The influenza outbreak of 1918–1919 carried off between 20 to 40 million people worldwide. The Spanish flu outbreak differed significantly from other influenza (flu) epidemics. It was much more lethal, and it killed a high proportion of otherwise healthy adults. Most flu outbreaks kill only the very young, the elderly, and people with weakened immune systems. Scientists and public health officials have been trying to learn more about Spanish flu in the hopes of preventing a similar outbreak.
The Spanish flu virus caused one of the worst pandemic of an infectious disease ever recorded. And while the threat of many infectious diseases, including tuberculosis and smallpox, have been contained by antibiotics and vaccination programs, influenza remains a difficult disease. There are worldwide outbreaks of influenza every year, and the flu typically reaches pandemic proportions (lethally afflicting an unusually high portion of the population) every 10–40 years. The last influenza pandemic was the Hong Kong flu of 1968–69, which caused 700,000 deaths worldwide, and killed 33,000 Americans. The influenza virus is highly mutable, so each year's flu outbreak presents the human body with a slightly different virus. Because of this, people do not build an immunity to influenza. Vaccines are successful in protecting people against influenza, but vaccine manufacturers must prepare a new batch each year, based on their best supposition of which particular virus will spread. Most influenza viruses originate in China, and doctors, scientists, and public health officials closely monitor flu cases there in order to make the appropriate vaccine. The two main organizations tracking influenza are the Centers for Disease Control (CDC) and the World Health Organization (WHO). The CDC and other government agencies have been preparing for a flu pandemic on the level of Spanish flu since the early 1990s.
Spanish flu did not originate in Spain, but presumably in Kansas, where the first case was recorded in March, 1918, at the army base Camp Funston. It quickly spread across the United States, and then to Europe with American soldiers who were fighting in the last months of World War I. Infected ships brought the outbreak to India, New Zealand, and Alaska. Spanish flu killed quickly. People often died within 48 hours of first feeling symptoms. The disease afflicted the lungs, and caused the tiny air sacs, called alveoli, to fill with fluid. Victims were soon starved of oxygen, and sometimes effectively drowned on the fluid clogging their lungs. Children and old people recovered from the Spanish flu at a much higher rate than young adults. In the United States, the death rate from Spanish flu was several times higher for men aged 25–29 than for men in their seventies.
Social conditions at the time probably contributed to the remarkable power of the disease. The flu struck just at the end of World War I, when thousands of soldiers were moving from America to Europe and across that continent. In a peaceful time, sick people may have gone home to bed, and thus passed the disease only to their immediate family. But in 1918, men with the virus were packed in already crowded hospitals and troop ships. The unrest and devastation left by the war probably hastened the spread of Spanish flu. So it is possible that if a similarly virulent virus were to arise again soon, it would not be quite as destructive.
Researchers are concerned about a return of Spanish flu because little is known about what made it so virulent. The flu virus was not isolated until 1933, and since then, there have been several efforts to collect and study the 1918 virus by exhuming graves in Alaska and Norway, where bodies were preserved in permanently frozen ground. In 1997, a Canadian researcher, Kirsty Duncan, was able to extract tissue samples from the corpses of seven miners who had died of Spanish flu in October 1918 and were buried in frozen ground on a tiny island off Norway. Duncan's work allowed scientists at several laboratories around the world to do genetic work on the Spanish flu virus. But by 2002, there was still no conclusive agreement on what was so different about the 1918 virus.
The influenza virus is believed to originate in migratory water fowl, particularly ducks. Ducks carry influenza viruses without becoming ill. They excrete the virus in their feces. When their feces collect in water, other animals can become infected. Domestic turkeys and chickens can easily become infected with influenza virus borne by wild ducks. But most avian (bird-borne) influenza does not pass to humans, or if it does, is not particularly virulent. But other mammals too can pick up influenza from either wild birds or domestic fowl. Whales , seals , ferrets, horses, and pigs are all susceptible to bird-borne viruses. When the virus moves between species , it may mutate. Human influenza viruses most likely pass from ducks to pigs to humans. The 1918 virus may have been a particularly unusual combination of avian and swine virus, to which humans were unusually vulnerable.
Enacting controls on pig and poultry farms may be an important way to prevent the rise of a new influenza pandemic. Some influenza researchers recommend that pigs and domestic ducks and chickens not be raised together. Separating pigs and fowl at live markets may also be a sensible precaution. With the concentration of poultry and pigs at huge "factory" farms, it is important for farmers, veterinarians, and public health officials to monitor for influenza. A flu outbreak among chickens in Hong Kong in 1997 eventually killed six people, but the epidemic was stopped by the quick slaughter of millions of chickens in the area. Any action to control flu of course must be an international effort, since the virus moves rapidly without respect to national borders.
[Angela Woodward ]
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