PHILADELPHIA -- You've been warned against it, read about it, heard about it, seen your friends and family get it, maybe even received a shot to prevent it.
Every year, hundreds of millions of people around the world are affected by it. But have you ever wondered why the latest strain of flu is frequently identified as coming from the Far East or Southeast Asia? For example, the 1997-98 vaccine was designed to stop the Nanchang strain and the Harbin strain of flu. Both strains are named after cities in China.
According to Earl Henderson, Ph.D., professor of microbiology at Temple University School of Medicine, there are a variety of reasons the flu always seems to originate in that part of the world.
"The large population and crowded conditions in Asia, especially in China, make it a perfect place for new strains of the flu to arise," he says. "The flu needs a large population to exist due to its rapid spread and the protective immunity that develops in people. In addition, vaccinations against the flu are not very common in Asia."
Henderson cites another reason.
"People in Asia have a much closer relationship with animals than in other parts of the world. Ducks and swine, two animals that many Asians live in close contact with, are carriers of the flu. It's believed that new strains of the flu pass from these animals to humans as evidenced by last year's cases of 'bird flu.' "
According to Henderson, new strains of the flu take on the name of the city where they are first identified.
"There is constant surveillance going on by world health organizations," he says. "When a new strain of flu is identified, two things are analyzed: its potential to cause an epidemic and whether there's good chance a vaccine can be produced."
Although the flu kills less than one percent of the people who catch it, that small number translates into tens of thousands of deaths each year, says Henderson.
"Older adults and people who have existing medical conditions such as heart disease or respiratory problems are especially at risk," says Henderson. "Those are the people who should definitely receive a flu shot."
Although the flu has been around for thousands of year, says Henderson, it wasn't until fairly recently that it became a global problem.
"When Europeans first came to North America they inadvertently introduced the flu into the native-American population, a group of people who had no innate immunity to it," he says. "Tens of thousands of them died.
"The flu epidemic of 1918 and 1919 killed 20 million people around the world and was one of the first global epidemics," he says. "It's no coincidence that this epidemic coincided with World War I when massive numbers of people were moved around the world."
Henderson says that the rate of transmission is even greater today thanks to rapid global travel.
"A business traveler who picks up a case of the flu in China can be halfway around the world in a matter of hours," he says. "And in a blink of the eye, or cough, the flu is spread."
Materials provided by Temple University HSC. Note: Content may be edited for style and length.
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