Scientist Johan Hultin traveled to Brevig Mission, Alaska, a town of a few hundred souls in the summer of 1997. He was searching for buried bodies, and Alaska’s frozen ground was the perfect place to find them. Digging through the permafrost—with permission from the town’s authorities—he eventually uncovered a woman who died almost 80 years previously and was in a state of excellent preservation. Hultin then extracted samples of the woman’s lung before reinterring her. He intended to use this to decode the genetic sequence of the virus that had killed this Inuit woman along with 90 percent of the town’s population.

Brevig Mission was just one place that was part of a global tragedy, one of the worst ever to befall humanity: the influenza pandemic of 1918-19. The outbreak of this influenza virus, also known as Spanish flu, spread with astonishing speed around the world, overwhelming India, and reaching Australia and the remote Pacific islands. In just 18 months at least a third of the world’s population was infected. Estimates on the exact number of fatalities vary wildly, from 20 million to 50 million to 100 million deaths. If the upper end of that estimate is accurate, the 1918 pandemic killed more people than both World Wars put together. (Get the facts on influenza.)

View Images The first official cases of the 1918 Spanish flu pandemic were recorded at the U.S. Army’s Camp Funston, Kansas, where this emergency influenza ward held treated patients. SPL/AGE FOTOSTOCK

War and pestilence

Several closely related viruses cause influenza, but one strain (type A) is linked to deadly epidemics. The 1918-19 pandemic was caused by an influenza A virus known as H1N1. Despite becoming known as the Spanish flu, the first recorded cases were in the United States in the final year of World War I. (Explore the memorials of World War I.)

View Images A magnified view of the H1N1 virus responsible for the 1918 pandemic. SPL/AGE FOTOSTOCK

By March 1918 the United States had been at war with Germany and the Central Powers for 11 months. During that time America’s small, prewar army had grown into a vast fighting force that would eventually send more than two million men to Europe. (How the United States entered World War I.)

American forts experienced a massive expansion as the entire nation mobilized for war. One of these was Fort Riley, Kansas, where a new training facility, Camp Funston, was built to house some of the 50,000 men who would be inducted into the Army. It was here in early March that a feverish soldier reported to the infirmary. Within a few hours more than a hundred other soldiers had come down with a similar condition, and more would fall ill over the following weeks. In April more American troops arrived in Europe and brought the virus with them. The first wave of the pandemic had arrived. (What is the difference between an epidemic and a pandemic?)

Deadly speed

The Spanish flu strain killed its victims with a swiftness never seen before. In the United States stories abounded of people waking up sick and dying on their way to work. The symptoms were gruesome: Sufferers would develop a fever and become short of breath. Lack of oxygen meant their faces appeared tinged with blue. Hemorrhages filled the lungs with blood and caused catastrophic vomiting and nosebleeds, with victims drowning in their own fluids. Unlike so many strains of influenza before it, Spanish flu attacked not only the very young and the very old, but also healthy adults between the ages of 20 and 40.

View Images Biologists at St. Bartholomew’s Hospital in London are analyzing brain and lung tissue from victims of the 1918 pandemic as part of global efforts to understand the virus. Here, wax-mounted tissue samples sit on a list of children’s names who fell victims to influenza in 1918. SPL/AGE FOOTSTOCK

The principal factor in the virus’s spread was, of course, the international conflict then in its last phase. Epidemiologists still dispute the exact origins of the virus, but there is some consensus it was the result of a genetic mutation that perhaps took place in China. But what is clear is that the new strain went global thanks to the massive and rapid movement of troops around the world.

The drama of the war also served to obscure the unusually high mortality rates of the new virus. At this early stage, the illness was not well understood and deaths were often attributed to pneumonia. Strict wartime censorship meant that the European and North American press were unable to report outbreaks. Only in neutral Spain could the press speak freely about what was happening, and it was from this media coverage that the disease took its nickname.

The second wave

The overcrowded trenches and encampments of the First World War became the perfect hosts for the disease. As troops moved, so the infection traveled with them. The wave that had first appeared in Kansas abated after a few weeks, but this was only a temporary reprieve. By September 1918 the epidemic was ready to enter its most lethal phase.

It has been calculated that the 13 weeks between September and December 1918 constituted the most intense period, taking the greatest number of lives. At least 195,000 Americans died in October alone. In comparison, total American military casualties for the whole of World War I came in at just over 116,000. Once again, it was the crowded military encampments where the second wave initially gained a hold. In September an outbreak of 6,674 cases was reported at Camp Devens, a military base in Massachusetts.

As the crisis reached its zenith, the medical services began to be overwhelmed. Morticians and gravediggers struggled, and conducting individual funerals became impossible. Many of the dead ended up in mass graves. The end of 1918 brought a hiatus in the spread of the illness and January 1919 saw the beginning of the third and final phase. By then the disease was a much diminished force. The ferocity of the autumn and winter of the previous year was not repeated and mortality rates fell.

Although the final wave was much less lethal than its predecessors, it was still able to wreak considerable damage. Australia, which had quickly enacted quarantine restrictions, managed to escape the worst of the flu until the beginning of 1919, when the disease finally arrived and took the lives of several thousand Australians.

View Images The Spanish flu did not strike in Australia until 1919. Quarantine camps like this one, in Wallangarra, Queensland, were set up to treat and contain the illness. PAUL FEARN/ALAMY/ACI

The general trend of mortality, however, was downward. There were cases of deaths from influenza—possibly a different strain—as late as 1920, but by the summer of 1919 health care policies and the natural genetic mutation of the virus brought the epidemic to a close. Even so, its effects, for those left bereaved or suffering long-term health complications, were to last decades.

Lasting impact

The pandemic left almost no part of the world untouched. In Great Britain 228,000 people died. The United States lost as many as 675,000 people, Japan some 400,000. The south Pacific island of Western Samoa (modern-day Samoa) lost one-fifth of its population. Researchers estimate that in India alone, fatalities totaled between 12 and 17 million. Exact data in the number of deaths is elusive, but global mortality figures are estimated to have been between 10 and 20 percent of those who were infected.