context: Web MD has been in touch with the CDC, the World Health Organization, and infectious disease experts to answer your bird fluquestions. Bird flu, or avian influenza, is a viral infection spread from bird to bird. Currently, a particularly deadly strain of bird flu -- H5 N1 -- continues to spread among poultry in Egypt and in certain parts of Asia. Technically, H5 N1 is a highly pathogenic avian influenza ( HPAI) virus. It's deadly to most birds. And it's deadly to humans and to other mammals that catch the virus from birds. Since the first human case in 1997, H5 N1 has killed nearly 60% of the people who have been infected. But unlike human flu bugs, H5 N1 bird flu does not spread easily from person to person. The very few cases of human-to-human transmission have been among people with exceptionally close contact, such as a mother who caught the virus while caring for her sick infant. Migrating water fowl -- most notably wild ducks -- are the natural carriers of bird flu viruses. It's suspected that infection can spread from wild fowl to domestic poultry. Because the disease has spread to wild birds, pigs, and even to donkeys, it will be difficult, if not impossible, to eradicate. As of 2011, the disease was well established in six nations: Bangladesh, China, Egypt, India, Indonesia, and Vietnam. People catch bird flu by close contact with birds or bird droppings. Exactly what "close contact" means differs from culture to culture. Some people have caught H5 N1 from cleaning or plucking infected birds. In China, there have been reports of infection via inhalation of aerosolized materials in live bird markets. It's also possible that some people were infected after swimming or bathing in water contaminated with the droppings of infected birds. And some infections have occurred in people who handle fighting cocks. People don't catch the virus from eating fully cooked chicken or eggs. There have been a few cases where one infected person caught the bird flu virus from another person -- but only after close personal contact. So far, there has been no sustained human-to-human spread of H5 N1. As long as the bird flu virus doesn't change into a human flu virus, it won't spread far in people. But sometimes -- after close personal contact -- a person who gets bird flu does infect another person. In Indonesia in 2006, bird flu spread to eight members of one family. Seven of them died. It's not clear exactly how this happened. Family members likely had similar contacts with infected birds. They may also have shared genes that made them particularly susceptible to the virus. However, casual contact does not seem to be involved. During the fall of 2011, researchers from Erasmus Medical Center in the Netherlands made a stunning announcement. They had taught H5 N1 the nasty trick of going airborne and spreading among ferrets. Why ferrets? Nearly all human flu bugs spread easily among ferrets. They are commonly used in studies of human flu viruses. " The virus is transmitted as efficiently as seasonal flu," lead researcher Ron Fouchier, Ph D, told New Scientist magazine. At the University of Wisconsin, a team led by virologist Yoshihiro Kawaoka, Ph D, DVM, also created an H5 N1 mutant that spreads among mammals. Both research teams were funded by the U. S. National Institute of Health. In a statement, the NIH says the research shows "that the H5 N1 virus has greater potential than previously believed to gain a dangerous capacity to be transmitted among mammals, including perhaps humans." The NIH funded the research because it felt there was a need for more information on how H5 N1 might learn to spread among humans. The U. S. National Science Advisory Board for Biosecurity asked the study authors not to publish crucial information about the creation of the mutant viruses. The details will be made available only to qualified researchers. But the studies remain extremely controversial. Some senior scientists have said the mutant viruses should never have been created. They note that while the mutant viruses are housed in state-of-the-art containment facilities, the risk of escape is not zero. It's also not unprecedented. In 1977, an extinct H1 N1 flu bug re-emerged along the Russia/ China border. This so-called " Russian flu" led to widespread epidemics. Although officials denied it, many scientists believe the virus had escaped from a laboratory. The H5 N1 virus found in a wild bird in Washington state in late 2014 is slightly different from the Asian-origin avian H5 N1 virus that made humans sick. Various strains of bird flu pop up in U. S. poultry from time to time. When they do, all affected poultry flocks are culled. For example, in 2004 a highly dangerous bird flu strain appeared in a Texas chicken flock. The outbreak involved an H5 N2 virus (not the H5 N1 bird flu). By April 2004, the outbreak had been eradicated. No human infections were detected. While no human cases of bird flu have been seen in the U. S. or North America, the CDC is asking people who have traveled to East Asia to see a doctor if they develop flu-like symptoms. If so, it's important to tell the doctor about having visited these areas so the proper tests can be done. Bird flu symptoms in people can vary. Symptoms may start out as normal flu-like symptoms. This can worsen to become a severe respiratory disease that can be fatal. In February 2005, researchers in Vietnam reported human cases of bird flu in which the virus infected the brain and digestive tract of two children. Both died. These cases make it clear that bird flu in humans may not always look like typical cases of flu. If a person -- or a susceptible animal -- gets infected with bird flu and human flu at the same time, the bird and human flu viruses could swap genes. Even without swapping genes, H5 N1 could mutate into a form that more easily infects humans. The lab-created H5 N1 mutants remain in high-security labs. But the mutations needed to make H5 N1 an airborne, human virus already exist in H5 N1 viruses seen in nature. So far, the full set of mutations has not appeared in the same virus. It would be bad news if H5 N1 were to become as contagious as human flu. If it remained as lethal as it is now, the fatality rate would be about 60%. The deadliest flu bug in history, which caused the 1918 Great Pandemic, had a fatality rate of 2%. Even if it's a relatively mild new flu virus, it could spread rapidly across the globe. That's because most humans would have no immunity to the new kind of flu. During the 20th century, this happened three times. But just because it happened before doesn't mean it will happen this time. While experts say it's inevitable that sooner or later we'll see another flu pandemic, it's by no means certain that the current bird flu virus will be the cause. Even if a new human flu emerges, public health officials might be able to contain it. H5 N1 is susceptible to the newer flu drugs. And a vaccine already has been created and stockpiled by the World Health Organization. Yes. On April 17, 2007, the FDA announced its approval of the first vaccine to prevent human infection with one strain of the bird flu. The vaccine has been purchased by the U. S. federal government to be distributed by public health officials if needed. This vaccine will not be made commercially available to the general public. Other bird flu vaccines are being developed by other companies. And the World Health Organization has a stockpile of the vaccine, with plans to quickly produce more if needed. When given along with immunity-boosting agents called adjuvants, experimental H5 N1 vaccines offer good cross-protection against different H5 N1 variants. And several companies are working on universal flu vaccines and antivirals that would protect against all known strains of influenza. The flu drugs oseltamivir ( Tamiflu), zanamivir ( Relenza), or peramivir ( Rapivab) should work against bird flu, although more studies are needed. These drugs must be given soon after symptoms appear. Unfortunately, H5 N1 in humans can be a severe illness requiring hospitalization, isolation, and intensive care.