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Flu Breakthrough: The Search for a Universal Vaccine

Tired of having to get a different flu shot -- or two -- every year? Someday one shot may protect us against all the strains.
WebMD Magazine - Feature

Medical sleuths have been trailing the elusive cold and flu viruses for more than a century. Now they finally might be onto something. A universal flu vaccine could be on the horizon -- and even more effective treatments for the common cold. Wayne Marasco, MD, PhD, is one of the most ardent sleuths. His perp -- the flu virus -- has caused the deaths of more than 36,000 Americans, and that’s just in one year.

Marasco is an associate professor of medicine at the Dana-Farber Cancer Institute and Harvard Medical School. His work means that a universal flu vaccine could be within reach -- one that would protect against all flu strains over a lifetime, just like existing vaccinations for diseases like measles and smallpox. Up to now, a universal flu vaccine has been elusive, because the virus's constant ability to change has made it a hard target to combat. "The virus undergoes a process we call antigenic drift, which means that it continuously evolves so that it escapes the immune system," he explains. "We've been kind of chasing our tails and immunizing every season to keep up with these variations."

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Even though only two different types of flu virus -- A and B -- are responsible for most human flu cases, each type has several subtypes, and the virus can change from season to season. That's why researchers can never seem to keep up.

The 1918 Flu Pandemic

Compounding the problem is that people are always on the move. Hundreds of years ago, Europeans first carried the flu to North America on ships, infecting Native Americans who had previously been flu-free. Today, air travel can speed flu viruses (including the H1N1, or swine, flu) around the world even faster. Last year swine flu was reported for the very first time among the Matsigenka tribe deep in the Amazon jungle, proving that no place is too remote to escape a flu bug.

Even before the age of commercial air travel, the flu virus was able to get around. In 1918, after the influenza A virus jumped from birds to humans, soldiers in World War I spread the disease as they moved around the European front. By the time the worldwide pandemic had ended a year later, a quarter of Americans had become sick and 50 million people worldwide had died from the illness, which was named the Spanish flu.

Researchers have since discovered one reason the 1918 flu strain was so lethal. Unlike most of today's flu viruses, which can only copy themselves in the upper respiratory system (mouth, nose, and throat), the Spanish flu was able to replicate inside the lungs. As infected peoples' lungs filled with fluid, they suffocated to death, sometimes within a day or two of showing symptoms. While the H1N1 swine flu virus is also able to directly infect the lungs, researchers note that so far it has not been nearly as deadly as the Spanish flu.

Recently, researchers have discovered something else about that 1918 strain -- it's the genetic granddaddy of the H1N1 flu strain that's making headlines today. They traced the 2009 H1N1 virus back to the 1918 Cedar Rapids Swine Show in Iowa, where many pigs developed a respiratory infection that looked an awful lot like the influenza virus that was spreading like wildfire among humans. Over the next 90 years, that virus swapped genes a few times with other flu viruses, and re-emerged as the H1N1 flu strain we're dealing with today. The H1N1  flu strain circulating now is nowhere near as lethal as its predecessor, but unlike the H1N1 flu, it tends to be more dangerous to young people, and researchers think they've figured out why. Older people (particularly those born before 1950) have been exposed to the swine flu's relatives, and their bodies have built up antibodies to the virus. Young people don't have that same immunity.  

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