The spring of 1918 brought with it the usual yearly flu, popping up here and there. People sickened. Some died. Some turned a peculiar purple-black and had trouble breathing. There was little alarm. In retrospect, this was the first of three waves.

The world paid little attention, as the war was all-consuming. In Canada, the military was the largest employer, controlling much of the country’s manufacturing and many of its hospitals. All around the globe, troops and war support workers were on the move, travelling in vast numbers across land and sea, from Asia and North America to the trenches and battlefields of Europe. News that could hurt morale or benefit the enemy was censored in most countries to aid the war effort. And means of mass communication were limited. In Canada, there were few telephones. And no radio or television.

Canada’s federal government wasn’t keeping an eye on disease outbreaks. Influenza was not a reportable disease when the pandemic began. In fact, doctors didn’t use the term “influenza” much  at the time; instead, they spoke of catarrhs or purulent bronchitis. Many doctors and nurses were also out of the country, serving in the war. Canada didn’t even have a federal department of health. And federal politicians who might have been able to raise the alarm weren’t gathered in Ottawa during the worst of the outbreak — Parliament rose near the end of May that year, not to sit again until late February 1919, when the pandemic had largely run its course.

But on May 28, 1918, Canadians got their first hint of the devastation that was to come. It was in a story carried by newswires from Spain, one of the few countries whose media outlets were free from censorship because it was not a combatant in the war. The “grip” or influenza had struck Madrid, the Canadian Press reported, paralyzing the Spanish capital’s business world and sickening about 30 per cent of those from other parts of the country. It was, the story said, a “strange disease.”

Within a week, readers of the Toronto Star discovered that 700 had already died from what it dubbed “the plague.” The Times of London was calling it the  “Spanish epidemic.” The moniker stuck, not because the pandemic had begun in Spain, but because the first reports emerged from there.

A month later, when the hospital ship Araguayan reached Halifax Harbour from England, 23 per cent of its passengers and crew were sick with influenza, writes historian Humphries in his 2013 book The Last Plague: Spanish Influenza and the Politics of Public Health in Canada. Rather than leap into action, federal officials dragged their feet. It was two weeks later that the officially named “Spanish Influenza” was included in Canada’s list of “the graver forms of quarantinable disease” and steps were taken to isolate the ship’s sick, notes Humphries. But this was still the first wave. The virus wasn’t yet on the loose in Canada. The worst was yet to come.

Flu viruses are magicians. They constantly reshape themselves, figuring out fiendish new ways to spread, always one step ahead of the body’s immune system. While three main types of the flu affect people — A, B and C — only the A type can cause pandemics. Flu viruses also live in birds and mammals and by definition, a pandemic flu virus must start in an animal, typically a waterfowl or pig. The virus breaks free from that avian or swine host, jumps to people and, either by picking up some genes from an existing human flu virus, or by mutating its own, transforms from an animal flu virus into a new type of human flu virus. Because it’s new, we have no immunity to it.

Novelty alone is not enough to make it dangerous, explains Arnold Monto, professor of epidemiology and global public health at the University of Michigan in Ann Arbor who is known as the “guru of flu.” To set the stage for a pandemic, this new flu virus also has to be able to spread extensively among people and cause severe illness and death.

Viruses have been wildly successful at that for more than 500 years. Medical sleuths track flu pandemics back at least to the Middle Ages and perhaps earlier. They have found evidence that suggests the occurrence of at least 14 flu pandemics since 1500, including three since 1918. The most recent, in 2009, began in Mexico, surprising researchers who expected it would emerge in Asia, says Theresa Tam, Canada’s chief public health officer. “The more we uncover about the flu virus,” she says, “the less we actually know.”

One thing is sure. Each of the three post-1918 flu pandemics, and almost all modern seasonal influenza A cases around the world, evolved from that savage 1918 mutation. But no version has come near the 1918 virus for sheer, explosive virulence, writes Jeffery K.  Taubenberger, the chief of viral pathogenesis and evolution at the National Institutes of Health in the United States who helped sequence its genome and later reconstructed the virus itself. Nobody knows precisely where the 1918 virus emerged — theories range from the U.S. Midwest to China to an army camp in France — but it made a third of the people then on Earth — about half a billion — clinically ill.

At one time, historians believed troops returning from the battlefields of Europe carried the virus home. Humphries’ meticulous historical detective work disproved that. In fact, returning troops were stuck in Europe from July until late September 1918 for fear their ships would be attacked by German U-boats. By the time soldiers started to arrive home in October, the pandemic’s second wave had already spread from coast to coast. And when the majority of soldiers returned after the armistice on Nov. 11, the pandemic was already raging.

In fact, the second wave of the pandemic crept stealthily into Canada across the United States border on a fateful Friday the 13th in September 1918, gaining two lethal footholds here that day. Within days, it had made two further incursions, seeding infection from Ontario to Nova Scotia before mustering its strength and racing across Canada.

It arrived Sept. 13 at a military training camp in Niagara-on-the-Lake, Ont., along with Polish soldiers recruited in the United States and on their way to the French army.

The same day, Catholic clergy and parishioners from the United States reached Victoriaville, just east of Montreal, to attend a huge Eucharistic Congress over the weekend that was to draw more than 25,000 participants. By Monday, just hours after the Congress ended, priests and students at the Collège Sacré Coeur, a boarding school in Victoriaville that had been the site of some of the gatherings, were dead. Students still well enough to be sent home were dispatched across the province, viruses and all.

Four days later, the first flu-struck Canadian soldiers began reporting to the Station Hospital in St-Jean, Que., likely infected by recruits from Boston where the pandemic was in full, gruesome swing. From St-Jean, the virus swiftly made its way to Montreal, launching a cascade of death there. On Sunday, Sept. 22, the virus made landing in Sydney, N.S., along with 500 desperately ill American soldiers who had been trying to sail to France and had to go to shore for medical help.

From those four strategic landings, the second wave of the virus surged pitilessly across the country with easterners heading west by rail.

One prime disseminator of infection was the Canadian Siberian Expeditionary Force troops, who were headed to Russia to bolster Allied efforts on the Eastern Front. In late September, just two weeks after the virus arrived in Canada, SEF recruits left Sussex Camp in New Brunswick to travel by train to Vancouver, then across the sea to Russia. The same day, flu broke out at the camp. By the time their train hit Montreal, some soldiers were so ill they had to be hospitalized. It was the same story at stops in Winnipeg, Calgary and Vancouver.

“Like an invading army ravaging a foreign country, recruits from the Canadian Siberian Expeditionary Force spread disease to the towns they passed through on their way west,” writes Humphries.

On Wednesday, Oct. 2, just 19 days after it first hit Canadian soil in the east, the “Spanish Lady” reached the West Coast.

By mid-October, the pandemic was in full strength in Canada, as well as other parts of the world. Halifax had 500 cases by then, and Montreal, 20,000, according to front-page headlines in the Halifax Herald. Six hundred new cases emerged in Ottawa overnight. New York had seen more than 25,000 cases and Cape Town reported 140 burials in a single day.

Canadians scrambled to respond. There was no treatment. No cure. The invention of antibiotics to combat the deadly bacterial pneumonia that came in the flu’s wake was still more than a decade away. Even aspirin, that efficient queller of fevers, was uncommon. Vaccines were imperfectly understood and ineffective. It would be 15 years before virologists would isolate and culture any human flu virus in a lab, and even longer before they discovered how a virus could evolve to become so deadly.

People resorted to folk remedies and superstition. Some wore cotton bags filled with camphor or mothballs about the neck, reported journalist Eileen Pettigrew, who interviewed survivors and scoured newspaper reports for her 1983 book The Silent Enemy: Canada and the Deadly Flu of 1918.

“Some people put their faith in violet-leaf tea, goose-grease poultices, garlic buds, castor oil, salt water snuffed up the nose, or hot coals sprinkled with sulphur or brown sugar and carried through the house accompanied by clouds of billowing smoke,” she writes. First Nation remedies in Saskatchewan and Alberta included wild ginger and the barks of cottonwood, wild cranberry and poplar.

Some officials and individual citizens took action, closing schools, church services and theatres, and suspending public gatherings. In Halifax, for a short time the homes of sufferers were plastered with placards to warn of the flu lurking within. Priests in Montreal administered last rites on the streets and offered communion to citizens on their doorsteps, heralded by bugles or bells. Toronto hotels were pressed into duty as makeshift infirmaries. Calgarians had to wear face masks by law. Lethbridge, Alta., quarantined itself. Forty-five prairie towns along the Canadian Pacific Railway lines refused to allow trains to stop.

But in other places, officials turned a blind eye. On Oct. 5, T.J. Minnes, chairman of the board of health in Brantford, Ont., downplayed the ferocity of the virus, refused to implement the requests of the medical officer of health and, four days later, claimed the Spanish Influenza had bypassed his city. At the time, the hospital was turning away patients and a doctor had died. The following week, Brant­ford had 2,500 cases of flu and the medical officer of health had resigned in frustration.

Saskatoon’s medical officer of health, Arthur Wilson, was equally dismissive, saying the flu’s influence had been exaggerated by media reports — the 1918 version of “fake news.”

The military, more concerned with supporting the war effort, continued to encourage public events in Winnipeg to buoy war-weary spirits. Officers sent soldiers from the St-Jean barracks to Montreal for the funeral of Quebec’s lieutenant-governor even though the barracks were under quarantine.