1918 Influenza Pandemic (Spanish Flu)

What is the Spanish flu (1918 influenza pandemic)?

The influenza pandemic of 1918 (commonly called the “Spanish flu”) was an outbreak of illness around the world caused by a version of the flu virus. Millions of people died and millions more were infected.

The pandemic started in 1918 and had three waves — or spikes in illness — in the spring, fall and winter. The fall wave was the deadliest. Some experts think there could’ve been a fourth wave, as well, in 1920. More people between the ages of 20 and 40 died than expected, compared to seasonal flu and other illnesses (where people in this age group usually are less likely to get seriously ill). Scientists are still studying why that might’ve been.

How many people got the flu during the 1918 pandemic?

Experts estimate that 500 million people — or a third of the world’s population at the time — were infected with the flu during the 1918 pandemic.

How many people died during the 1918 pandemic (Spanish flu)?

About 50 million people worldwide died from the flu between 1918 and 1919. Some experts estimate the number to be as high as 100 million. About 675,000 people died in the U.S.

Why was the 1918 pandemic so deadly?

Many different factors may have played a part in the high number of deaths from the 1918 pandemic, including:

War-time conditions

Many people lived in crowded conditions with limited ways to keep germs from spreading. The desire to keep morale high during war meant that governments censored information about the flu.

Limited healthcare options

There were limited medical services available due to doctors and nurses serving in the war. Intensive care units and life support machines (like ventilators) didn’t exist in the form they do now. There weren’t any antiviral medications to treat influenza — and medical professionals didn’t even know that influenza was caused by a virus yet.

Lung damage and bacterial infections

The virus caused lung damage, allowing bacterial infections to develop. These bacterial infections were a common cause of death. Antibiotics weren’t available to treat infections at that time.

Immune factors

There are some theories that younger adults (those in their 20s and 30s) died at a higher rate during the pandemic because they hadn’t been exposed to that version of flu virus before. This meant they didn’t have immunity (tools their body could use to fight the infection, like antibodies) to that particular virus. Other theories suggest that their immune systems overreacted to the virus (cytokine storm), damaging healthy tissues in the process.

What does the Spanish flu do to you?

Many flu symptoms that people experienced in 1918 were similar to what we experience with seasonal flu now. But many cases were more severe. Symptoms included:

• A sudden, and sometimes very high, fever.
• Dry cough.
• Headache and body aches.
• Shortness of breath.
• Sore throat.
• Chills.
• Runny nose.
• Loss of appetite.
• Extreme weakness.
• Extreme tiredness (fatigue).
• Blue skin, lips or nails (cyanosis).
• Pulmonary edema.
• Internal bleeding.

What caused the 1918 influenza pandemic (Spanish flu)?

The 1918 flu pandemic was caused by a form of influenza A virus (H1N1). Experts think it might have started as an avian influenza. Researchers think the first cases in humans started in early 1918, possibly in military camps in the U.S.

Can people still get Spanish flu?

People can still get different versions of influenza virus that caused the 1918 pandemic. In fact, most flu viruses today are descended from (started from) the virus that caused the pandemic.

There are different types of flu virus — A, B and C. Additionally, viruses have different subtypes and variations. We’re all now more likely to have been exposed to types of influenza A similar to the one circulating in 1918, giving us some immunity. This means flu viruses are less likely to start a pandemic as large as the one that happened in 1918 — unless they change (mutate) a lot from the flu viruses that we’ve been exposed to.

Influenza epidemics and pandemics, like the H1N1 pandemic in 2009 (“swine flu”), happen when a flu virus mutates in such a way that most people don’t have immunity and get severely ill.

Why was it called the Spanish flu?

People called the influenza that caused the 1918 pandemic the “Spanish flu” because they (mistakenly) thought it started in Spain. In reality, the first cases are thought to have been in the U.S. — Spain was just the first country to start talking about it publicly. The U.S. — and other countries involved in World War I — censored news of the illness, worrying that it would hurt morale. Spain wasn’t involved in the war and didn’t censor its news.

The World Health Organization (WHO) recommends avoiding using geographic terms in names for illnesses. In this case, the term “Spanish flu” could be seen as blaming a particular country for an illness and creating a stigma.

How was the pandemic of 1918 different from COVID?

The pandemic of 1918 and the COVID-19 pandemic were caused by different viruses. A version of influenza A caused the 1918 pandemic. The COVID-19 pandemic, which started late in 2019, was caused by a new type of coronavirus. In both cases, people had little or no immunity to the viruses yet.

During both pandemics (and others in history), public health officials put measures in place to try to prevent the spread. These included:

• Closing schools.
• Banning public gatherings.
• Requiring protective gear, like masks and gloves.
• Requiring people to isolate or quarantine.