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
Reader Comments
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thanks bro! didn't realize he was from Trinidad
Greetings after a while. Hope everyone is well. Fingers are crossed for a quiet season (3 1/2 weeks away already????). I stumbled across our Hurricane Emergency kit in the back storage room this past weekend. I hope the dust can keep gathering on it.
;>)
Despite meeting with former Florida emergency management chief Craig Fugate Monday, U.S. Sen. David Vitter, R-La., said he'll continue to block Fugate's confirmation as head of the FEMA until the Obama administration allows rebuilding projects in south Louisiana.
Awesome!!!!
well i like watchin tropics for it gives clues to possible outcomes and activity ahead as a prelude to the main coarse to follow
its a big picture but some can look and not see the picture or maybe not want to see the picture but there are lots of clues to be looking for sst's sal set up of ba high water vapour content dynamical flow of the mid upper lower levels set up and activity of african wave machine which by the way produces up to a hundred or more waves startin normally around this time right till end of sept early oct of all those waves be happy that only 10 to 15 will become anything at all
815. All I can say is plz have you supplies. Plz don't count on the Gov/Fema to help you within the first week of a major strike. Many church groups are strapped for cash. Bascially it DOES fall on you for your own survival.
This is very good advice. From someone who has been there. And been there...And learned the hard way.
Willie Drye
for National Geographic News
September 12, 2008
Hurricane Ike's expected massive storm surge and flooding have prompted National Weather Service officials to issue a rare and chilling "certain death" warning as the storm barrels toward the Texas coast tonight.
"We rarely issue this warning unless there is a severe, impending catastrophe," said Chris Sisco, a meteorologist at the National Hurricane Center in Miami. "It's very serious."
The warning reads: "Neighborhoods that are affected by the storm surge … and possibly entire coastal communities … will be inundated during the period of peak storm tide.
"Persons not heeding evacuation orders in single-family, one- or two-story homes may face certain death. … Widespread and devastating personal property damage is likely elsewhere."
Sisco said Ike's storm surge—a mound of water created by a hurricane's winds—could reach 20 feet (6.1 meters) around the center of the storm.
And the surge could be "funneled" as it is driven inland into some bays and rivers, causing the surge to rise to as much as 25 feet (7.6 meters) in some places, he said.
The National Weather Service advisory also warned that in some places, floodwaters could be as much as 9 feet (2.7 meters) deep more than 1 mile (1.6 kilometers) inland.
The center of Hurricane Ike is expected to make landfall late Friday night or early Saturday morning near Galveston, Texas, about 50 miles (80 kilometers) south of the metropolitan city of Houston.
Flooding Threat
As of Friday morning, Ike was a Category 2 hurricane with peak winds of about 105 miles (169 kilometers) an hour.
System is moving east at 35 mph and has a Tornado Watch with it. Be careful on the road.
Hi OZ, stay safe this year! I look forward to your vids, and hopefully they WILL educate some on the reasons to evacuate!
Tampa is a Risk city without a recent Strike in Living memory.
I shy away from belittling another's ones woes,be it a individual,or a City.
I'll let the one who Made the Mistake of staying tell ya from his own Mouth...in 2005
Since were yakking it over.
Chalmette,East of NOLA..Aug 29th 05
This year will be even harder for me if we have to leave, because pops, {hubbie} is much worse! But sense we are so close to the gulf, if something comes along this year, I will pack him up and be on my way!
Less than a month from the start of the season-may not be the time for a p!$$1n contest though
From the link:
It's not unusual for senators to hold presidential appointees for leverage during policy disputes. The Senate government affairs committee approved Fugate's nomination by a voice vote last week, and he has been well-received on Capitol Hill. But the full Senate can't vote until Vitter lifts his hold.
Many folks said,"I cant believe this could happen to me".
or... "I cant believe this HAS happened".
But the most memorable words I heard was from a First Responder who was in NOLA in 05,and was now beat from S & R in his own county.
His words were,..
"Just look how fast we went from talking about those Folks,to being those folks."
The look on that Guys face..,I'll never forget.
Even worse is if that happened after the storm already paid a visit to Miami or Tampa in a double hit.
I agree Keeper a direct hit on NYC would be a worst case scenario.As a veteran of the Rita evac, I don't think they can move that many people out in time.It would be a nightmare for any major city.
Yeah I learned the hard way AND I LEFT. LOL.But it was weeks before the MRE'S,water and ice showed up in my town. And even longer for some other smaller towns farther inland. And that was before the power was restored. And I can't even go there about FEMA.Sigh. Lets hope the next time its better for whoever it happens to.
"EMONG" has intensified into a typhoon as it continues to move closer to Northern Luzon.
Tropical Cyclone Bulletin #2
==================================
At 5:00 AM PhST, Typhoon Emong (Chan-hom) located at 15.1°N 116.4°E or 350 kms west-southwest of Iba, Zambales has 10 minute sustained winds of 120 km/h (65 knots) near the center with gustiness up to 150 km/h (80 knots). The storm is reported as moving northeast at 8 knots.
Warning Signals #2 (60-100 km/h winds)
==============================
Luzon Region
------------
1.Ilocos Norte
2.Abra
3.Ilocos Sur
4.La Union
5.Benguet
6.Pangasinan
7.Zambales
Warning Signals #1 (30-60 km/h winds)
==============================
Luzon Region
-----------
1.Apayao
2.Kalinga
3.Mt. Province
4.Ifugao
5.Nueva Vizcaya
6.Quirino
7.Nueva Ecija
8.Tarlac
9.Pampanga
10.Bataan
Residents living in low lying and mountainous areas under signal # 1 and 2 are alerted against flashfloods and landslides.
The rest of Central Luzon, Southern Luzon including Metro Manila will continue to experience occasional rains.
The public and the disaster coordinating councils concerned are advised to take appropriate actions and watch for the next bulletin to be issued at 11 A.M. today.
OMG - A hostage situation!!!
How anyone can think that it is a good idea to withhold the approval of the director of a Federal EMERGENCY Management Agency. Hopefully, no area (including LA) will have a need for FEMA any time soon.
O.O I'd be afraid for the EF-5 configuration.
Gotta love the weather.
I guess the EF-5 would be the entire Tampa Bay Rays equipped with baseball bats rather than just the two daughters.
The rain dance worked, huh?
2 questions:
Do you have Health and Life Insurance?
Have you ever seen the movie Jackass?
(Your scaring the children)
Quoting theshepherd:
Yeah, your right, implants would be fantasy....But, is a saliva sample for DNA too much to ask???
;>)
Which would be cheaper, DNA samples or tattoos j/k
Branding ! Seems applicable to those who challenge Mom Nature.
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