How does bird flu affect other species? UI professor explains
URBANA, Ill. (WCIA) — Ever since a rare human case emerged in Texas last month, talk of the H5N1 virus — also known as bird flu — has been spreading around almost as much as the virus has. But why does the bird flu affect more than just birds?
An expert from the University of Illinois has provided a few answers.
Dr. James Lowe, a professor of veterinary clinical medicine, said the H5N1 virus mostly impacts farm animals — usually birds and cows. It can pass around as one bird ingests the fecal matter of another infected bird. Currently, experts don’t have a solid explanation as to how it passes from birds to mammals or how it can transmit between cows, but the working theory is that it’s the result of cows getting exposed to infected birds in some way.
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Marine mammals like seals and sea lions can be affected by the bird flu as well. Lowe said the exact mortality rate is unknown since no one knows how many total marine mammals have been infected, but thousands of them have died with H5N1 infection.
The case in Texas was the first report of the virus passing from birds to cows, then a cow to a person. But do humans have a reason to worry?
Lowe said not really, adding that humans were exposed to bird flu in chickens for a couple of years and yet hardly any human cases occurred. He also said there’s some evidence that exposure to other flu viruses or vaccines can allow for better immunity.
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While a person getting the bird flu is a very unlikely event, that’s not to say it’s impossible. H5N1 was first detected in China in 2006, and since then, two human cases have been reported in the United States. The virus usually spreads after prolonged close contact with an infected person or animal, and is often short-lived.
If any symptoms at all, H5N1 infections can lead to mild respiratory and gastrointestinal issues, as well as conjunctivitis in humans. For those with weaker immune systems, infection may cause more severe respiratory issues and even death — but Lowe said this result is extremely rare.
That result isn’t so rare for animals, however, depending on the strain. Highly pathogenic strains of H5N1 can kill poultry and some wild birds. Low pathogenic strains are often not deadly.
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The virus can also affect species in different ways. In marine mammals and carnivorous animals, infection can cause neurological rather than respiratory issues, leading to severe disease and high death rate. The case is much less extreme for many cows, whose infection may be undetectable or cause only mild illness.
Lowe said these differences depend on where the virus interacts with specific entry points on the surfaces of cells, called sialic acid receptors. Different species have a great amount of these receptors in different places. For marine and carnivorous mammals, H5N1 can link with the brain’s SA receptors and cause dangerous disease. For humans, the lungs provide the most ripe conditions for SA receptors to bond with the virus, leading to respiratory problems or even pneumonia. For cows, receptors are more common in other parts of the body.
The Centers for Disease Control and Prevention says public health risk is currently low for the H5N1 virus, but they are monitoring the situation carefully. To see updates and find more information on avian influenza, visit their website.
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