Spanish flu

The 1918–1920 influenza pandemic was a massive global health crisis.

It was caused by the H1N1 subtype of the influenza A virus. This virus spread across the entire world in a very short time. Experts estimate that nearly 500 million people were infected. This number represents about one third of the global population at that time. The death toll was also incredibly high. Estimates suggest between 17 million and 50 million people died. Some researchers believe the number could be as high as 100 million.

This makes it one of the deadliest pandemics in human history.

The mechanism of the pandemic was worsened by the conditions of World War I. Many people were living in crowded medical camps and military hospitals. These environments were ideal for a respiratory virus to move between hosts. Poor hygiene and malnourishment were also common due to the war. These factors often led to bacterial superinfection. This means that bacteria would infect a person after the virus had already made them sick. Most victims died after a long and difficult struggle. The virus was also known for causing a specific symptom called cyanosis. This caused a blue-violet or "dusky" color on the faces of dying patients.

There are several theories about where the virus first appeared. Because historical data is limited, the exact origin remains indeterminate. Some historians point to Haskell County, Kansas, in the United States. They note documented cases there in March 1918. However, a 2018 study suggested these cases were actually milder than those in New York City. Other researchers look toward Europe as a possible source. Virologist John Oxford suggested the Étaples camp in France might be a center. This camp was very crowded and had many pigs and poultry nearby. He theorized a precursor virus might have moved from birds to pigs and then to humans.

The pandemic is often called the "Spanish flu," but this name is misleading. During the war, many countries used wartime censors to suppress bad news. They did this to maintain high morale among their citizens and soldiers. Spain was a neutral country and did not have these same censorship rules. Consequently, Spanish newspapers reported the outbreak freely and openly. This created a false impression that Spain was the epicenter of the disease.

A Spanish official even protested this name in a letter to medical journals. He noted that the epidemic was not born in Spain. This misunderstanding led to many different names used around the world.

Different cultures gave the disease many unique and descriptive names. In Japan, some people called it the "sumo flu." In Senegal, it was referred to as the "Brazilian flu." In parts of Africa, some called it a "white man's sickness." In Poland, it was known as the "Bolshevik disease." Some people in Freetown suggested calling it "manhu," a Hebrew word meaning "what is it?"

These names are often called exonyms. An exonym is a name used by one group for something outside their own group. These names often reflected geopolitical tensions or social boundaries of the time.

One of the most unusual aspects of this pandemic was its mortality pattern. Most influenza outbreaks primarily kill the very young and the very old. This pandemic was different because it had unusually high mortality among young adults.

This was a very surprising and devastating trend for society. Scientists have offered several reasons for this high death rate in healthy adults. One theory involves a six-year climate anomaly. This anomaly may have affected how disease vectors migrated through bodies of water. However, the claim that young adults suffered more is still a subject of debate among researchers.

Today, the way we talk about this event has changed to be more accurate. The World Health Organization now provides best practices to prevent social stigma. They advise against using culturally significant names for new diseases. Because of this, many historians now prefer the term "1918–1920 influenza pandemic."

This avoids the unfair labels associated with the name "Spanish flu." Understanding this pandemic helps scientists prepare for future respiratory outbreaks. It also shows how social and political conditions can change the course of a biological event.