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Influenza Virus of 1918 Lethal in Primates

Influenza Virus of 1918 Lethal in Primates

NEW YORK (Reuters Health) Jan 17 - In a new study, researchers show that the influenza virus responsible for the 1918 influenza pandemic is highly lethal in a macaque model of infection. The findings, reported in the January 18th issue of Nature, suggest that it is the virus' ability to induce an aberrant immune response in the host that made it so pathogenic.

Approximately 50 million deaths occurred as a result of the 1918 influenza outbreak. In recent years, several reports have documented the extreme virulence of the 1918 strain in mice. However, the strain's pathogenic potential in primates was unclear.

Dr. Yoshihiro Kawaoka, from the University of Wisconsin at Madison, and colleagues constructed genes for the 1918 virus from published sequences and generated virus using reverse genetics.

In a cynomolgus macaque model, the researchers found, the 1918 influenza virus causes a severe respiratory tract infection, resulting in respiratory distress syndrome and death. By contrast, animals infected with a conventional human virus (H1N1) had only mild symptoms.

Further analysis indicated an aberrant immune response in the 1918 virus-infected animals, which provided inadequate protection against the pathogen. The researchers believe that this played a key role in the lethality of the virus.

"The ability of influenza viruses to modulate host immune responses, such as that demonstrated for the avian H5N1 influenza viruses, may be a feature shared by the virulent influenza viruses," the authors conclude.

Nature 2007;445:319-323.


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