Influenza and the weather
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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I might just sit back and watch
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Don't forget.. he threw global warming in there also.. only thing missing is politics.
Does that mean that discussing tropical weather would be off topic ??
LOL and good morning
And Global Warming too! :(
Yes!
Shear in that area is down to 10 to 20 knots with the tendency falling.
Influenza A(H1N1) - update 13
4 May 2009 -- As of 06:00 GMT, 4 May 2009, 20 countries have officially reported 985 cases of influenza A (H1N1) infection.
Mexico has reported 590 laboratory confirmed human cases of infection, including 25 deaths. The higher number of cases from Mexico reflects ongoing testing of previously collected specimens. The United States has reported 226 laboratory confirmed human cases, including one death.
The following countries have reported laboratory confirmed cases with no deaths - Austria (1), Canada (85), China, Hong Kong Special Administrative Region (1), Costa Rica (1), Colombia (1), Denmark (1), El Salvador (2), France (2), Germany (8), Ireland (1), Israel (3), Italy (1), Netherlands (1), New Zealand (4), Republic of Korea (1), Spain (40), Switzerland (1) and the United Kingdom (15).
There is no risk of infection from this virus from consumption of well-cooked pork and pork products.
It is considered prudent for people who are ill to delay international travel and for people developing symptoms following international travel to seek medical attention, in line with guidance from national authorities. Individuals are advised to wash hands thoroughly with soap and water on a regular basis and should seek medical attention if they develop any symptoms of influenza-like illness.
WHO advises no restriction of regular travel or closure of borders.
Further information on the situation will be available on the WHO website on a regular basis
and they are planing on going to level 6
LinkLink
Yes
...sniffle...sniffle...
...cough...
Link
I have found that both the Google Map and the EDIS maps are not updated well. For instance the Google map does not include cases noted for Georgia or Maine, EDIS map does not note the cases in South Carolina
Someone (forgive me, I cannot remember who) posted the link for HealthMap.org This map seems much more up to date. Make sure that other illnesses are unchecked so that you are only looking at the Oinky Doinky flu.
ADDED: Wish I could take credit for coining the phrase Oinky Doinky - alas that came from the Pyrates Deck
Leave it up to Dr. Masters to post what he wants to in his blog...on his site...LOL
you this put word right in to my mouth thanks i was this about to say that
whoa! some people take words out of context and get their undies all knotted up... look guys tone can not be displayed through words so take everything with a grain of salt... I love reading the blogs not people bickering. Keep up the good work Dr. Masters and everyone who is providing such excellent information.
(end of soap box)
--kman good eye
Its name was Enza.
I opened the window,
And in-flu-enza.
We used to jump rope to this rhyme... I looked it up and it came from the 1918 - 1919 influenza pandemic!
Re: 33 LOL Perspective
I too noticed that area has persisted and is worth keeping a eye on as the flow should take it WNW and then back due west towards the lower eastern seaboard...worth watching not much else going on in the ATL....
Another....
Ring around the rosy,
A pocketful of posies.
ashes, ashes.
We all fall down!.
I believe this one came from the Bubonic Plaque in England... We sang many variations.
In fact, many nursery rhymes have "hidden meanings".
As a child, we had no idea that both of these rhymes had "hidden meanings".
Link
About 9 out of 10 of those deaths are among people older than 65, Currie said. Most times, they already have health problems that the flu makes worse, he said.
"Regular influenza can be taxing," he said. "It causes their underlying disease to decompensate and then they don't have the reserves to get through it.
"While it may not be the direct cause listed on the death certificate, it certainly contributed."
One of the reasons medical experts are nervous about the swine flu outbreak is that many of the people who have died in Mexico have been young and otherwise healthy. The strains found in the United States have so far been weaker.
dates back to the Great Plague. A rosy rash, they allege, was a symptom of the plague, posies of herbs were carried as protection, sneezing was a final fatal symptom , and “all fall down” was exactly what happened.’ Another translation:Ring around the Rosie: people with the plague often had a bright rose-colored rash that people would see and make a large ring around them. A pocket full of posies: people without the plague often carried around posies, believing this would purify the air and protect them from getting ill. Ashes, Ashes: When people died, sometimes they would be burnt to ashes. Then those ashes would be put in a jar and buried. In this way, there was enough room in the graveyards for everyone. We all fall down: ‘falling down’ meant dying and many people did die.
Even the news networks are saying that we are getting carried away with the swine flu...
Mexico city has lowered their alert level...
Though we do need to get a handle on it before flu season gets into full swing later this year.
dates back to the Great Plague. A rosy rash, they allege, was a symptom of the plague, posies of herbs were carried as protection, sneezing was a final fatal symptom , and “all fall down” was exactly what happened.’ Another translation:Ring around the Rosie: people with the plague often had a bright rose-colored rash that people would see and make a large ring around them. A pocket full of posies: people without the plague often carried around posies, believing this would purify the air and protect them from getting ill. Ashes, Ashes: When people died, sometimes they would be burnt to ashes. Then those ashes would be put in a jar and buried. In this way, there was enough room in the graveyards for everyone. We all fall down: ‘falling down’ meant dying and many people did die.
President Barack Obama, in his weekly address on May 2, put it best: "Because we have it within our power to limit the potential damage of this virus, we have a solemn and urgent responsibility to take the necessary steps. I would sooner take action now than hesitate and face graver consequences later." Better safe than sorry - when it comes to diseases it's as clichÉd as washing your hands, and just as smart.
Weather456 I believe you may have been talking about the possibility of it being a tropical wave when coming off Africa... tia
Did you get those nasty storms last night?
Its interesting when you look at the Rhymes from our youth.... many had meanings that children often would not know or understand.
Thanks folks, very interesting, indeed. Makes one wonder about all those nursery rhymes. So who was Humpty Dumpty - other than a lost cause?
Wish I could stay for the fun. Work calls.
Pax, y'all
Entirely different system and genesis. These troughs spin up at the surface typically east of any upper level feature. Reason being, the upper divergence to the east of these feature induce surface lift and hence low pressure, that is, a trough of low pressure.
BETWEEN 55W AND 65W
530 AM EDT MON MAY 04 2009
.SYNOPSIS...SFC TROUGH ALONG 65W MOVES W TO 70W MON NIGHT THEN
DISSIPATES TUE NIGHT INTO WED. HIGH PRES BUILDS N OF AREA WED
THROUGH FRI.
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