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Scientists Discover New Key to Flu Tansmission
The scientists found that a flu virus must be able to attach itself to an umbrella-shaped receptor coating human respiratory cells before it can infect cells in the upper airways.
"What the lock needs is the right key. It opens the door," said Ram Sasisekharan, a professor of biological engineering and health sciences at Massachusetts Institute of Technology in Cambridge.
The H5N1 avian flu virus now almost exclusively infects birds. But it can occasionally pass to a person.(..)
Before a flu virus can enter a human respiratory cell, a protein on the surface of the virus must bind with chains of sugars called glycans that sit on the outside of the cells.
Scientists have classified these chains according to how they are linked together chemically. In birds, the virus binds with alpha 2-3 receptors; in humans, it binds with alpha 2-6 receptors.
To infect humans, scientists thought the H5N1 bird flu virus would need to simply mutate so it could bind with alpha 2-6 receptors. But it turns out not all alpha 2-6 receptors are the same. Some are short and cone-shaped and some are long and umbrella-shaped.
Shape difference may explain why humans can get bird flu from a bird and not pass it along easily to other humans, he said.
So far, the bird flu virus has found a way to bind only to the cone-shaped structures in human upper airways. The virus has already killed 216 people and infected 348 people in 14 countries, according to the World Health Organization.
But the study found that the most infectious human flu viruses bind with the umbrella-shaped receptors in the upper respiratory tract. The researchers believe the H5N1 bird flu virus would need to adapt so it could latch on to these umbrella-shaped receptors before it could be spread readily from human to human.
Comment: Now these scientists have found out how to manipulate the virus making it able to jump from human to human. The darned thing just wouldn't do it before, but now they have it figured out.
And, of course, then they will be able to give us all of the vaccines that they have been trying to stick us with. They'll get this pandemic thing off the ground one way or another.