Spanish flu: 100 years onThe global flu pandemic: 100 years later

Published 3 January 2018

Called “La grippe,” “three-day fever” and the “Spanish flu,” the influenza pandemic of 1918–1919 ravaged communities worldwide, claiming the lives of an estimated 25 million to 50 million people. In the United States, more than 25 percent of the population was affected by the extremely virulent influenza A H1N1 virus, forcing schools, theaters and public places to close. Nearly 100 years later, the threat of another influenza pandemic looms large as the scientific and global health communities find ways to prepare for, and battle, future outbreaks.

Called “La grippe,” “three-day fever” and the “Spanish flu,” the influenza pandemic of 1918–1919 ravaged communities worldwide, claiming the lives of an estimated 25 million to 50 million people. In the United States, more than 25 percent of the population was affected by the extremely virulent influenza A H1N1 virus, forcing schools, theaters and public places to close. Americans were ordered to wear masks to try to slow the spread of the disease, which often progressed rapidly — sometimes in as little as two days — to a lethal form of pneumonia. USC Keck Medicine says that nearly 100 years later, the threat of another influenza pandemic looms large as the scientific and global health communities find ways to prepare for, and battle, future outbreaks.

A monster virus emerges every several decades
Brad Spellberg, MD, is an expert in infectious disease and a 2017–18 American Association for the Advancement of Science (AAAS) Public Engagement Fellow. He is the chief medical officer at Los Angeles County + USC Medical Center and professor of clinical medicine at the Keck School of Medicine of USC.

Spellberg said:

Not only is another influenza pandemic possible, but it’s certain to eventually happen. Influenza mutates annually — we call that ‘antigenic drift.’ That low, constant rate of mutation, however, isn’t really the problem when it comes to pandemics. The real problem that leads to a pandemic is a major ‘antigenic shift,’ which takes place when several different viruses infect the same cell and recombine, creating a Frankenstein-like virus that’s very different from viruses that have recently circulated. These major antigenic shifts occur every several decades. When these shifts happen, people have no memory immunity to the new virus, meaning that their immune systems aren’t able to react swiftly to fight it.

With the 1918–1919 flu season, older patients had some memory immunity to the virus because a similar strain had circulated years before. Younger patients, who didn’t have that memory immunity, fared much worse. About half of the people who died from the Spanish flu were between the ages of 20 and 40.