Re: Cold weather really does spread flu

[Guest guest]

now, place a N95 between the cages ...

[Guest guest]

I wonder if the same results would have obtained if the air flow had not been manipulated. Lee <jackalope_lepus@...> wrote: Cold weather really does spread flu* 12:19 19 October 2007* NewScientist.com news service* Debora MacKenzieScientists have finally confirmed what your mother knew all along –that flu spreads best in cold, dry weather.As the first few cases of the northern hemisphere's annual fluepidemic are trickling in this week, scientists may finally know whywinter is flu season. It

appears the virus lasts longer in cold, dryair, and our sluggish, cold-weather mucus cannot clear it out.Astonishingly it has taken until the publication of research this weekto settle the basic question about how flu spreads, and why it girdleseach hemisphere every year during winter. Ironically, that researchwas made possible by the rediscovery of a report by army doctors in 1919.Flu is hard to study in the lab because virtually no lab animals getit the way humans do. Mice, for example, do not get the same strains,or catch flu from each other. The most useful animal has been the ferret.Exhaled virusHowever, studying disease transmission requires too many animals to bepractical with ferrets. "They're big, they're expensive, and theybite," Palese of Mount Sinai Medical School in New York Citytold New Scientist.But in 1919, US Army doctors at Camp Cody in New Mexico reported(Journal of the

American Medical Association, vol 72 p1056) that the1918 flu pandemic had killed their guinea pigs – kept at the time formedical tests. "We didn't know guinea pigs got flu," says Palese. Theyare no longer popular lab animals, and no-one had tried them.So Palese's team exposed hundreds of guinea pigs to a human flu strainat different temperatures and humidities, in cages that allowed onlyair to pass from sick animals to well ones. This settled alongstanding dispute over whether flu can spread solely as an airborneinfection, or whether physical contact is needed. "It spread just inthe air they exhaled," says Palese. "Guinea pigs with flu don't coughor sneeze."Twin peaksAt room temperature, they found flu transmission peaks at low relativehumidity (20-35%) and again at 65%. It spread less well at around 50%humidity, and not at all over 80%. This parallels the stability of fluvirus in aerosol droplets at

different humidities, and also thedroplets' ability to remain airborne. At over 80% humidity, dropletscontaining flu virus themselves fall out of the air.The effect also happened too quickly to be due to dry air damagingnasal tissue so that it is not as effective a barrier to viruses,which has been suggested as a factor in humans.But temperature trumped humidity: at 5 °C animals caught flu athumidities that stopped the virus when it was warmer, possibly becausesick animals' noses shed virus two days longer at cooler temperatures.To find out why, Palese's team charted 13 early immune reactions ininfected animals, but they were unaffected by temperature. Mucus,however, normally flows up through our respiratory tracts to clear outcontaminants. "Mucus becomes more viscous as cold air hits our upperrespiratory tracts," he says. "So we can't clear the virus as easily."Journal reference: PLoS Pathogens (DOI:

10.1371/journal.ppat.0030151)http://www.newscientist.com/article/dn12808-cold-weather-really-does-spread-flu.html . Do one thing every day that scares you. Eleanor Roosevelt

[Guest guest]

What do you mean, ? Manipulated how? And what do you think

the results would have been?

Cold weather really does

spread flu

> * 12:19 19 October 2007

> * NewScientist.com news service

> * Debora MacKenzie

> Scientists have finally confirmed what your mother knew all along �

> that flu spreads best in cold, dry weather.

>

> As the first few cases of the northern hemisphere's annual flu

> epidemic are trickling in this week, scientists may finally know why

> winter is flu season. It appears the virus lasts longer in cold, dry

> air, and our sluggish, cold-weather mucus cannot clear it out.

>

> Astonishingly it has taken until the publication of research this week

> to settle the basic question about how flu spreads, and why it girdles

> each hemisphere every year during winter. Ironically, that research

> was made possible by the rediscovery of a report by army doctors in

1919.

>

> Flu is hard to study in the lab because virtually no lab animals get

> it the way humans do. Mice, for example, do not get the same strains,

> or catch flu from each other. The most useful animal has been the

ferret.

> Exhaled virus

>

> However, studying disease transmission requires too many animals to be

> practical with ferrets. " They're big, they're expensive, and they

> bite, " Palese of Mount Sinai Medical School in New York City

> told New Scientist.

>

> But in 1919, US Army doctors at Camp Cody in New Mexico reported

> (Journal of the American Medical Association, vol 72 p1056) that the

> 1918 flu pandemic had killed their guinea pigs � kept at the time for

> medical tests. " We didn't know guinea pigs got flu, " says Palese. They

> are no longer popular lab animals, and no-one had tried them.

>

> So Palese's team exposed hundreds of guinea pigs to a human flu strain

> at different temperatures and humidities, in cages that allowed only

> air to pass from sick animals to well ones. This settled a

> longstanding dispute over whether flu can spread solely as an airborne

> infection, or whether physical contact is needed. " It spread just in

> the air they exhaled, " says Palese. " Guinea pigs with flu don't cough

> or sneeze. "

> Twin peaks

>

> At room temperature, they found flu transmission peaks at low relative

> humidity (20-35%) and again at 65%. It spread less well at around 50%

> humidity, and not at all over 80%. This parallels the stability of flu

> virus in aerosol droplets at different humidities, and also the

> droplets' ability to remain airborne. At over 80% humidity, droplets

> containing flu virus themselves fall out of the air.

>

> The effect also happened too quickly to be due to dry air damaging

> nasal tissue so that it is not as effective a barrier to viruses,

> which has been suggested as a factor in humans.

>

> But temperature trumped humidity: at 5 �C animals caught flu at

> humidities that stopped the virus when it was warmer, possibly because

> sick animals' noses shed virus two days longer at cooler temperatures.

>

> To find out why, Palese's team charted 13 early immune reactions in

> infected animals, but they were unaffected by temperature. Mucus,

> however, normally flows up through our respiratory tracts to clear out

> contaminants. " Mucus becomes more viscous as cold air hits our upper

> respiratory tracts, " he says. " So we can't clear the virus as easily. "

>

> Journal reference: PLoS Pathogens (DOI: 10.1371/journal.ppat.0030151)

>

http://www.newscientist.com/article/dn12808-cold-weather-really-does-spread-flu.\

html

>

>

>

>

>

>

>

> . Do one thing every day that scares you. Eleanor Roosevelt

>

[Guest guest]

The article says that the airflow was directed towards the uninfected animals. I wonder what the results would have been if it had not been done that way but just allowed ambient air to move naturally between the infected and uninfected. Don <DCFrench@...> wrote: What do you mean, ? Manipulated how? And what do you thinkthe results would have been? Cold weather really doesspread flu> * 12:19 19 October 2007> * NewScientist.com news service> * Debora MacKenzie> Scientists have finally confirmed what your mother knew all along �> that flu spreads best in cold, dry weather.> > As the first few cases of the northern hemisphere's annual flu> epidemic are trickling in this week, scientists may finally know why> winter is flu season. It appears the virus lasts longer in cold, dry> air, and our sluggish, cold-weather mucus cannot clear it out.> > Astonishingly it has taken until the publication of research this week> to settle the basic question about how flu spreads, and why it girdles> each hemisphere every year during winter. Ironically, that research> was made

possible by the rediscovery of a report by army doctors in1919.> > Flu is hard to study in the lab because virtually no lab animals get> it the way humans do. Mice, for example, do not get the same strains,> or catch flu from each other. The most useful animal has been theferret.> Exhaled virus> > However, studying disease transmission requires too many animals to be> practical with ferrets. "They're big, they're expensive, and they> bite," Palese of Mount Sinai Medical School in New York City> told New Scientist.> > But in 1919, US Army doctors at Camp Cody in New Mexico reported> (Journal of the American Medical Association, vol 72 p1056) that the> 1918 flu pandemic had killed their guinea pigs � kept at the time for> medical tests. "We didn't know guinea pigs got flu," says Palese. They> are no longer popular lab animals, and no-one had tried

them.> > So Palese's team exposed hundreds of guinea pigs to a human flu strain> at different temperatures and humidities, in cages that allowed only> air to pass from sick animals to well ones. This settled a> longstanding dispute over whether flu can spread solely as an airborne> infection, or whether physical contact is needed. "It spread just in> the air they exhaled," says Palese. "Guinea pigs with flu don't cough> or sneeze."> Twin peaks> > At room temperature, they found flu transmission peaks at low relative> humidity (20-35%) and again at 65%. It spread less well at around 50%> humidity, and not at all over 80%. This parallels the stability of flu> virus in aerosol droplets at different humidities, and also the> droplets' ability to remain airborne. At over 80% humidity, droplets> containing flu virus themselves fall out of the air.> > The

effect also happened too quickly to be due to dry air damaging> nasal tissue so that it is not as effective a barrier to viruses,> which has been suggested as a factor in humans.> > But temperature trumped humidity: at 5 �C animals caught flu at> humidities that stopped the virus when it was warmer, possibly because> sick animals' noses shed virus two days longer at cooler temperatures.> > To find out why, Palese's team charted 13 early immune reactions in> infected animals, but they were unaffected by temperature. Mucus,> however, normally flows up through our respiratory tracts to clear out> contaminants. "Mucus becomes more viscous as cold air hits our upper> respiratory tracts," he says. "So we can't clear the virus as easily."> > Journal reference: PLoS Pathogens (DOI: 10.1371/journal.ppat.0030151)>http://www.newscientist.com/article/dn12808-cold-weather-really-does-spread-flu.html> > > > > > > > . Do one thing every day that scares you. Eleanor Roosevelt>

. Do one thing every day that scares you. Eleanor Roosevelt

[Guest guest]

> however, transmission was not observed when the > relative positions of the infected and uninfected animals were > reversed, suggesting that spread depended on the direction of > airflow in the room.

[Guest guest]

No, there was no directed air flow. Two standard glass rat cages, one

with an infected guinea pig and one with an uninfected one (which they

call a naive subject), were placed next to one another with one wall

in each replaced with a wire screen between to allow air expired by

either one to be inhaled by the other. It was set up in such a way

that there was no possibility of physical contact.

Because guinea pigs don't sneeze or cough, the virions were

transferred purely by expiration. It would be interesting to do the

same experiment with varying distances between the two pigs to

determine the effective infection range.

I assume that if they put a N95 filter in the path, as Sterten

suggested, that there would be no infection. I think that the problem

with N95 masks is not the efficacy of the filter, but the seals around

the edges.

>

>

> In einer eMail vom 31.10.2007 07:32:30 Westeurop�ische Normalzeit

schreibt

> rboylern@...:

>

> The article says that the airflow was directed towards the uninfected

> animals. I wonder what the results would have been if it had not

been done that

> way but just allowed ambient air to move naturally between the

infected and

> uninfected.

>

>

>

> I assume, they would have needed many more guinea pigs to find

significant

> results.

> They said, the experiments are being continued...

>

[Guest guest]

I think that this is the statement that caused the confusion: " So

Palese's team exposed hundreds of guinea pigs to a human flu strain

at different temperatures and humidities, in cages that allowed only

air to pass from sick animals to well ones " . It is easy to read that

statement as " allowed air to pass only from sick animals to well

ones " . By " only air " they mean no saliva or other physical material.

But there is no mention of directed air flow.

Cold weather really does

> spread flu

> > * 12:19 19 October 2007

> > * NewScientist.com news service

> > * Debora MacKenzie

> > Scientists have finally confirmed what your mother knew all along �

> > that flu spreads best in cold, dry weather.

> >

> > As the first few cases of the northern hemisphere's annual flu

> > epidemic are trickling in this week, scientists may finally know why

> > winter is flu season. It appears the virus lasts longer in cold, dry

> > air, and our sluggish, cold-weather mucus cannot clear it out.

> >

> > Astonishingly it has taken until the publication of research this week

> > to settle the basic question about how flu spreads, and why it girdles

> > each hemisphere every year during winter. Ironically, that research

> > was made possible by the rediscovery of a report by army doctors in

> 1919.

> >

> > Flu is hard to study in the lab because virtually no lab animals get

> > it the way humans do. Mice, for example, do not get the same strains,

> > or catch flu from each other. The most useful animal has been the

> ferret.

> > Exhaled virus

> >

> > However, studying disease transmission requires too many animals to be

> > practical with ferrets. " They're big, they're expensive, and they

> > bite, " Palese of Mount Sinai Medical School in New York City

> > told New Scientist.

> >

> > But in 1919, US Army doctors at Camp Cody in New Mexico reported

> > (Journal of the American Medical Association, vol 72 p1056) that the

> > 1918 flu pandemic had killed their guinea pigs � kept at the time for

> > medical tests. " We didn't know guinea pigs got flu, " says Palese. They

> > are no longer popular lab animals, and no-one had tried them.

> >

> > So Palese's team exposed hundreds of guinea pigs to a human flu strain

> > at different temperatures and humidities, in cages that allowed only

> > air to pass from sick animals to well ones. This settled a

> > longstanding dispute over whether flu can spread solely as an airborne

> > infection, or whether physical contact is needed. " It spread just in

> > the air they exhaled, " says Palese. " Guinea pigs with flu don't cough

> > or sneeze. "

> > Twin peaks

> >

> > At room temperature, they found flu transmission peaks at low relative

> > humidity (20-35%) and again at 65%. It spread less well at around 50%

> > humidity, and not at all over 80%. This parallels the stability of flu

> > virus in aerosol droplets at different humidities, and also the

> > droplets' ability to remain airborne. At over 80% humidity, droplets

> > containing flu virus themselves fall out of the air.

> >

> > The effect also happened too quickly to be due to dry air damaging

> > nasal tissue so that it is not as effective a barrier to viruses,

> > which has been suggested as a factor in humans.

> >

> > But temperature trumped humidity: at 5 �C animals caught flu at

> > humidities that stopped the virus when it was warmer, possibly because

> > sick animals' noses shed virus two days longer at cooler temperatures.

> >

> > To find out why, Palese's team charted 13 early immune reactions in

> > infected animals, but they were unaffected by temperature. Mucus,

> > however, normally flows up through our respiratory tracts to clear out

> > contaminants. " Mucus becomes more viscous as cold air hits our upper

> > respiratory tracts, " he says. " So we can't clear the virus as easily. "

> >

> > Journal reference: PLoS Pathogens (DOI: 10.1371/journal.ppat.0030151)

> >

>

http://www.newscientist.com/article/dn12808-cold-weather-really-does-spread-flu.\

html

> >

> >

> >

> >

> >

> >

> >

> > . Do one thing every day that scares you. Eleanor Roosevelt

> >

>

>

>

>

>

>

>

>

> . Do one thing every day that scares you. Eleanor Roosevelt

>

[Guest guest]

Sorry, my mistake. I missed this section, which was in one of the

pink blocks in the original paper:

" Naïve animals were placed behind infected animals, such that the

direction of airflow was toward the naïve animals. "

They weren't testing the efficacy of transmission by exhalation, only

the effects of temperature and humidity on the ability to become

infected, so I guess they wanted to be sure that they were efficiently

bathing the naive animals in virus laden air.

> >

> >

> > In einer eMail vom 31.10.2007 07:32:30 Westeurop�ische Normalzeit

> schreibt

> > rboylern@:

> >

> > The article says that the airflow was directed towards the

uninfected

> > animals. I wonder what the results would have been if it had not

> been done that

> > way but just allowed ambient air to move naturally between the

> infected and

> > uninfected.

> >

> >

> >

> > I assume, they would have needed many more guinea pigs to find

> significant

> > results.

> > They said, the experiments are being continued...

> >

>