The new strain of avian influenza has some genetic traits that make it potentially a very easily transmissable disease. The warning has come from scientists who have studied the other avian flu, H5N1, a now prevalent strain of the virus.
The H7N9 is a new virus. It is not, as many think, an established strain that has suddenly become capable of trasmission and has in its primitive form crossed the zoonotic barrier. It is a recombinant strain, that shows the merging of different strains and therefore it has acquired all of the characteristics of the merged genetic material.
And some of the genetic traits of the merger, so to speak, have marked capabilities of transmission from bird to mammals, and a very important mutation, which was also the hallmark of H5N1, and that is the ability to latch on to special cell in the respiratory tract which can make the infection much more difficult to treat.
Furthermore, Fouchier, a professor at the Erasmus center in Holland, adds that "the virus doesn't look like a bird virus anymore; it looks like a mammalian virus."
The Chinese authorities so far have been diligent in the laboratory follow up and examination of the specimens they have received, although they are being critized for their tardiness in reporting cases that go back as far as February, raising suspicions that it knew something was afoot long before the news spread.
Fouchier was the author of a study published last year that showed how the H5N1 had undergone 5 genetic mutations that made it airborne in ferrets, the mammals whose immune response is closest to that exhibited by human beings.
One of the mutations was in an enzyme called polymerase, another in the hemagglutinin protein that 'coats' the surface of the virus. What is more worrisome, H7N9 has undergone both those mutations too.
Fouchier cautions that this is a virus that warrants deep scrutiny and alertness, but also confirms that just like H5N1, the virus might never acquire the level of virality that could result in a deadly pandemic like the Spanish Influenza. In fact H5N1 has been circulating for 16 with just such genetic mutations without having acquired human to human transmissibility.
One of the steps that the Chinese authorities are recommended to follow is to measure the antibody response of people who have been exposed to the victims of the virus infected so far. This might give clues to how many people have actually been infected, and who are, so far, asymptomatic.
That is also important because an epidemic, although slow at its onset and with few numbers to show, can evolve quickly and grow exponentially in a very short time.
The other characteristic of the H7N9 strain is that it is not highly pathogenic in birds, so that the infected birds might not show any symptoms and not give clues to their infection.
Another important step is to test the virus on ferrets to ascertain the response in those mammals.
Source: France 24/ 4.7.13
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