Influenza pandemic of 1918
Pandemics are epidemics that occur on a global scale. They generally result from the emergence of an influenza A virus that is novel for the humanpopulation. The hallmark of pandemic influenza is excess mortality--the number of deaths observed during an epidemic of influenza-like illness in excess of the number expected. During this century, pandemics occurred in 1918, 1957(Asian flu), and 1968 (Hong Kong flu). The 1918 influenza outbreak is regarded as the worst in human history--it killed up to 40 million people world wide.
The outbreak started in the United States at an army base in the Midwest andthen spread to Europe and other parts of the world. This epidemic was different from most others because it preyed heavily upon the 20 to 40 year old agegroup, which was normally the most healthy and resistant to disease.
It all started on March 11, 1918 at an army camp in Kansas. A company cook named Albert Mitchell reported to the infirmary with typical flu-like symptoms--a low grade fever, mild sore throat, a light headache, and muscle aches. Bed rest was recommended. By noon, 107 soldiers were sick. Within2 days, 522 people were sick. Many were gravely ill with severe pneumonia. Then reports started coming in from other military bases around the country. Thousands of soldiers docked off the East Coast were sick. Within a week, the influenza was hitting isolated places, such as the island of Alcatraz. Every state in the United States had been infected. The death toll in United Stateswas 850,000 people. The actual killer was the pneumonia that accompanied theinfection.
A subset of patients died extremely quickly, within two or three days of symptoms. Massive amounts of fluid accumulated in the lungs of these people; in asense these patients drowned. Other people died of secondary infections withbacterial pneumonia. Antibiotics did not exist in 1918 and hence there was no way to treat those secondary infections.
In order to curtail the spread of the disease, the Health Department adoptedmany measures. Theaters, lodges, dance halls, and places of amusement were closed for several weeks. Fresh air and adequate heat were counseled. People were advised to get 9 hours of sleep. Smoking was prohibited on streetcars in order to prevent spitting.
The infection, which was airborne, spread across the Atlantic. By April, French troops and civilians were infected. By mid-April, the disease had spread to China and Japan. By May, the virus had spread throughout Africa and South America. 60% of the Eskimo population was wiped out in Alaska. 80 to 90% of the Samoan population was infected. In the end, 25 million people had died. Some estimates put that number as high as 37 million. 18 months after the disease appeared, the flu bug vanished and has never shown up again. Even with a death toll of 850,000, the United States was the area that was the least devastated by the virus.
No one at the time was really sure what had happened. Viruses were not knownthen. However, while conducting autopsies in 1918, some army doctors had preserved specimens in formaldehyde. One of these jars contained the lungs of a 21 year old soldier that died on September 26, 1918. The researchers at ArmedForces Institute of Pathology in Washington, D.C., managed to isolate geneticmaterial from the virus and were successful in gathering a wealth of information.
The virus had apparently passed from birds to pigs and then to humans. Viruses tend to remain stable in birds, but occasionally when they infect pigs, thepig's immune system kicks into action and produces antibodies. In order to survive, the virus is forced to mutate. And it was this mutated swine virus that caused the most deadly pandemic on Earth.
At present a lot of work is being done to figure out whether there is a genetic basis for why this particular virus was so virulent. Influenza viruses often mutate and new strains arise continually, which is why vaccines have to bemade every year to match the current strain. It is possible that such a pandemic could occur again. If scientists are able to unravel the mystery of howthe genetic structure of the virus is related to its lethal ability, future epidemics could perhaps be prevented.