"Chinese flu": be careful, but don't panic
Avian flu is transmitted in contact
The first detailed study of the H7N9 influenza virus is published in ScienceNadezhda Markina, Newspaper.
A group of Chinese and Canadian experts studied the transmission between mammals of the H7N9 avian influenza virus, the one from which 130 people fell ill in China, 36 of whom died. Doctors fear that the virus may lead to a new pandemic, although so far the necessary condition for this – direct transmission of the virus from person to person – has not been recorded. All the patients had contact with poultry.
The study was conducted in China, at Shantou University, with the participation of specialists from the University Health Network, which includes several medical institutions. His results are published urgently on Friday in the journal Science (Zhu et al., Infectivity, Transmission, and Pathology of Human H7N9 Influenza in Ferrets and Pigs).
"This work was done specifically to find clues to the transmission of the virus affecting people in China," said David Kelvin, the study leader, a professor at the Public Research University in Toronto. "She showed that the H7N9 virus in its existing form can be transmitted between mammals through close contact, but cannot effectively spread through the air."
To study the ways of transmission of the virus, scientists set up a very simple experiment on ferrets. Ferrets were previously chosen by researchers as the optimal model of influenza virus transmission in the mammalian population, it was proved that its results can be extrapolated to humans.
Ferrets were infected with a virus isolated from the blood of people who died from the "bird flu" caused by the H7N9 virus. A suspension of the virus was dropped into the nose of six ferrets. The next day, three healthy ferrets were placed in one cage with infected animals, and the other three healthy ferrets were put in another cage nearby. As a result, all the animals sitting with the carriers of the infection picked up the virus, and among the three ferrets in another cage, one was infected. The researchers found the virus in the nasal secretions of ferrets about a day before the animals showed obvious signs of the disease. By the way, all ferrets were moderately ill: it was limited to snot, sneezing, coughing and general lethargy, but none died or became seriously ill.
From this simple experiment, despite the obviously insufficient statistics, scientists have drawn certain conclusions. Firstly, the H7N9 virus is effectively transmitted between mammals, and therefore between humans, with close contact and much weaker through the air. Secondly, if a person has no obvious symptoms of the disease, this does not mean that he is not infected.
"Our results indicate that the risk of infection is high for medical professionals who are in close contact with patients," Kelvin emphasizes. – As for the transmission of the virus by air, then, as shown by the animal model, it is unlikely. The same applies to people."
Scientists analyzed the organs of infected ferrets and found viral RNA in the upper and lower respiratory tracts, as well as in the lymph nodes and brain.
At the next stage, the H7N9 virus was tested on pigs. Experts believe that in natural conditions pigs serve as a reservoir for mixing different strains of the mammalian and avian influenza virus and as a result, the avian virus acquires the ability to infect humans. The new strain resulting from this combination may have pandemic potential. However, in this experiment, pigs that scientists infected with the H7N9 virus, unlike ferrets, did not transmit it to healthy animals either through the air or through close contact.
Recall that the H7N9 influenza virus, which was isolated from the body of sick people in China, received such a name by the type of the main antigens – viral envelope proteins, hemagglutinin type 7 and neuraminidase type 9.
Portal "Eternal youth" http://vechnayamolodost.ru24.05.2013