Image copyright Getty Images

History has repeatedly shown that contagion makes an easy bedfellow with human conflict.

Take the poliovirus outbreak in Syria - and Israel and Egypt too - caused by related strains that can be traced back to Pakistan.

War and insurgency provide the ideal conditions for bacteria and viruses to take a foothold, so it is little surprise that poliovirus has become entrenched - endemic - in Pakistan and Afghanistan and has now re-emerged in the Middle East.

Similarly in Africa, political obstruction to vaccination campaigns means that poliovirus continues to circulate in northern Nigeria and igniting an outbreak in war-torn Somalia and the wider Horn of Africa.

Chronicles of contagion 165 AD: Roman soldiers returning from the Parthian war spark the Antonine Plague (probably smallpox) that ravages the Roman Empire.

1155: Emperor Barbarossa contaminates drinking water by disposing human corpses in wells in Italy.

1618-48: The Thirty Years War. Typhus fever caused by a bacterium spread through the faeces of blood-sucking lice was rampant and lead to the cancellation of some battles.

1763: British settlers give two blankets and a handkerchief from a smallpox hospital to two visiting Native American chiefs.

1805-14: The Napoleonic wars. Typhus fever wreaked havoc, killing more French soldiers than the war effort itself.

1853-56: Crimean war. British forces are decimated by cholera outbreaks.

1870-71: Franco-Prussian war. A particularly aggressive form of smallpox virus, originating in France, was introduced into Prussia by French prisoners of war incarcerated in camps. This spread through the civilian population, but not to the Prussian soldiers - they had been protected.

1914-18: World War I. Across the world the influenza pandemic kills millions. In Russia, peace was followed by widespread famine and a constant flow of refugees blighted by cholera, dysentery, malaria, typhoid and typhus.

1939-45: World War II. The Japanese poison more than 1,000 Chinese wells with cholera and typhus and drop plague-infested fleas.

2011: The CIA was reported to have established fake vaccination programmes in Pakistan to secure DNA samples during the "war on terror" and the search for Osama Bin Laden. The ensuing mistrust has hampered legitimate polio vaccine programmes.

2012-13: Environmental samples test positive for the presence of poliovirus in Egypt, Israel, the West Bank and the Gaza Strip and cases of polio reported in Syria.

May 2013: WHO report on the isolation of wild poliovirus from a young girl in Somalia, which had been polio-free since 2007.

Many public health experts believe that the lack of vigorous vaccination programmes meant that this was an outbreak waiting to happen.

The evidence is clear. These viral strongholds are threatening the global polio eradication programme.

Breeding grounds

Throughout history, infectious diseases have strongly influenced and been influenced by war, as Matthew Smallman-Raynor, professor of analytical geography at the University of Nottingham, explained: "While the nature of warfare has changed down the ages, the link between war and disease remains as strong as ever.

"Today, as in the past, the wartime collapse of hygiene and healthcare systems means that familiar infections rapidly re-establish themselves opportunistically in war-torn populations."

Civilians and soldiers end up living in crowded and insanitary conditions, ideal breeding grounds for a range of bacterial, viral and parasitic infections. In Syria, a typhoid epidemic has taken hold in the eastern province of Deir Ezzor.

Damage to road networks leaves healthcare workers unable to get vaccines and medicines to the people needing them.

Most vaccines have to be kept cool until they are used, but interruptions to power supplies and lengthy journeys prevent this.

In Syria, poor vaccine coverage, coupled with overcrowding, lack of clean water and poor sanitation, is undoubtedly helping fan the flames of the poliovirus outbreaks.

But it is not just overcrowding and poverty that cause problems. Mass movement of troops and refugees greatly facilitates the spread of infectious disease.

Many civil wars in Africa have been accompanied by increases in infectious diseases, such as HIV. There is even anecdotal evidence of Lassa fever outbreaks due to refugees eating infected rats to survive.

Depths of time

Image copyright Getty Images Image caption Belgian troops in World War I

Vast mobilisation of troops during World War I undoubtedly played a part in one of the most devastating contagions of modern history - the 1918 influenza pandemic.

Although widely known as the Spanish flu, no one knows for sure where the virus originated. Some believe it was introduced into Europe by American soldiers, although accounts of serious respiratory diseases in Europe in earlier years can also be found.

Three waves of infection led to the demise of 50 million to 100 million people worldwide - around one in 18 people - and more than twice as many people as the war itself.

According to Prof Smallman-Raynor, the impact of war and infection can be traced back to the depths of time.

"Down the centuries, infectious diseases that have spread in consequence of war have decimated the fighting strength of armies, caused the suspension and cancellation of military operations and brought havoc to the civil populations of belligerent and non-belligerent states alike.

"Indeed, the available evidence yields a surprising statistic.

"Until relatively recent times at least, the greatest human losses in wartime were not due to bombs and bullets but, rather, losses from infections disseminated in both military and civilian populations," he said.

Germs as weapons

Nothing musters disease quite like war.

Humans were quick to cotton on to the destructive power of infectious diseases and used them to attack.

The nefarious use of smallpox in North American conflicts perhaps stands out above all others.

Image copyright SPL Image caption Smallpox killed nearly a third of people infected

Several accounts describe how European settlers used this virus to inflict suffering and death on Native Americans.

So perhaps it is of little surprise that the occupying British forces, when faced with the later civil unrest in the American War of Independence, turned to their old ally for help.

Before the advent of vaccination, the way to protect individuals from severe smallpox infection was to give them a small and controlled dose of smallpox itself. This is known as variolation.

Smallpox Image copyright SPL Caused by the variola virus

The virus originated more than 3,000 years ago in India or Egypt

Symptoms include fever, muscle pain, headache, tiredness and the distinctive rash

It killed 30% of those infected

More than 300 million people were thought to have died from smallpox in the 20th century alone

Up to 80% of survivors were marked with deep pitted scars, mostly on the face

But variolated people are infectious to others - a fact not lost on the British generals who, on at least two occasions, sent variolated people to spread death and disease among the rebellious Americans.

George Washington, realising the risk, ordered mass variolation of his own troops - an action that no doubt helped win the war.

And war efforts have also been used to justify and shield unethical research, none more so than in Nazi Germany, as Paul Weindling, Wellcome Trust research professor in medical history at Oxford Brookes University, explained.

He said: "The attack on the Soviet Union and the North African campaign prompted bacteriologists and the SS to conduct large-scale research in concentration camps and psychiatric hospitals.

"Thousands of inmates were deliberately infected with malaria, hepatitis and typhus in order to test vaccines and drugs."

The perpetrators were prosecuted at the Nuremberg medical trial and one of the outcomes was the Nuremberg code on permissible research, which requires that individuals involved in medical research give their voluntary consent.

The current poliovirus outbreaks are sad reminders that infectious diseases are one of the few true beneficiaries of war.

The progress on polio eradication has been monumental, but overall success is hanging by a thread.

At the eleventh hour, will war, insurrection and mistrust give succour to poliovirus?

After so much progress and effort I sincerely hope not, but only time will tell.