Related topics: •  Flu (Influenza)

During three decades in the 20th century, a deadly strain of flu spread across the globe, killing anywhere from hundreds of thousands to tens of millions of people. It's been nearly 40 years since the last global outbreak. According to some experts, the world is overdue for another.

Nobody knows when the next widespread bird flu outbreak will strike, but some researchers believe an epidemic may already be in motion. A new type of flu virus has emerged in Asia, and it's a far cry from the typical flu bug that circulates through the United States every winter. Called bird flu, or avian flu, it's an example of a strain of the flu virus called influenza A -- a virus that has jumped from one species (birds) to another (us, and a few other unlucky hosts, including a group of tigers in a zoo).

By June 2007, the bird flu had killed 191 people and millions of domesticated birds in more than 50 countries, such as Denmark, Greece, Thailand, and Iran. Although the human toll has been small so far, an official with the World Health Organization told the Associated Press in 2005, "The world is now in the greatest possible danger of a pandemic."

Should you be worried about bird flu? What are the real risks, and what can be done about it? Read on to find out more about this emerging disease.

Federal health agencies put it simply: Bird flu is an infection caused by avian (bird) viruses. Wild birds around the globe carry these viruses in their intestines, but are rarely sickened by them. For domestic birds like chicken, turkeys, and ducks, however, bird flu can be a killer.

Just like humans, birds can come down with the flu. The illness varies widely in intensity, from mild to deadly. A particularly vicious flu virus hit domestic chickens and ducks in several Asian countries in late 2003 and early 2004. Millions of birds have either died from the flu or had to be destroyed to stop the spread of the disease.

Because many families in many parts of the world keep small flocks of chickens and ducks, the outbreak has been both an economic disaster and a threat to human health.

Realizing the fears of health officials and scientists, the virus has now spread outside Asia. The World Health Organization reported 317 cases in humans by June 2007, including outbreaks in Egypt, Azerbaijan, Turkey, and Iraq.

Some symptoms of bird flu in humans are similar to those caused by typical flu: fever, cough, sore throat, and muscle aches. Other symptoms include eye infections, pneumonia, severe respiratory diseases, and life-threatening conditions such as acute respiratory distress.

The virus is found in the saliva, nasal discharge, and feces of infected birds. Most cases in humans seem to have resulted from contact with infected poultry or surfaces contaminated by bird feces. It's also possible for the virus to spread by drinking contaminated water and getting contaminated bird secretions or feces in your eyes or nose, either from touching them or breathing in contaminated particles.

Bird flu has two of the key qualities of a global threat: It's both deadly and (among birds) extremely common. Despite concerted efforts to quell it, it's still showing up in poultry. It also spreads faster and more widely than any previous bird flu outbreak, and it can be deadly. The only thing keeping it in check at the moment is that it doesn't spread easily from birds to humans or from humans to humans. Although there have been a few documented instances of transmissions occurring between family members in Indonesia and Thailand, confirmed cases of people catching the bird flu from another person are extremely rare.

Unfortunately, flu viruses have a way of finding new victims. If a bird flu virus mingles with one of the human flu virus strains, the two viruses could swap genetic material. In theory, the bird flu could pick up genes that make it as contagious as a strain of flu bug that strikes seasonally. One other way the virus could become more likely to infect people could be through gradual genetic changes over time. The virus has shown that it can infect animals that usually do not get the flu, such as cats. In 2004, 147 tigers at a single zoo in Thailand were killed after 45 died and the rest developed severe cases of bird flu, presumably after eating infected chickens.

If the virus does start spreading quickly to people, it could turn into a major killer. Humans have very little natural immunity to the bird flu. To make matters worse, viral resistance may render two common antiviral flu medications -- amantadine and rimantidine -- ineffective against the bird flu. Two other medications, oseltamavir and zanamavir, may still be effective against bird flu in its present form, according to the Centers for Disease Control and Prevention

So far Americans are at low risk from the bird flu outbreak, according to the CDC. The strain of virus causing the bird flu (highly pathogenic H5N1) hasn't been found in the United States. Migrating birds are being monitored for the H5N1 virus and public health workers are keeping a close watch on travelers from affected countries, however.

Bird flu has become so entrenched in Asia that it may never disappear. At this point, experts can only hope to contain it and, if possible, prevent a human epidemic. Asian countries are searching for outbreaks of bird flu in chickens and ducks and are destroying any affected flocks. But because many of the outbreaks occur on small family farms scattered throughout the countryside, not all outbreaks are reported or discovered by authorities, according to the World Health Organization.

In the United States, health officials are aggressively putting together pandemic bird flu prevention measures. In April 2007, the Food and Drug Administration (FDA) approved the first US vaccine against bird flu. While there have not yet been any reported cases of bird flu in the United States, if there ever is, the vaccine could provide limited early protection against widespread infection. Having a vaccine readily available in case there is an outbreak will buy time for health officials who could then develop a vaccine tailor-made to the specific strain of bird flu that develops in the United States. “The approval of this vaccine is an important step forward in our protection against a pandemic,” says FDA Commissioner Andrew C. von Eschenbach, MD.

The bird flu vaccine, derived from a human strain of the virus, immunizes adults 18- to 64-years-old and will be available to those who are at increased risk of exposure to bird flu. The vaccine will not be available commercially, but the federal government has already purchased it as part of the US Strategic National Stockpile and will distribute it as needed.

If the virus ever did start rapidly spreading to humans, the vaccine against the flu would be the first line of defense. However, if the virus started to spread tomorrow, it could take several months to make a vaccine that is effective for the particular pandemic flu strain that develops and for it to be in wide distribution. Health experts hope that a pandemic, should one occur, will hold off long enough to give them time to test and stockpile new vaccines.

Meanwhile, the CDC is training state laboratories in molecular techniques to identify H5N1 viruses, working with the World Health Organization to investigate the bird flu virus in Vietnam, doing lab testing of H5N1 viruses, and planning new vaccines.

Since bird flu is limited to Asia, parts of Europe, the eastern Mediterranean, and Africa, there's no reason to take extra precautions in other places. At this point, the World Health Organization has not yet advised travelers to avoid any countries because of bird flu.

But if you do travel to any of the 58 countries that has reported a bird flu outbreak in poultry or wild birds (including Thailand, Japan, Korea, India, Nigeria, Russia, and Zimbabwe), avoid poultry farms, contact with animals in live food markets, or surfaces that appear to be contaminated by feces from poultry or other animals. The CDC also advises travelers to clean their hands frequently with soap and water or an alcohol-based hand cleaner. In addition, travelers to affected countries should only eat poultry products -- such as chicken or eggs -- that have been thoroughly cooked. Heat destroys influenza virus.

If bird flu does become a global epidemic, use tried-and-true strategies for staying healthy during flu season: Wash your hands regularly, cover your mouth when you cough, stay away from large crowds, and get vaccinated if you can. If you can’t stay away from large crowds, consider the use of a face mask. This time, you could lose more than a few days of work.

-- Chris Woolston, MS, is a health and medical writer with a master's degree in biology, and the co-author of Generation Extra Large: Rescuing Our Children from the Epidemic of Obesity (Perseus paperback, 2006). A contributing editor at Consumer Health Interactive, he earlier worked as a staff writer at Hippocrates, a national magazine for physicians. He has also covered science issues for Time Inc. Health, WebMD, and the Chronicle of Higher Education. His reporting on occupational health earned him an award from the Northern California Society of Professional Journalists.

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First published March 30, 2005
Last updated November 20, 2007
Copyright © 2005 Consumer Health Interactive

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