A CENTURY ago in 1920 an influenza pandemic was coming to an end. It had started two or three years before, perhaps in a Kansas army camp, and it would kill more people than died in the entire first world war.

This would be the most severe influenza pandemic in recorded history. It was caused by a virus of avian origin. There are various theories where it originated — none proven. It was first identified in US military personnel in Kansas in the spring of 1918. 

Some 500 million people, or a third of the world’s population, became infected with this virus, and at least 50 million died worldwide, with a death toll of 228,000 in Britain alone. 

The worldwide mortality rate is not known, but is estimated to have been between 10 and 20 per cent. Two of my wife Ann’s relatives were among those fatal flu victims.

Mortality was high in three groups of people — those younger than five years old; those between 20 and 40, and the over-65s. A unique feature of this particular pandemic was the high mortality in healthy younger people between 20 and 40. 

Despite much speculation and research over the last 100 years the reasons that this outbreak was so devastating are still not totally understood. 

Some factors include the absence of a vaccine to protect against infection, along with the absence of antibiotics to treat secondary bacterial infection. 

The war-torn situation in much of the world, with troops living in cramped, unhygienic conditions obviously added to the spread, as did frequent crowded troop movements.
  
Simple and obvious interventions such as isolation, quarantine, good personal hygiene, use of disinfectants and limitations of public gatherings were difficult or impossible to put in place. General ill-nourishment due to the war was another contributory factor. 

In order to put those 1920 casualty figures into perspective we need to be aware that populations have grown in the 100 years since. 

The world’s population in 1914, before the war, was a little over one-and-a-half billion, today it is over seven-and-a-half billion. Likewise, the British population has grown from 36 million in 1914 to 66 million today. 

So what is influenza? It is a very common infectious disease caused by a virus. Symptoms can be mild to severe and can include high fever, runny nose, sore throat, cough, joint and muscle pain and fatigue.

Symptoms typically begin two days after exposure to the virus and most last less than a week. The cough, however, may hang on much longer. Children may suffer diarrhoea and vomiting but these are not common in adults.

Complications of influenza may include viral pneumonia, secondary bacterial pneumonia, sinus infections and worsening of previous health problems such as asthma or heart failure.

The World Health Organisation (WHO) estimates that flu kills between 250,000 and 500,000 people every year around the world. It also causes severe illness in between three and five million.
 
The latest British figures available cover only England, where the average number of deaths in the 2014-15 to 2018-19 seasons was 17,000 deaths annually. This average figure varies a lot, with 1,692 deaths in 2018-19 and 28,330 deaths in 2014-15.

New strains like the present coronavirus can be even more devastating if the global population has no immunity to the particular virus.

That most devastating flu pandemic in 1918 was called “Spanish flu,” but there is no evidence that it came from Spain. 

That pandemic spread in three more or less simultaneous waves through Europe, Asia and North America. The actual origins of the virus are still unknown.

Another major pandemic was in 1957-58. First identified in China — and thus called Asian flu — it caused roughly two million deaths worldwide. 

The virus is thought to have emerged after a human form combined with a mutant flu strain in ducks. The strain has not circulated in humans since 1968, so much of the global population has not built immunity to this particular strain. Most of those who died from it were elderly.

The 1968-69 pandemic was first detected in Hong Kong and immediately named Hong Kong flu. 

The virus killed around one million people globally, with those over 65 most vulnerable. This virus still circulates today causing various, mostly small, outbreaks.

In 1997, for the first time, an influenza virus was found to spread directly from birds to people. It became known as bird flu. These bird-flu infections were linked to poultry markets. 

The first outbreak in Hong Kong killed six of 18 people infected. The WHO has recorded 598 cases since 2003, with 352 deaths. Most deaths from bird flu are in Egypt, Indonesia, Vietnam and China. So far, the virus has not adapted to spread easily between humans.

Another of the new strains was the swine-flu virus that originated in Mexico in 2009. The virus is a combination of a Eurasian swine-flu virus with another strain that was itself a mix of bird, swine and human flu virus. The strain went on to kill more than 18,000 people around the world.

Now we have coronavirus. That story is moving far too quickly for me to keep up with it and I’m certainly not qualified to cover the viral science involved. What I do know is that new casualty figures appear every few minutes. 

Even more important to some people it seems is the fact that share prices that are being pushed down by inconvenient sickness and death in China and across the world. That’s capitalism for you. 

President Donald Trump has declared the whole pandemic as a hoax but that might be wishful thinking as he has systematically dismantled the US’s pandemic response capabilities since taking office and proposed further huge cuts to both the Centres for Disease Control and Prevention and the National Institutes of Health.

Racists, always ready to play the blame game, are creeping out from beneath their stones and encouraging attacks and boycotts on Chinese takeaways and restaurants. No amount of swearing at civil servants by a bully of a Foreign Secretary will stop that.

One thing is clear. It won’t be the invisible man, Prime Minister Johnson and his Tory crew that will be our first line of defence against this new danger. It will be the heroes of our wonderful NHS. 

Thank goodness millions of us have fought to defend it from Tory attacks and threats of privatisation. That’s a fight that, like the battle against flu and all other disease, needs to carry on.