The 1918 influenza pandemic, also known as the Spanish flu, was the deadliest epidemic in world history.
An estimated 500 million worldwide were infected, and the death toll was anywhere from between 20 to 100 million.
Influenza, or flu, is a virus that attacks the respiratory system. It is highly contagious: when an infected person coughs, sneezes or talks, droplets are transmitted into the air and can be inhaled by anyone nearby.
A person can also be infected by touching something with the flu virus on it, and then touching their mouth, eyes or nose.
Although a pandemic of the influenza virus had already killed thousands in 1889, it was not until 1918 that the world discovered how deadly the flu could be.
Here are 10 facts about the 1918 Spanish flu.
1. It struck in three waves across the world
The first wave of the 1918 pandemic took place in the spring of that year, and was generally mild.
Those infected experienced typical flu symptoms – chills, fever, fatigue – and usually recovered after several days. The number of reported deaths was low.
In the autumn of 1918, the second wave appeared – and with a vengeance.
Victims died within hours or days of developing symptoms. Their skin would turn blue, and their lungs would fill with fluids, causing them to suffocate.
In the space of one year, the average life expectancy in the United States plummeted by a dozen years.
A third, more moderate, wave hit in the spring of 1919. By the summer it had subsided.
2. Its origins are unknown to this day
The 1918 flu was first observed in Europe, America and parts of Asia, before rapidly spreading across every part of the world within a matter of months.
It remains unknown where the particular strain of influence – the first pandemic involving the H1N1 influenza virus – came from.
There is some evidence to suggest that the virus came from a bird or farm animal in the American Midwest, travelling among the animal species before mutating into a version that took hold in the human population.
Some claimed the epicentre was a military camp in Kansas, and that it spread through the US and into Europe via the troops who travelled east to fight in the First World War.
Others believe it originated in China, and was transported by labourers heading for the western front.
3. It did not come from Spain (despite the nickname)
Despite its colloquial name, the 1918 flu did not originate from Spain.
The British Medical Journal referred to the virus as “Spanish flu” because Spain was hit hard by the disease. Even Spain’s king, Alfonso XIII, reportedly contracted the flu.
In addition, Spain was not subject to the wartime news censorship rules that affected other European countries.
In response, Spaniards named the illness the “Naples soldier”. The German army called it “Blitzkatarrh”, and British troops referred to it as “Flanders grippe” or the “Spanish lady”.
4. There were no drugs or vaccines to treat it
When the flu hit, doctors and scientists were unsure what caused it or how to treat it. At the time, there were no effective vaccines or antivirals to treat the deadly strain.
People were advised to wear masks, avoid shaking hands, and to stay indoors. Schools, churches, theatres and businesses were shuttered, libraries put a halt on lending books and quarantines were imposed across communities.
Bodies began to pile up in makeshift morgues, while hospitals quickly became overloaded with flu patients. Doctors, health staff and medical students became infected.
To complicate things further, the Great War had left countries with a shortage of physicians and health workers.
It was not until the 1940s that the first licensed flu vaccine appeared in the US. By the following decade, vaccines were routinely produced to help control and prevent future pandemics.
5. It was particularly deadly for young and healthy people
Most influenza outbreaks only claim as fatalities juveniles, the elderly, or people who are already weakened. Today, flu is especially dangerous for under 5-year-olds and those over 75.
The 1918 influenza pandemic, however, affected completely healthy and strong adults between 20 and 40 years of age – including millions of World War One soldiers.
Surprisingly, children and those with weaker immune systems were spared from death. Those aged 75 and above had the lowest death rate of all.
6. The medical profession tried to play down its severity
In the summer of 1918, the Royal College of Physicians claimed the flu was no more threatening than the “Russian flu” of 1189-94.
The British Medical Journal accepted that overcrowding on transport and in the workplace was necessary for the war effort, and implied that the “inconvenience” of the flu should be quietly borne.
Individual doctors also did not fully comprehend the severity of the disease, and tried to play it down to avoid spreading anxiety.
In Egremont, Cumbria, which saw an appalling death rate, the medical officer requested the rector stop ringing the church bells for each funeral because he wanted to “keep people cheerful”.
The press did likewise. ‘The Times’ suggested that it was probably a result of “the general weakness of nerve-power known as war-weariness”, while ‘The Manchester Guardian’ scorned protective measures saying:
Women are not going to wear ugly masks.
7. 25 million people died in the first 25 weeks
As the second wave of the autumn hit, the flu epidemic spiralled out of control. In most cases, haemorrhages in the nose and lungs killed victims within three days.
International ports – usually the first places in a country to be infected – reported serious problems. In Sierra Leone, 500 out of 600 dock workers fell too sick to work.
Epidemics were quickly seen in Africa, India and the Far East. In London, the spread of the virus became far more deadly and contagious as it mutated.
10% of the entire population of Tahiti died within three weeks. In Western Samoa, 20% of the population died.
Each division of the US armed services reported hundreds of deaths each week. After the Liberty Loan parade in Philadelphia on 28 September, thousands of people became infected.
By the summer of 1919, those who were infected had either died or developed immunity, and the epidemic finally came to an end.
8. It reached almost every single part of the world
The 1918 epidemic was of a truly global scale. It infected 500 million people across the world, including those on remote Pacific Islands and in the Arctic.
In Latin America, 10 out of every 1,000 people died; in Africa, it was 15 per 1,000. In Asia, the death toll reached as high as 35 in every 1,000.
In Europe and America, troops travelling by boat and train took the flu into cities, from where it spread to the countryside.
Only St Helena in the South Atlantic and a handful of South Pacific islands did not report an outbreak.
9. The exact death toll is impossible to know
The estimated death toll attributed to the 1918 flu epidemic is usually at 20 million to 50 million victims worldwide. Other estimates run as high as 100 million victims – around 3% of the world’s population.
However it is impossible to know what the exact death toll was, due to the lack of accurate medical record-keeping in many infected places.
The epidemic wiped out entire families, destroyed whole communities and overwhelmed funeral parlours across the world.
10. It killed more people than World War One combined
More American soldiers died from the 1918 flu than were killed in battle during the First World War. In fact, the flu claimed more lives than all of the World War One battles combined.
The outbreak turned the previously strong, immune systems against them: 40% of the US navy were infected, while 36% of the army became ill.
Featured image: Emergency hospital during 1918 influenza epidemic, Camp Funston, Kansas (National Museum of Health and Medicine)