August 2, 2018

One hundred years ago, in 1918, the Spanish flu began taking its deadly toll around the world. The Spanish flu was the worst outbreak of influenza, or flu, in history. Medical historians estimate that from 1918 through 1919, the Spanish flu killed at least 600,000 people in the United States and 20 million to 50 million people worldwide. The Spanish flu was the first and most severe of three pandemics (worldwide occurrences) of influenza in the 1900’s. Less severe pandemics occurred in 1957 and in 1968.

The Camp Jackson Base Hospital in South Carolina is filled with Spanish flu patients in the fall of 1918. Credit: Otis Historical Archives/National Museum of Health and Medicine

The Spanish flu struck in the final year of World War I (1914-1918), while many European nations were concentrating on war efforts. Many soldiers died of influenza, and troop concentrations and movements helped spread the disease. Most countries at war did not publicly acknowledge the number of deaths from influenza because of strict wartime censorship. The pandemic became known as the Spanish flu because the disease was widely reported in Spain, which remained neutral during the war.

Spanish flu caused symptoms similar to other influenza infections, including fever, chills, headaches, body aches, and fatigue. However, many people suffering from Spanish flu quickly developed severe pneumonia (inflammation of the lungs) and pulmonary edema (excess fluid accumulation in the lungs), causing victims to suffocate. Unlike other varieties of influenza, which most seriously affect infants and the elderly, the Spanish flu killed mainly young, healthy adults between 20 and about 40 years of age.

Medical historians believe the virus that caused Spanish flu, like many strains of influenza virus, probably originated in Asia. However, the first reported outbreaks of the disease occurred in the United States. The disease quickly spread to Europe, Asia, Africa, and South America. During the height of the pandemic, the huge number of deaths severely disrupted many societies. Many countries tried various public health measures to contain the pandemic. In the United States, several cities closed schools, churches, theaters, and other public gathering places. By the end of 1919, the pandemic had largely ended.

Scientists have long sought to discover why the particular variety of influenza that caused the Spanish flu was so deadly and spread so quickly. In the 1990’s, they identified preserved lung tissue of victims of the disease that still contained the genetic information from the Spanish flu virus. They confirmed it as a variety of H1N1, one of several types of influenza viruses that can infect both people and certain animals, such as swine. Scientists believe birds are the original source of the Spanish flu and other pandemic influenza viruses. Birds carry many varieties of influenza viruses and in rare occasions transmit these viruses to human beings. In 2005, scientists re-created the Spanish flu virus through a process called reverse genetics. By studying the virus, they hope to discover why the disease spread so quickly and why it was so deadly. In addition, scientists can study the Spanish flu virus to develop new vaccines and treatments to prevent or contain future influenza outbreaks.

June 16, 2014

In a series of controversial experiments, scientists at the University of Wisconsin in Madison have re-created in a laboratory a strain of influenza virus that closely resembles the virus responsible for the Spanish flu pandemic (global occurrence) of 1918 that killed over 50 million people worldwide. The scientists contend that they re-created the deadly virus as a necessary step to help combat future flu pandemics. However, critics of the research argued that the experiments should be halted immediately as they pose a great threat to public safety.

Influenza tends to occur in widespread epidemics that occur most every year. Each outbreak is caused by a virus slightly different from earlier ones. Some strains (types) cause mild or moderate illness, and others cause many deaths. The Spanish flu of 1918 was the deadliest outbreak of influenza in history. Medical historians believe the Spanish flu virus, like many strains of influenza, probably originated in Asia. The disease quickly spread to the United States, Europe, Africa, and South America. During the height of the pandemic, the huge number of deaths severely disrupted many societies. Less severe pandemics occurred in 1957 and in 1968 but still resulted in many deaths.

Influenza viruses (shown here are greatly magnified and artificially colored) may cause flu when they are inhaled. (© Linda Stannard, UCT/SPL from Photo Researchers)

The Wisconsin scientists, led by Yoshihiro Kawaoka, isolated several genes from influenza viruses that normally infect wild ducks in Asia. These “avian influenza” (also known as “bird flu) viruses often mutate so they can infect mammals, including humans, and spread in global pandemics. Using a technique known as “reverse genetics,” the scientists used the individual genes to reconstruct an entire flu virus. They compared this rebuilt virus to virus samples from frozen corpses of victims of the 1918 Spanish flu pandemic recovered in Alaska. The rebuilt virus was 97 percent identical to the deadly Spanish flu virus.

The scientists infected ferrets with the re-created virus so they could study how it infected and spread among mammals. Kawaoka contends that such experiments are important so scientists can understand why the 1918 Spanish flu virus was so lethal, compared to other strains of flu that originate in wild birds. For example, the scientists identified a mutation in the rebuilt virus that enabled it to spread more easily from one animal to another. Scientists argue that continued research will help them better understand how the virus infects animals and makes them ill. This information will be useful for developing effective vaccines and treatments to combat future flu pandemics.

Other scientists argue that the research is too dangerous to continue and that another Spanish flu pandemic is unlikely to occur naturally. They claim that the most serious risk lies with the rebuilt virus being released from the high-security laboratory through some accident. Should an infected research animal escape, the deadly virus could spread rapidly in a new global pandemic with catastrophic results. The United States National Institutes of Health (NIH) which funds the controversial research, insisted that proper safety measures are being taken and that funding for the research would continue.

Additional World Book articles:

• SARS
• Swine flu
• Influenza: A New Threat from an Old Foe (a Special Report)
• Medicine in the 21st Century: The Promise of Genetics (a Special Report)