Influenza and the weather

By: Dr. Jeff Masters , 1:14 PM GMT on May 04, 2009

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It is well known that influenza hits hardest in winter--November to March in the Northern Hemisphere, and May to September in the Southern Hemisphere. In fact, the name influenza comes from the Italian word influenza, meaning "influence"--referring to the "influence of the season" (winter) in causing the illness. In the tropics, where there is little change in seasons, influenza occurs year-round (though increased incidence has been noted in rainy seasons--Viboud et al., 2006). Do the cold temperatures and lower humidities of winter cause increased transmission of the flu virus? If so, why is the current H1N1 swine flu outbreak doing so well, now that it is May, traditionally the end of flu season in the Northern Hemisphere? Or could it be that indoor crowding, lack of sunlight lowering vitamin D levels, and a more depressed immune system in winter are largely responsible, as some researchers have suggested?

Flu infections increase under cold or dry conditions
To test these hypotheses, researchers at the Mount Sinai School of Medicine in New York did a study in 2007 that looked at flu transmission among guinea pigs, which are highly susceptible to human influenza and easily transmit the virus to other guinea pigs (Lowen et al., 2007). The animals were placed in adjacent cages, so that infections could occur by airborne transmission, but not by direct contact (guinea pig lovers will be happy to know that the influenza virus-infected guinea pigs did not display detectable symptoms of disease--weight loss, fever, sneezing, and coughing--during the experiments). By carefully controlling temperature and humidity, the scientists were able to study the effects of each. They found that the animals shed much more of the virus--and over a longer period of time--at cold temperatures, which led to increased infection rates. The animals' immune system showed no signs of stress from the cold weather, arguing against the idea that cold conditions lead to increased infections by lowering the immune system. Lower humidities were also found to increase flu transmission rate, though the variation of infection rate with humidity was more complicated. The scientists built a model (Figure 1) to fit the data, and proposed that lower humidity increased infection rates through two mechanisms:

1) The stability of influenza virons in the suspended aerosol particles infected creatures cough out is dependent upon the humidity. Viruses are most stable at low RH (20%-40%), least stable at intermediate RH (50%), and stable again at high RH (60%-80%) (Schaffer et al., 1976). Thus, the virus has better staying power at the low moisture levels typical of winter.

2) At high RH (80%), exhaled respiratory droplets grow quite large as water vapor condenses around them, and these drops quickly settle to the ground under the force of gravity. Thus, even though the virus is stable at high humidities, it settles out of the atmosphere quickly, and cannot contribute to influenza virus spread.


Figure 1. A model of influenza transmission rates at 68°F (20°C) (dashed line) and 41°F (5°C) (solid line), as a function of relative humidity. Transmission efficiency is highest at low relative humidity, when influenza virions in an aerosol are relatively stable, and exhaled respiratory droplets stay small and don't settle out under the force of gravity. Transmission is diminished at intermediate humidity when virus particles are relatively unstable, but improves in parallel with influenza virus stability at higher humidities. At high humidity, evaporation from exhaled particles is limited, respiratory droplets settle out of the air, and transmission is blocked. At cold temperatures (solid line), transmission is more efficient than at warm temperatures (dashed line), but is reduced to a rate of 50% at higher humidities. Image credit: Lowen, A.C., S. Mubareka, J. Steel, and P. Palese, 2007, "Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature", PLos Pathogons, October 2007.

The researchers found no guinea pig infections at 86°F (30°C), which implies that in tropical climates, people may transmit the virus by direct contact rather than by coughing and sneezing. A second study Lowen et al., 2009) confirmed this idea--at least among guinea pigs. The authors concluded, "To our knowledge, we demonstrate for the first time that cold temperatures and low relative humidity are favorable to the spread of influenza virus. Although other factors likely contribute to the periodicity of influenza epidemics, it is clear that air temperature and RH could play an important role. Influenza virus transmission indoors could potentially be curtailed by simply maintaining room air at warm temperatures (>20 °C) and either intermediate (50%) or high (80%) RHs".

Climate change and influenza
The results of this study imply that global warming may significantly reduce influenza world-wide, since a warmer climate will also be more humid. Typically, there are between three and five million cases of severe flu and up to 500,000 deaths worldwide each year. In the United States alone, an average of 41,400 deaths and 1.68 million hospitalizations are attributed to influenza each year. A warmer world should reduce these numbers, if the current research is correct. However, these gains must be balanced against the possibility that malaria will become more widespread in a warmer world, since malaria kills about one million people per year.


Figure 2. Combined flu and pneumonia deaths in the United Kingdom during the great 1918 flu pandemic showed that the flu had three distinct peaks: one in June - July (a relatively mild form of the disease), followed by an extremely deadly outbreak in October, then another during the winter of 1918 - 1919. The 1918 flu pandemic infected 1/3 of the world's population, killing 50 - 100 million people. Strangely, the October peak occurred almost world-wide, with Bombay, India and Boston, Massachusetts peaking the same week. Image credit: Jordan, E., "Epidemic influenza: a survey", Chicago: American Medical Association, 1927.

Flu pandemics show little seasonality
The current Mexican H1N1 swine flu outbreak is seemingly unusual, since it is hitting at the end of the traditional flu season, in April - May. However, when a new flu strain develops that humans have no immunity to, the new strain is less constrained by seasonality. According to Dr. Jeffery Taubenberger, the virologist who helped isolate the genetic code of the virus responsible for the great 1918 flu pandemic, "Historical records since the 16th century suggest that new influenza pandemics may appear at any time of year, not necessarily in the familiar annual winter patterns of inter-pandemic years, presumably because newly shifted influenza viruses behave differently when they find a universal or highly susceptible human population." Indeed, the 1918 flu pandemic reached its peak in September - October (Figure 2), and the most recent flu pandemic, the 1968 Hong Kong flu, began in July. It wouldn't surprise me if the current flu outbreak dies down in the Northern Hemisphere over the summer months, as the combined effects of high temperatures, higher humidities, less indoor crowding, and increased sunlight interfere with its spread. However, we need to be ready for the virus to reappear in the Fall--potentially in a mutated, more virulent form--such as occurred during the 1918 flu pandemic.

References
Lowen, A.C., S. Mubareka, J. Steel, and P. Palese, 2007, "Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature", PLos Pathogons, October 2007.

Lowen, A.C., S. Mubareka, J. Steel, and P. Palese, 2009, "High Temperature (30°C) Blocks Aerosol but Not Contact Transmission of Influenza Virus", Journal of Virology, June 2008, p. 5650-5652, Vol. 82, No. 11 0022-538X/08/$08.00+0 doi:10.1128/JVI.00325-08

Schaffer, F.L., M.E. Soergel, and D.C. Straube, 1976, "Survival of airborne influenza virus: effects of propagating host, relative humidity, and composition of spray fluids", Arch Virol 51: 263-273.

Viboud, C, W.J. Alonso, and L. Simonsen, 2006, "Influenza in tropical regions", PLoS Med 3: e89 doi:10.1371/journal.pmed.0030089.

Vitamin D and influenza links:
http://www.medicalnewstoday.com/articles/51913.ph p
http://www.sciencedaily.com/releases/2008/08/0808 11195629.htm
http://www.vitamindcouncil.org/science/research/v itamin-d-and-influenza.shtml

Jeff Masters

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Making MODUs safer in hurricanes

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The 12 semisubmersible mobile offshore drilling units that went adrift during Hurricanes Katrina and Rita in 2005 caused neither pollution damage nor loss of life, but did blow a hole in industry’s comfort with existing MODU mooring criteria. It was not the first time a MODU had gone adrift in a storm, but it was the first widespread recognition that the consequences of mooring failure had changed.

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Member Since: July 3, 2005 Posts: 426 Comments: 129093
Quoting Weather456:
I don't get it? Why all the hostility about JFV and why did he change his handle. I just found out the other day that PE was not a new person but JFV.


I have no problem with JFV; I have no problem with any blogger as long as I don't see any foul language. I was simply pointing that he is not banned indefinitely as we thought he was...
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Quoting Weather456:
I don't get it? Why all the hostility about JFV and why did he change his handle. I just found out the other day that PE was not a new person but JFV.


LOL where have you been. Under a rock?
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241. N3EG
Quoting Skyepony:
Abstract (It's not climate change related...I swear:)

Cannell JJ, Vieth R, Umhau JC, Holick MF, Grant WB, Madronich S, Garland CF, Giovannucci E.

In 1981, R. Edgar Hope-Simpson proposed that a 'seasonal stimulus' intimately associated with solar radiation explained the remarkable seasonality of epidemic influenza. Solar radiation triggers robust seasonal vitamin D production in the skin; vitamin D deficiency is common in the winter, and activated vitamin D, 1,25(OH)2D, a steroid hormone, has profound effects on human immunity. 1,25(OH)2D acts as an immune system modulator, preventing excessive expression of inflammatory cytokines and increasing the 'oxidative burst' potential of macrophages. Perhaps most importantly, it dramatically stimulates the expression of potent anti-microbial peptides, which exist in neutrophils, monocytes, natural killer cells, and in epithelial cells lining the respiratory tract where they play a major role in protecting the lung from infection. Volunteers inoculated with live attenuated influenza virus are more likely to develop fever and serological evidence of an immune response in the winter. Vitamin D deficiency predisposes children to respiratory infections. Ultraviolet radiation (either from artificial sources or from sunlight) reduces the incidence of viral respiratory infections, as does cod liver oil (which contains vitamin D). An interventional study showed that vitamin D reduces the incidence of respiratory infections in children. We conclude that vitamin D, or lack of it, may be Hope-Simpson's 'seasonal stimulus'.


I've heard the same said about Vitamin D and multiple sclerosis. I've taken D since I was diagnosed with MS in 2003, and have had no flare-ups in the last 5 years, half as many colds as usual, and no flu.

Your results may vary.
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JFV's blog

If the account was banned, WU would have informed you
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I don't get it? Why all the hostility about JFV and why did he change his handle. I just found out the other day that PE was not a new person but JFV.
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Quoting futuremet:
By the way, I checked JFV'S new account, and it is no longer banned...


If admin wanted to have a bit of fun, they could un-ban it, but change the password. That way the banned one could see everyone talking to him, but not be able to actually log in and reply.

He would pull out hair over that.
Member Since: August 16, 2007 Posts: 6 Comments: 12463
237. HTV
Quoting hahaguy:


It's a joke.

Ditto, seemed like everything west of 50 was headed for his house.
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Quoting futuremet:
By the way, I checked JFV'S new account, and it is no longer banned...


God be with us.
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Quoting futuremet:
By the way, I checked JFV'S new account, and it is no longer banned...


Dam, get prepared LOL
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By the way, I checked JFV'S new account, and it is no longer banned...
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Quoting HTV:

Why NOLA? Did JFV move there?


It's a joke.
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232. HTV
Quoting hahaguy:


Nah, I gotta say NOLA.

Why NOLA? Did JFV move there?
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Quoting SomeRandomTexan:
what else does your magical ball tell ya Weather456?


That hurricane season begins June 1.
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ill brb... gotta leave the office and go somewhere really quickly... keep the answers coming, i will be back in a few to check them out!!!
Member Since: August 30, 2007 Posts: 0 Comments: 1857
what else does your magical ball tell ya Weather456?
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Quoting Weather456:


My magic ball says somewhere heading towards to Florida.


Nah, I gotta say NOLA.
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But out of seriousness, the most likely place would be the Caribbean.
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Quoting nrtiwlnvragn:
213. atmoaggie

I know you like the background detailed stuff and I stumbled accross this website on Review of the NCEP Production Suite. Several good presentations, don't know if you already have it or not.


Thanks nrt. I am certainly going to look through those.
Member Since: August 16, 2007 Posts: 6 Comments: 12463
Quoting SomeRandomTexan:
a little piece of trivia...

Where will the first tropical storm form at in 09?

Have fun!


My magic ball says somewhere heading towards to Florida.
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DING DING DING!!!!!

The prize goes to PressLord...haha!
Member Since: August 30, 2007 Posts: 0 Comments: 1857
...over water...
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a little piece of trivia...

Where will the first tropical storm form at in 09?

Have fun!
Member Since: August 30, 2007 Posts: 0 Comments: 1857
As of 1100 AM today, www.cdc.org shows the following graph of confirmed laboratory cases:
Alabama 4
Arizona 17
California 30
Colorado 7
Connecticut 2
Delaware 20
Florida 5
Idaho 1
Illinois 8
Indiana 3
Iowa 1
Kansas 2
Kentucky* 1
Louisiana 7
Maryland 4
Massachusetts 6
Michigan 2
Minnesota 1
Missouri 1
Nebraska 1
Nevada 1
New Hampshire 1
New Jersey 7
New Mexico 1
New York 73
North Carolina 1
Ohio 3
Oregon 3
Pennsylvania 1
Rhode Island 1
South Carolina 15
Tennessee 1
Texas 41 1
Utah 1
Virginia 3
Wisconsin 3
TOTAL (36) 279 cases 1 death
Member Since: September 3, 2008 Posts: 0 Comments: 21568
good in wind already recorded a wind gust of 100kmh with it no problems its good for 200 kmh so they say
Member Since: July 15, 2006 Posts: 175 Comments: 54858
i use same station oz its a durable little unit works great as for cumlus it was only one i could fine and the best part its free and works with WU
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eeeeek!!!!


Link
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Hello:

I have purchased a ProWeather Station TP1080WC. Here is the link: ProWeatherStation.com

I'm going to mount this station to my mini-van for this hurricane season.

Question: Alot of people are using Cumulus software. Is this the best one to use? Is there something better?

Thanks for responding...

CycloneOz---
Member Since: August 26, 2006 Posts: 10 Comments: 3892
test
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Nino 3.4 region warming up:
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213. atmoaggie

I know you like the background detailed stuff and I stumbled accross this website on Review of the NCEP Production Suite. Several good presentations, don't know if you already have it or not.
Member Since: September 23, 2005 Posts: 14 Comments: 11274
Quoting nrtiwlnvragn:



This site is a mirror of Tropical Atlantic


Thanks, nrt, found that one. Let us hope it sticks around.

I couldn't access tropicalatlantic, or it's IP by nameserver, from machines in Slidell, Mobile, Huntsville AL, Seattle, or Woods Hole MA. (all with different nameservers and ISPs) Safe to say tropicalatlantic is apparently quite unreachable.

(Yes, I do know that I tend to over do things, thank you. I always have a machine available, though.)
Member Since: August 16, 2007 Posts: 6 Comments: 12463
Quoting Skyepony:
We conclude that vitamin D, or lack of it, may be Hope-Simpson's 'seasonal stimulus'.


I'll take Vit D over nicotine anyday. Thanks for this great info! :)
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211. IKE
Quoting captainhunter:
176. IKE

Hello IKE. Particularly nasty cell over Gulf Breeze right.


Most of the precip in the Florida panhandle is now starting to diminish.
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that is a pretty impressive flare-up of storms over Africa... if this can hold together, maybe it could be the first official tropical wave of 09. What do you guys think about it?
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203. stillwaiting

Cool site. Thanks.
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Quoting atmoaggie:
Guys,

Did http://tropicalatlantic.com disappear? I cannot even find it on any nameservers.

If you can access it, please let me know and try to get the IP address. That would simply mean they have a nameserver issue, but we could still access it directly by IP.

Any other way of thoroughly decoding a dropsonde?



This site is a mirror of Tropical Atlantic
Member Since: September 23, 2005 Posts: 14 Comments: 11274
Quoting weathermanwannabe:
Question (as I can't find it on the menu selctions)....How do I upload a new "avatar" to my blog entries?.......Thanks.


When you upload a new image down towards the bottom there should be a box and next to it should say "make this my profile picture" check that.
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Question (as I can't find it on the menu selctions)....How do I upload a new "avatar" to my blog entries?.......Thanks.
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I've become a little addicted to ISS and hubble watching since you first introduced me to that site,Thanks Oss!!!
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Link
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Quoting CaneWarning:


I don't think it will hold together once it makes it over water. We will see though.


yea thats been the trend so far in 09'
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196 Ok, I want to ensure I do this right.

I need to start smoking and get rid of my sunscreen and I should be pandemic proof, thats easy. :) jk


200- I lost that link, do you still have it.
Member Since: June 12, 2005 Posts: 6 Comments: 8186
oss:we'll be able to see the ISS both in the evening and early morning starting on the 10/11 of may....twice a day we'll be able to see a very bright ISS go over our area!!!
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Quoting stillwaiting:



I'm more immpressed w/the area of disturbed weather still over africa emerging!!!


I don't think it will hold together once it makes it over water. We will see though.
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Quoting Tropicsweatherpr:
Is this the first Tropical Wave of 2009 or there is no data to confirm that?

img



I'm more immpressed w/the area of disturbed weather still over africa emerging!!!
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Quoting Tropicsweatherpr:
Is this the first Tropical Wave of 2009 or there is no data to confirm that?

img


Been a few very well organized but unofficial Tropical waves back in Early-Mid April.
Member Since: July 8, 2005 Posts: 259 Comments: 24489
196. Skyepony (Mod)
Abstract (It's not climate change related...I swear:)

Cannell JJ, Vieth R, Umhau JC, Holick MF, Grant WB, Madronich S, Garland CF, Giovannucci E.

In 1981, R. Edgar Hope-Simpson proposed that a 'seasonal stimulus' intimately associated with solar radiation explained the remarkable seasonality of epidemic influenza. Solar radiation triggers robust seasonal vitamin D production in the skin; vitamin D deficiency is common in the winter, and activated vitamin D, 1,25(OH)2D, a steroid hormone, has profound effects on human immunity. 1,25(OH)2D acts as an immune system modulator, preventing excessive expression of inflammatory cytokines and increasing the 'oxidative burst' potential of macrophages. Perhaps most importantly, it dramatically stimulates the expression of potent anti-microbial peptides, which exist in neutrophils, monocytes, natural killer cells, and in epithelial cells lining the respiratory tract where they play a major role in protecting the lung from infection. Volunteers inoculated with live attenuated influenza virus are more likely to develop fever and serological evidence of an immune response in the winter. Vitamin D deficiency predisposes children to respiratory infections. Ultraviolet radiation (either from artificial sources or from sunlight) reduces the incidence of viral respiratory infections, as does cod liver oil (which contains vitamin D). An interventional study showed that vitamin D reduces the incidence of respiratory infections in children. We conclude that vitamin D, or lack of it, may be Hope-Simpson's 'seasonal stimulus'.
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Quoting captainhunter:
Link

You mean this?


Yes,that one.
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Link

You mean this?
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.