La Niña and flu

From the Columbia University’s Mailman School of Public Health

Does the La Niña weather pattern lead to flu pandemics?

Worldwide pandemics of influenza caused widespread death and illness in 1918, 1957, 1968 and 2009. A new study examining weather patterns around the time of these pandemics finds that each of them was preceded by La Niña conditions in the equatorial Pacific. The study’s authors–Jeffrey Shaman of Columbia University’s Mailman School of Public Health and Marc Lipsitch of the Harvard School of Public Health—note that the La Niña pattern is known to alter the migratory patterns of birds, which are thought to be a primary reservoir of human influenza. The scientists theorize that altered migration patterns promote the development of dangerous new strains of influenza.

The study findings are currently published online in PNAS.

To examine the relationship between weather patterns and influenza pandemics, the researchers studied records of ocean temperatures in the equatorial Pacific in the fall and winter before the four most recent flu pandemics emerged. They found that all four pandemics were preceded by below-normal sea surface temperatures—consistent with the La Niña phase of the El Niño-Southern Oscillation. This La Niña pattern develops in the tropical Pacific Ocean every two and seven years approximately.

The authors cite other research showing that the La Niña pattern alters the migration, stopover time, fitness and interspecies mixing of migratory birds. These conditions could favor the kind of gene swapping—or genetic reassortment—that creates novel and therefore potentially more variations of the influenza virus.

“We know that pandemics arise from dramatic changes in the influenza genome. Our hypothesis is that La Niña sets the stage for these changes by reshuffling the mixing patterns of migratory birds, which are a major reservoir for influenza,” says Jeffrey Shaman, PhD, Mailman School assistant professor of Environmental Health Sciences and co-author of the study.

Changes in migration not only alter the pattern of contact among bird species, they could also change the ways that birds come into contact with domestic animals like pigs. Gene-swapping between avian and pig influenza viruses was a factor in the 2009 swine flu pandemic.


While a recent paper posited a link between influenza pandemics and strong El Niño events, authors of the current paper note that this 2011 analysis was based on flawed data. They propose to test the La Niña-influenza theory by studying influenza genetics, avian migration patterns and climate data.

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January 16, 2012 7:18 pm

Yes, and more than 97% of all murders occur within two weeks of a new or full moon.

David B
January 16, 2012 7:18 pm

Coincidence or causation?

January 16, 2012 7:20 pm

One probably has to look at conditions in the year or two before the pandemic. Generally a pandemic starts mildly in the Northern Hemisphere flu season, picks up momentum in the Southern Hemisphere season, then roars through the Northern Hemisphere the following year. So whatever flu virus is responsible for a pandemic started in the human population the year before and likely in the animal populations the year before that.

Jason Calley
January 16, 2012 7:24 pm

Or perhaps La Nina is associated with altered solar activity or increased cloud cover, either of which could decrease levels of Vitamin D in billions of people.
Or maybe the study if wrong.

January 16, 2012 7:44 pm

Nice theory but didn’t the 2009 pandemic start in pigs in Mexico. It was a swine flu that learned to live in humans. Nothing to do with birds. Does La Nina influence the migratory patterns of pigs?

January 16, 2012 7:44 pm

interesting how I occasionally have the option of being ‘first cab off the rank’.
maybe because I’m in oz, the europeans are sleeping, and our american publisher is aiming to post before going to bed ? gottalove that global community !
these posts go to my facebook page and emails – works for me ! I don’t know why more blogs don’t publish on facebook, it’s a great way of spreading the word !
re today’s post – there’s an implicit message of the benefits of a warmer climate.
given our inability to modify weather, the obvious thing to do is to make various controlled environments. in my opinion there is much that can be done to ameliorate external conditions at the domestic level. heat sinks and passive solar jump to mind.
In the case of flu, I like the ‘2 metre rule’ – keep at least that far away from the carrier.
have a great day folks.

Steve from Rockwood
January 16, 2012 7:49 pm

So a strange bird meets a pig and everyone gets sick? Not convinced. If La Nina generates more cold conditions and that forces more people closer together, then maybe. Otherwise just another case of too much research money.

January 16, 2012 7:58 pm
January 16, 2012 7:59 pm

Interesting assertion….but what is the null hypothesis…?

January 16, 2012 8:02 pm

Interesting. Those four years are certainly Big Nina years. They struck a bell in my mind immediately, from my various failed attempts to connect Nina with other things!
The bird theory is dubious … I’m inclined to go along with Jason above, on vitamin D and sunshine in general.

January 16, 2012 8:31 pm

So the flu flew over the cuckoo’s nest next? Mann oh mann, I shouldn’t talk about Mann’s residence like that. Perhaps the theory is for the birds, or perhaps not. An interesting look at how the genome might change to something not seen previously though.

January 16, 2012 8:31 pm

quite good on politics of sience this fellow
what is he doing in weather research?

F. Ross
January 16, 2012 8:32 pm

jorgekafkazar says:
January 16, 2012 at 7:18 pm
Yes, and more than 97% of all murders occur within two weeks of a new or full moon.


January 16, 2012 8:32 pm

Deaths are always tragic – but the 2009 H1N1 “pandemic” was ⅓ as deadly to those who caught it than the average ‘flu and killed about 20 times fewer people than other varieties usually do. I wish they’d admit they were wrong about it, stop making excuses and shut the hell up.

Charles Gerard Nelson
January 16, 2012 8:33 pm

Jorgeka…you’re closer to the truth than you know!
The origin of the term Influenza is Latin and refers to the Influence of the Planets on the occurrence of pandemic illness.

January 16, 2012 8:38 pm

So we need to look out for next year, since we are in a strong La Niña right now.

January 16, 2012 9:01 pm

And, clearly, capitalism must replaced by socialism and America must be destroyed if the UN and Western schoolteachers are to save humanity from future flue pandemics, tra-la.

John F. Hultquist
January 16, 2012 9:07 pm

Thousands of strategically placed wind turbines might help.

Luther Wu
January 16, 2012 9:09 pm

Published in PNAS?
There was a time when that phrase meant something to me; a time before I viewed The Academy as politically compromised.
Still, NAS may be no worse that the rest of the vocal and published scientific community at present.
It’s sad, really.

Werner Brozek
January 16, 2012 9:11 pm

But La Nina brings colder weather on the average. Perhaps coldness lowers the resistance of people. Is warmer weather better for health? Did this get past peer review?
P.S. More than 97% of all murders occur within two weeks of a full moon. There is no need to add ‘new moon’, is there?

Al Gored
January 16, 2012 9:12 pm

While there may be something to this, however minor and SPECIFIC, any summary that simply talks about “birds” or the “migration pattern of birds” is inherently false, and ridiculous.
Which birds, EXACTLY? There are thousands of species following different migration routes, for the species that do migrate at all.
And the influence of La Nina on any of them varies.
Just from that initial smell test I strongly suspect this research is pure junk.

January 16, 2012 9:37 pm

I opened the window – and in flew ENSO.

Mike the convict
January 16, 2012 9:50 pm

Not avaian, but aviation is the cause of the spread of pandemics not Global Warming, unless you are implying that more people go on holidays when it’s hotter or something. The ability to fly quickly between countries while infected with say Dengue Fever and before the symptoms become noticable should be the first level of inquiry. Not blaming Global Warming for changed migratory patterns of birds.
Very droll jorgekafkazar.

January 16, 2012 10:31 pm

cause and effect??? so all those ice creams consumed in the summer months are responsible for the excess of drownings that happen in warmer weather????

January 16, 2012 11:10 pm

Colds and flus are not caused (in part) by cold weather but by the change in weather. That is why they are most common at the beginning of winter or the beginning of summer. It has something to do with reduced immunity under mild temperature stress.
Nothing to see here … move along.

Dr. Dave
January 16, 2012 11:45 pm

This one really is amusing. I love articles that delve into subjects in which I actually have some level of expertise. I’m left cross eyed and confused when Willis dissects computer models, but human disease is something with which I am familiar. The possible link between migratory birds and influenza was posited MANY years ago. Many decades after the event, epidemiologists were puzzled by how the great influenza pandemic of 1918 managed to devastate very remote settlements in the far northern hemisphere that were geographically (and politically) isolated from the WWI battlefields of Europe or the USA. They hypothesized that perhaps migratory birds may have been the vector. Far more likely is that just one or two infected humans made their way up to the far north and infected entire communities that had little or no inherent or acquired immunity and were huddled together in close living quarters. Influenza is a respiratory disease and its primary mode of transmission is via aerosol human-to-human contact (hence the masks). By contrast the common cold (or the killer variants I seem to contract about every two or three years) is transmitted primarily by fomites (i.e. infected stuff you touch and inadvertently ingest). It seems unlikely the Inuit would have birds coughing on them. But an infected human is the most infectious (i.e. shedding virus like crazy) a couple days BEFORE they manifest symptoms. This is one of the reasons influenza is so dangerous to human populations. There are ample opportunities to infect many others before you even know you’re sick. And outbreaks occur during cold months not because of the cold but because of human behavior when the surrounding environment is cold – they cluster together in smaller and warmer areas.
Then there is this petty little point from the article, “Jeffrey Shaman, PhD, Mailman School assistant professor of Environmental Health Sciences and co-author of the study.” This guy just doesn’t impress me as a go-to guy on a human disease that has been extensively studied for over six decades. There are literally armies of M.D., Ph.D. epidemiologists both in the private and public sector who have devoted their entire careers to studying influenza in humans and other animals. This guy got a “climate change” grant and ran with an old, tired hypothesis to make some headlines. The big mystery about influenza is the pathogenicity of the mutated strains. The transmission is almost entirely human-to-human.

January 17, 2012 12:00 am

CynicalScientist says: January 16, 2012 at 7:44 pm

Nice theory but didn’t the 2009 pandemic start in pigs in Mexico. It was a swine flu that learned to live in humans. Nothing to do with birds. Does La Nina influence the migratory patterns of pigs?

All this makes perfect sense, when pigs fly…

January 17, 2012 12:09 am

Personally, I think it is a very plausible hypothesis accompanying a numerically interesting observation — excellent science. I don’t think they are asserting that this is a “proven conclusion”, but rather that there is an interesting correlation and a plausible cause. It also has nothing to do with CAGW, so it isn’t political.
Ordinarily, one would then use the hypothesis to predict that our next flu pandemic is most likely to occur after the next La Nina, and perhaps do some targeted research studying the specific migratory patterns of birds that are known to carry variants of the flu that can cross over to humans. Over sufficient time, the hypothesis would either be contradicted or be supported to the point where it was difficult to doubt (although the mechanism might be imperfect or statistical).
Similar causal relations with weather are, after all, hardly unknown. Malaria and rainfall. Flu and time of year. It’s not like weather and climate don’t have any effect on the biosphere that can modulate disease…

January 17, 2012 2:58 am

1918, 1957, 1968, 2009
The first two and the last two are about forty years apart. The middle is about 10. Even if I knew zilch about La Nina, I would ask is the period of the event about 10 years and if yes why did it skip the possible other 6 cycles?.

January 17, 2012 3:52 am

Here’s a good one – Economic disasters are more likely in warmer weather.
On mild or warm nights, all the bars at London’s Canary Wharf and Square Mile are packed full of hard drinking bankers – unlike cold, rainy nights. The next day, after a mild night, there are plenty of severe hangovers and possibly even a few drunks at the desk – leading to an increase in reckless, ill considered trading decisions.

January 17, 2012 4:30 am

Major Armed conflict involving the United States shows better correlation.
1918 World War One
1957 The Korean War
1968 The Vietnam War
2009 The Second Gulf War (Iraq and Afghanistan)
That leaves out World War 2 and the First Gulf War, which gives a 4 out of 6 correlation ( 66% very poor). Correlation with La Nina is about 4 out of more than 30 ( less than 13% comical, absurd, whatever)

January 17, 2012 4:45 am

Define “pandemic”. From where I sit, the last “flu pandemic” was entirely overhyped by the media. I kept hearing about H1N1, but I did not know one person who had it. I only knew of one city where it was widespread, and even there it wasn’t bad. So are we defining “pandemic” as a disease that spreads rapidly and has infected many people or as a disease that the media, which lives on bad news, makes out to be worse than it really is?

January 17, 2012 5:06 am

1918 was the first world war returnees after ages in filth and mud.
and when global travel started up
the 80s one. hm? one soldier and then a vax that killed and caused gullain Barre etc.
so wonder how they could link Bats and Hendra in aus?
or Nipah and pigs in asia?
funny how labs were working on a manmade blend of swine bird etc using DNA 1918 from arctic just before the usa outbreak too?

Pamela Gray
January 17, 2012 6:59 am

Flu is spread by physical contact with infected surfaces. It can also be spread through the air if the air is conducive to virus and bacterial “piggyback rides”. This is the case regardless of what the oceans are doing. The potential of pandemic is always there in that the pathogens are always ready to attach to a surface or a ride. So what might be the trigger of infection increase? Same as it is for staff infections in hospitals and enclosed spaces. Proximity to and concentration of the pathogen. La Nina and El Nino produce regional opposite weather effects. In some regional places we gather, in others we disperse from one another. These living changes affect proximity to and concentration of the pathogens all around us. Some studies will find La Nina to blame, others will find El Nino to blame. It’s all regional and then becomes pandemic. Case closed.

Paul Linsay
January 17, 2012 7:04 am

Read “The Great Influenza” about the 1918 outbreak that killed 100 million people. It started as swine flu in the Midwest, spread in the troop trains, camps, and barracks of the US soldiers preparing to go to Europe to fight in WWI, from there it spread to US cities, and finally brought by them to Europe. It was a time when the germ theory of disease was still not accepted by a major part of the medical profession. It had nothing to do with La Nina.

January 17, 2012 8:29 am

A bit off topic, but the same old,
Side effects and effectiveness of ‘wonder-drug’ Tamiflu under the microscope as Department of Health faces awkward questions over mass prescriptions
As well as questioning issues surrounding Tamiflu, researchers behind the review also claimed the makers of the drug refused to hand over raw data to help them with their appraisal.
Swiss pharmaceutical giant Roche claimed Tamiflu reduced the number of patients who needed to be hospitalised after becoming infected with swine flu.

January 17, 2012 9:24 am

Would the cool dry weather following La Nina increase transmission rates too?

January 17, 2012 9:46 am

Poorer food production is probably also a factor.

January 17, 2012 9:54 am

When your facts don’t fit the data, make the data fit your facts. From Wikipedia:
“A Wisconsin study published in the Journal of the American Medical Association in September 2010, reported that findings showed that the 2009 H1N1 flu was no more severe than the seasonal flu.”
In fact WHO reported the largest number of world-wide deaths from the 2009 H1N1 flu at 18,036. With 2011 US highway fatalities reported at just under 36,000, I give the 2009 H1N1 pandemic a big yawn.

January 17, 2012 9:55 am

Excuse me, the 2011 highway fatalities are just under 33,000. My bad.

January 17, 2012 10:07 am

Long, long before the alarmism about ‘Bird Flu” it was known that human flus pretty much came from birds and the flu strains floating around in bird populations.
The thing the alarmists don’t tell you is that for every several HUNDRED strains in the bird populations only one will affect humans at all, much less cause any serious epidemics.
The bird flus we’ve seen in recent years is more mass hysteria by alarmists than anything else.
YES, bird flus will make for more human flus in the future. So what? Are we going to kill all the wild birds? We killed tens of millions of domesticated fowl during one of the recent scares. Are we going to stop the birds from migrating? No. It is okay to kill chickens, but not wild birds – it is against the bleeding heart principles of the alarmists.
Flus will come, and flus will go. Compared to past epidemics pandemics in the future just ain’t going to happen. Medicine deals with it far too well. The 1918 Pandemic – raise you hands if you’d rather have the medicice available then vs now.
All pandemics are not equal.
Ths supposed pandemic of 2009 was a technical pandemic, but a pandemic in name only. Due to pressures (some of it from Big Pharma), exceedingly low thresholds are now set to designate an outbreak as a pandemic in the world. Those questionable trigger points were met – just barely – which meant that some nations were required by law to buy massive amounts of swine flu vaccine. That was even though several of those countries had little or no flu or deaths. Big Pharma made out like bandits.
SOMEONE is going to take advantage of any situation.
The deaths in 2009 were well over 90% of the numbers forecast. It was mostly (vastly mostly) just a bunch of screaming about the world coming to an end. When only a bit over 10,000 deaths occur in a world of 6 billion, it is a far cry from the good old days of pandemics, when 30% to 60% and more died.
When I hear the word pandemic, I yawn, because the people don’t know what they are talking about. 10,000 people were dying daily in 1918. It took well over half a year for the 2009 deaths to reach that number. In the meantime, the pandemics of heart disease and cancer took how many lives? Who is screaming bloody murder about those? Oh, right, those are old pandemics and are BORING. And they don’t sell newspapers, as the old saying goes.

Theodore White
January 17, 2012 11:38 am

It always surprises me how many of the comments above on the relation to climate/weather and human and animal health seeks to lower the bar on learning new things – rather than mouthing off as if one actually knows what they are talking about.
The Earth’s climate and weather are the result of a highly variable system forced by astronomical conditions in outer space. Our Earth lives in space, but many of the comments on the climate/weather presumes that the Earth is flat and is not part of a solar system.
If you study the history of pandemics from an astronomical view you will see that ‘influenza’ – meaning influenced by celestial bodies – are spread by means of astronomically-forced configurations relative to the Earth.
Cynical comments are not conducive to learning what one does not know. The appearance of such comments are brought about by reactionary narcissist attitudes that attempt to cover over the ignorance of what one does not know.
It is easier to dismiss rather than to first digest what one does not know and then to learn. The climate and resulting weather affects all living things on Earth. A highly variable gaseous water vapor climate planetary system as we have here on Earth tends to do that.
Pandemics are spread as a result of astronomically-forced climate conditions on the Earth’s environment – this has been well-known among expert forecasters who actually forecast.
There are plenty of historical scientific studies on this topic. But then again, it is much easier to dismiss what one does not know; since that way one does not have to learn anything new and can offer up mere critical comments and opinion as fact – when these are far, far from the truths of the matter.

Power Grab
January 17, 2012 12:43 pm

Some of the current advice of physicians with an alternative approach to avoiding the flu is to avoid sugar and have plenty of vitamin D in your system. I’m wondering if the late 1920s, late 1930s, late 1940s, late 1970s, late 1980s, and late 1990s were times when people had relatively less consumption of sugar and/or more exposure to sunlight and sources of the fat-soluble vitamins, of which vitamin D is one. Does anyone know how widespread the use of cod liver oil was in the 1920s and 1930s?
Another thing can make you feel like you have the flu is exposure to chemical poisons, e.g., pesticides and herbicides. I remember reading that the 1918 epidemic was likely associated with the ways they disposed of the chemical warfare weapons that had been developed for World War One. I wonder if people had less exposure to these chemical agents in the low-flu eras.
FWIW, I had an ancestor who was a country doctor. They says he treated more than 70 patients for the Spanish flu and didn’t lose any of them.

January 17, 2012 12:51 pm

feet2thefire says:
January 17, 2012 at 10:07 am
Thank you, I was waiting for the WHOs change of how a “pandemic” was described to enter the fray.

January 17, 2012 6:38 pm

The cholera bacterium frequently plague the west coast of South America, and large-scale cholera outbreaks occur periodically. It has long been speculated that main reservoirs of the bacterium exist in the deep Pacific waters off the coast. El Ninos cause cold water upwells along South American coast bringing nutrient-rich cold water to the surface, and, it is theorized, the cholera bacteria.
I don’t know if a similar chain events could involve influenca – seems like the basic virus is endemic in SE Asia, and mutations of it first infect pigs, then is transferred to humans to start a new wave of influenza. But I would be surprised if cholera were the only bacteria dangerous to humans that the ocean harbors, and cyclical ocean events could result in cyclical pandemics.
I would think a young researcher would find this a fascinating area to explore.

January 17, 2012 6:49 pm

Power Grab: The 1918 flu virus has been recovered from tissue samples from frozen victims (buried in Alaska, Greenlad, etc). Researchers feel they pretty-well understand the virus, where and how it attacks the body, and why those who were otherwise the healthiest people suffered the most.
There seems to be no need to inject a possible human element to explain the course of the pandemic. Of course, that won’t stop those who believe that Man is the primary source of all evil in the universe from disparaging anything man-made.

January 17, 2012 8:29 pm

If I were to study this conjecture, the first thing that I would do would be to grab some longitudional data on global annual death from the flu and compare these with the incidence of La Ninas.
Having done that, very quicky, I would search around for another project with better prospects for a fruitful outcome.
But then, I’m not a climate scientist or even one tarred by that very sticky mildew.

Brian H
January 17, 2012 10:56 pm

Werner Brozek says:
January 16, 2012 at 9:11 pm
But La Nina brings colder weather on the average. Perhaps coldness lowers the resistance of people. Is warmer weather better for health? Did this get past peer review?
P.S. More than 97% of all murders occur within two weeks of a full moon. There is no need to add ‘new moon’, is there?

Blast!! Beat me to it.
My revised version sez, “More than 97% of all murders occur within one week of a full or new moon.” More confusing, therefore more likely to be accepted as troo and sicnigifant. Or SLT.

Bob Shapiro
January 20, 2012 2:43 am

“The study’s authors–Jeffrey Shaman of Columbia University’s Mailman School of Public Health…”
This sounds too much like a witch doctor operating through a correspondence school, for me to pass up.

February 12, 2012 7:57 am

One thing for sure – vitamin D deficiency is highly correlated with flu.
Vitamin D level tends to bottom out at the end of winter which makes it more likely to get flu. The lower, the more severity of flu. I’ve been taking 5,000 IU of vitamin D3 supplement a day during “school” year and I rarely got sick with anything even cold for the past 3 years. We get nothing from the sun due to weather and very little from food/drink (a cup of milk has only 100 IU if at all). Ever wonder why we get massive amount of vitamin D from the sun? Yet Dermatologists are yelling at us to stay out of the sun.
So… does La Nina cause bad weather that would force us to stay inside and see a lot less sun?

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