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Ten years ago the headlines blazed "Killer Bird Flu!" but the feared virus never reached American shores. Now avian influenza is killing millions in the Midwest of the USA, but all of the victims are birds, at least so far.

Bird flu news has largely disappeared from public awareness in the USA. The Asian H5N1 influenza virus, which killed 440 of the 826 people who have contracted it since 2003, is no longer a public health concern. An offspring of the H5N1 virus with genes from milder forms of bird flu, however, has killed 20,000,000 chickens and turkeys in just three states, Iowa, Minnesota, and Wisconsin since the beginning of 2015. Poultry workers are being required to wear protective suits and are being asked to take Tamiflu, a medication designed to forestall the earliest symptoms of flu.

Nobody knows how lethal the latest flu virus is to humans, but because it can wipe out entire flocks of poultry in just two days, it is assumed to be dangerous.

Basic Bird Flu Facts

The new avian influenza viruses are in the H5N1, H5N8, and H5N2 categories. The "H" and the "N" in the name of a flu virus refer to the antigens they produce, the particles they emit that interact with the human immune system. There are 17 different H antigens and nine different N antigens.

H5N1 is the bird flu virus that caused an epidemic in 2009. It had become much less lethal, which enables it to travel much more widely. Exceptionally lethal viruses tend to kill off their hosts before they can infect others. There is a vaccine for H5N1.

H5N8 is another virus that can infect both birds and people. Its symptoms are usually "flu like" in people. It just causes sniffles, mild coughing, headaches, and a low fever.

H5N2 is the main virus spreading through the Midwest now. It is not known to cause symptoms in humans. It affects many different kinds of birds, usually causing only mild symptoms. However, some strains of H5N2, like those now epidemic in the Midwest, can kill commercial poultry en masse.

There is a flu vaccine for birds. It's used in China to protect flocks of chickens, ducks, and geese. However, there is no vaccine for H5N8 and H5N2 for people that covers the strains going around in the US right now.

How Is Bird Flu Spread?

It is important to understand that the current outbreak of bird flu is an epidemic (regional outbreak), not a pandemic (global outbreak), and it is currently limited to birds. However, the US government is sufficiently concerned that H5N2 could become a permanent problemin the United States that it has assigned 365 US Food and Agriculture Department workers to controlling the infection's spread.

Bird flu is spread when birds (or people) come in contact with the droppings, saliva, or nasal secretions of infected birds. The virus can also linger on the surfaces of cages. People can contract the virus when they handle dead birds, sick birds, bird manures, or when they prepare birds to be eaten.

See Also: Bird Flu in the News Again: Is a Springtime Epidemic Possible?

It takes more than casual contact for humans to come down with bird flu. Usually repeated exposure to large numbers of dead birds or large amounts of poultry manure is required. Human-to-human transmission of the disease, at least in its current form, has never been reported.

Continue reading after recommendations

  • P.J. Huffstutter and Julie Steenhuysen. Increased Human Protections Offered as H5N2 Outbreak Spreads. Reuters Health. 27 April 2015.
  • Julie Steenhuysen and Meredith Davis. Risk Low for Human Infection From U.S. Strains of Bird Flu -CDC. Reuter's Health. 23 April 2015.'Mind map by
  • Photo courtesy of photologic via Flickr:

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