The current 2019-2020 flu season is on track to be one of the worst in a decade. According to the CDC, between 19-26 million people have caught the flu since October and between 10,000-25,000 people have died. But as bad as the seasonal flu is this year, it pales in comparison to some of the biggest flu pandemics in history.
This is largely because we have a much better scientific understanding of flu viruses, improved hygiene standards and flu vaccines, which, while never 100% effective, are powerful defenses to help protect people from getting sick.
However, even after the invention of the vaccine, pandemics still happen because flu viruses evolve very quickly. Here are five of the largest epidemics in recent history:
The "Russian Flu" Epidemic of 1889
Known as the “Russian Flu,” this influenza outbreak is believed to have begun in St. Petersburg but it soon spread across Europe and the world. It was one of the first epidemics that was covered regularly by the developing daily press. Newspapers wrote about the local spread of the disease and also discussed the situation in other distant European cities thanks to telegraph reports. It is estimated that around 1 million people died of the Russian Flu.
The 1918-19 “Spanish Flu” Pandemic
Known at the time as the “Spanish Flu,” this flu pandemic was the most severe pandemic in recorded history. It was caused by an H1N1 virus. According to the CDC, an estimated 500 million people — or 1/3rd of the world’s population — caught the virus during the pandemic and between 50 million and 100 million people were killed. 675,000 died in the United States alone. Some victims died within mere hours or days of developing symptoms.
The pandemic was so far reaching in part because of World War I troop movement. There were also no vaccines stop the spread of the virus at the time, no antiviral medications to help treat it, and no antibiotics to treat secondary bacterial infections that can come with the flu. All that people could do to contain the spread of the disease was wash their hands, avoid public gatherings and quarantine the sick.
The 1957-58 "Asian Flu" Pandemic
First reported in Singapore in February 1957, a new influenza A (H2N2) virus emerged and became known as the “Asian flu.” It spread throughout China and its surrounding regions first, and it arrived in the US by that summer.
Approximately 1.1 million people died worldwide, according to the CDC; of those deaths, 116,000 were in the US. Most of the cases affected young children, the elderly and pregnant women. While deadly, the death rate in this pandemic was relatively contained because a vaccine was rapidly developed and made available. There were also antibiotics available to treat secondary infections.
The 1968 “Hong Kong Flu” Pandemic
An Influenza A virus (H3N2) outbreak in China led to the flu pandemic of 1968, also known as the “Hong Kong Flu.” It started in 1968 and lasted until 1969-70. The virus responsible for the pandemic is believed to have evolved from the strain of influenza that caused the 1957 pandemic through “antigenic shift” — an abrupt, major change in the virus that results in new surface proteins, creating a virus subtype that humans have little or no immunity to because the body doesn’t recognize its surface proteins.
According to the CDC, approximately 1 million people around the world died from this pandemic, and 100,000 of those deaths occurred in the United States.
The 2009 H1N1 Pandemic
In 2009, a new kind of influenza A (H1N1) virus emerged in the United States and spread quickly around the world. Initially known as “swine flu,” this particular subtype of virus contained a novel combination of influenza genes that hadn’t previously been identified in animals or people. The virus was designated as (H1N1)pdm09.
Very few young people had any existing immunity to the virus, but about 1/3rd of people over 60 had antibodies against it. Because it was very different than other H1N1 viruses, the seasonal vaccinations didn’t offer much cross-protection either. When a vaccine was finally made, it was not available in large quantities until late November, after the illness had already peaked.
The CDC estimates that between 151,700 - 575,400 people died worldwide during the first year that the (H1N1)pdm09 virus circulated. About 80% of those deaths are believed to have been people younger than 65 — which is unusual. During typical seasonal influenza epidemics, 70-90% of deaths occur in people over 65.
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