Re: weather
gsgs, thanks for the graphs ! :applause:
As I think this new thread matches, so I'd like to add my old singings about flu spread and air humidity to this place:
Air humidity modulates influenza transmission
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Re: Personal experience with H1N1 in Mexico
http://www.flutrackers.com/forum/showthread.php?t=104917&page=2
see post # 31 by Tonka (Thank you, Tonka !)
Quote:
Originally Posted by Tonka
Update from Puerto Vallarta...
"Things seem to be getting back to normal here. I put my daughter back in school last Monday. She goes to a small private school with only 8 kids in ea class, so I figured her odds are better of not catching the flu. I was surprised when she told me they are only required to wash their hands before lunch. Not good! I know lots of people who have been sick, but not one who has actually been confirmed H1N1. School has been extended until July 15th and now just announced school on Saturdays too. Ugh!
I know there are a few new cases here and there, but it does not seem to have exploded again with all public activities resuming. It does appear to be slowing down. For now. Humidity perhaps?(...)
Tonka "
Humidity ? Is there a possible relationship between humidity and influenza-transmission ? Obviously yes.
I found some sources to demonstate that there is a inverse relationship, that is: low humidity might increase influenza transmission.
Loosli CG, et al. Experimental air-borne influenza infection. I. Influence of humidity on survival of virus in air. Proc Soc Exp Biol Med 1943;53:205-6.
See slides 14+15 in presentation:
http://www.cdc.gov/niosh/npptl/resou...n Bridges"
and:
http://www.plospathogens.org/article...l.ppat.0030151
Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature Samira Mubareka1, John Steel1, Peter Palese1,2*
1 Department of Microbiology, Mount Sinai School of Medicine, New York, New York, United States of America, 2 Department of Medicine, Mount Sinai School of Medicine, New York, New York, United States of America
Abstract Top
Using the guinea pig as a model host, we show that aerosol spread of influenza virus is dependent upon both ambient relative humidity and temperature. Twenty experiments performed at relative humidities from 20% to 80% and 5 ?C, 20 ?C, or 30 ?C indicated that both cold and dry conditions favor transmission. The relationship between transmission via aerosols and relative humidity at 20 ?C is similar to that previously reported for the stability of influenza viruses (except at high relative humidity, 80%), implying that the effects of humidity act largely at the level of the virus particle. For infected guinea pigs housed at 5 ?C, the duration of peak shedding was approximately 40 h longer than that of animals housed at 20 ?C; this increased shedding likely accounts for the enhanced transmission seen at 5 ?C. To investigate the mechanism permitting prolonged viral growth, expression levels in the upper respiratory tract of several innate immune mediators were determined. Innate responses proved to be comparable between animals housed at 5 ?C and 20 ?C, suggesting that cold temperature (5 ?C) does not impair the innate immune response in this system. Although the seasonal epidemiology of influenza is well characterized, the underlying reasons for predominant wintertime spread are not clear. We provide direct, experimental evidence to support the role of weather conditions in the dynamics of influenza and thereby address a long-standing question fundamental to the understanding of influenza epidemiology and evolution.
and:
http://www.pnas.org/content/106/9/3243
Absolute humidity modulates influenza survival, transmission, and seasonality 3. Jeffrey Shamana,1 and
4. Melvin Kohnb
+Author Affiliations
3. aCollege of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331; and
4. bPublic Health Division, Oregon Department of Health Services, 800 NE Oregon, Suite 772, Portland, OR 97232
2. Edited by Burton H. Singer, Princeton University, Princeton, NJ, and approved January 7, 2009 (received for review July 16, 2008)
Abstract
Influenza A incidence peaks during winter in temperate regions. The basis for this pronounced seasonality is not understood, nor is it well documented how influenza A transmission principally occurs. Previous studies indicate that relative humidity (RH) affects both influenza virus transmission (IVT) and influenza virus survival (IVS). Here, we reanalyze these data to explore the effects of absolute humidity on IVT and IVS. We find that absolute humidity (AH) constrains both transmission efficiency and IVS much more significantly than RH. In the studies presented, 50% of IVT variability and 90% of IVS variability are explained by AH, whereas, respectively, only 12% and 36% are explained by RH. In temperate regions, both outdoor and indoor AH possess a strong seasonal cycle that minimizes in winter. This seasonal cycle is consistent with a wintertime increase in IVS and IVT and may explain the seasonality of influenza. Thus, differences in AH provide a single, coherent, more physically sound explanation for the observed variability of IVS, IVT and influenza seasonality in temperate regions. This hypothesis can be further tested through future, additional laboratory, epidemiological and modeling studies.
Now, take a look on climate graphs in Mexico City (lowest humidity in April !) and correlate to the number of cases at that time.
http://www.climatetemp.info/mexico/
So, the story of humidity and influenza-transmission might be more than a tale.
... and to add a new story: Take a look on the data of air humidity in Scotland (Edinburgh for example, sorry no data for Glasgow at that link !?) and England (London for example).
http://www.climatetemp.info/united-kingdom/edinburgh.html
http://www.climatetemp.info/united-kingdom/
Note, that air humidity is a matter of altitude and temperature, of course. But for all that, couldn't it be part of an explanation for swine flu to have hit Scotland so badly ?
also see thread:
http://www.flutrackers.com/forum/showthread.php?t=108301
