shower ASAP after a flight using generous quantities of detergent and water. Shampoos contain detergents that tend to be better cleansers than regular soap. Use a basic shampoo as a whole body wash.

Until more people wear APRs and everyone is used to them, we can assume that if you strap one on to go to work, travel in an airplane or walk the dog, most people will think " you look weird!" We are not sure how new security regulations will treat the use of APRs on airplanes… it will controversial.

See the book, Air and Breathing by Stephen Gislason MD