FW: [occ-env-med-l] Flu Spread in temperate zones by aerosol, in tropics by contact: A hypothesis

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Dale,Personally I do not know but this might be a good "parallel question" for the IEQ List at http://health.groups.yahoo.com/group/iequality/Best wishes, Cutz Cutz, CIH | Moderator, GlobalOccHyg List | http://health.groups.yahoo.com/group/globalocchyg-list/FURTHER TO...Subject: RE: [occ-env-med-l] Flu Spread in temperate zones by aerosol, in tropics by contact: A hypothesisFrom: DWalsh@...To: andrewcutz@...; occ-env-med-l@...Date: Wed, 9 Sep 2009 20:18:41 -0700

I was curious if anyone on the list has any data or experience with low indoor humidity being a contributing factor to the spread of diseases and elevated complaints of illness including irritated eyes, coughing, sneezing, and sometimes nasal and chest congestion. The symptoms are often attributed to allergic reactions to dust or mold (the current "fall guy") in the indoor air which are not shown to be present at unusual levels during the investigation. I have conducted numerous indoor air quality investigations in the Las Vegas area where our outdoor humidity is usually well below 30%. The generally accepted concept that more, good quality outdoor air intake makes for better indoor air quality doesn't seem to pan out here. I find many of the problem buildings I investigate have a very high percentage of or 100% outdoor air intake. The air is typically well filtered (e.g., bag filters). However, there are numerous allergy-like complaints. When I measure relative humidity indoors it is often in the 20-30% range and even in the 10-20% range, especially in the winter. Could this lack of humidity also contribute to increase incidence of cold and flu transmission even though the air is being recirculated at a minimal level and indoor contaminants are being removed and/or significantly diluted in the indoor air? Thank you.

Dale Walsh, MS, CIH, LEED-AP

Walsh Certified Consultants, Inc.

Las Vegas, Nevada

From: CutzSent: Wed 9/9/2009 6:47 PMTo: Occ-Env-Med-LCc: OccHygPro List; UK Occupational Hygiene Discussion List; occ-env-med-listSubject: [occ-env-med-l] Flu Spread in temperate zones by aerosol, in tropics by contact: A hypothesis

Transmission of influenza virus in temperate zones is predominantly by aerosol, in the tropics by contact: A hypothesis

by Anice Lowen and Palese, Mount Sinai School of Medicine, NYUsing the guinea pig model, we have previously shown that the aerosol transmission of a seasonal human influenza virus is blocked by humid (80% relative humidity) or warm (30°C) ambient conditions. In contrast, we found that transmission by a contact route proceeded at high efficiency despite increased temperature or humidity. Based on these findings, and the observed seasonal behavior of influenza viruses in various regions of the world, we hypothesize herein that the predominant mode of influenza virus transmission differs in temperate and tropical climates. Specifically, we predict that aerosol transmission predominates during the winter season in temperate regions, while contact is the major mode of spread in the tropics. With this idea in mind, possible explanations for the current summer-time spread of swine-origin influenza viruses are discussed.URL: http://www.ncbi.nlm.nih.gov/rrn/articlerender.fcgi?acc=RRN1002

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