By Rachael Buchanan
In a quiet little village in Hampshire there's a very potent reminder of the power influenza can occasionally wield.
The lung samples provide important information
Lined up with the characteristic precision of a military cemetery are the graves of 318 Canadian soldiers, who lived and died here in Bramshott during the First World War.
As you move through the ranks of simple limestone headstones, the dates climb gently, sequentially; until you reach September 1918.
For the next few months, bodies poured into this little village graveyard.
In October and November, there were 137 deaths; on 8 November alone there were 12 funerals, and they were so overwhelmed some burials were held at night.
But this is not a roll call of war dead; most of these men were victims of the Spanish Flu Pandemic that swept the globe that year.
The Great War slew 15 million in 4 years. Influenza racked up a death toll three times that number in less than a third of the time.
Few people know more about the exceptional power of the 1918 flu pandemic than Professor John Oxford, of Queen Mary's College, London.
Oxford has dedicated most of his professional life to solving the molecular mystery behind one of history's most efficient serial killers; tracking its legacy around the globe, from Southwark to Spitzbergen.
Back in his East London laboratory he carefully opens up a battered cardboard box to reveal four blackened, irregular cubes, each about the size of a sugar lump.
These are lung samples from 1918 victims, carefully preserved in paraffin.
They may be nearly a century old but locked inside are samples of the virus.
These nuggets are more than biological curios to Oxford; they amount to a warning from history - the next global outbreak could be just as devastating, and just around the corner.
"I would class the potential threat from the next pandemic as exceeding high," he told BBC News.
"I don't think we have ever been so close to an outbreak; a global outbreak as we are now. Mother Nature has always been the greatest threat - bigger than any bio-terrorist," he warned.
Building a virus
The virus that is making Oxford and the world's flu experts nervous made its debut in the Far East around two years ago and has so far infected 44 people across Thailand and Vietnam, killing more than three-quarters of them.
Not a huge death toll, but then this new strain is still in its infancy. A flu virus particle is little more than a bag of genetic material with two types of protein sticking out of its shell; spikes that help it infect cells and then spread.
The haemagglutinin spike spears the body's cells and helps the virus enter where it hijacks our own cells' mechanics to replicate many times over.
The neuraminidase spike provides the escape route, rupturing the cell wall to release the newly made viruses and so spread the infection.
Flu strains are named for these two proteins "H" for haemagglutinin and "N" for neuraminidase. The 1918 virus was an early version of H1N1, and the other two pandemics of the last century represent mutations of one or both of these proteins; the 1956 strain being H2N2 and the 1968 strain, H3N2.
And Mother Nature's newest far eastern formula? H5N1.
These proteins are what the body's immune system targets - fine when your immune system is presented with something it has met before - it already has an antibody template to work with.
But when influenza generates totally new proteins, an H5 for example, the immune system is caught out - it has no template to build its defences.
Before it can learn how to build the right shaped antibodies, the whole body may succumb, overwhelmed by this novel virus.
This is what has killed those 32 victims in Thailand and Vietnam; their immune system did not catch up in time. New strains of flu are zoonotic diseases - they start in animals, usually chickens, and cross the species barrier to cause unique human infections.
The origin of the current H5N1 outbreak was chickens where it was particularly deadly. But for now each case has been an isolated example of bird to human transmission, a viral dead end.
Scientists will really worry when someone that already has human flu, also catches H5N1. Then, the two may combine, emerging as a new strain with the virulence of the chicken flu and the transmissibility of human flu.
The result - a deadly pandemic which in the age of easy international travel could spread around the globe in weeks.
So now around the world, influenza monitoring centres which study local flu outbreaks are watching out for novel strains, too.
Included in this network is the UK's Health Protection Laboratory in North London. At the moment it is business as usual, but the lab's head of Virology, Maria Zambon, is in no doubt what effect a new strain could have.
Bramshott: A warning from history
"We are worried that a new pandemic might turn out to be 'force 10 on the Richter scale' of new emerging viruses in humans," she said.
"It would cause an enormous global burden of disease and death and we are particularly concerned that it might well affect the young adult population and in doing so bring society to a halt."
Of course this is the 21st Century and medical science has undergone a revolution since the 1918 pandemic.
We have drugs and vaccines that can work against the virus. But the problem is that even this modern technology takes time to get up to speed.
First, the new strain has to emerge, and then a vaccine must be developed and millions of doses grown.
The minimum time span is around several months; by which time millions could be dead.