H5N1’s lethal effect unveiled

Scientists claim to have discovered why the avian flu virus, H5N1, is so lethal.

When comparing Vietnamese patients infected with H5N1 with a group infected with two types of human flu virus, researchers found that there were much higher levels of viral load in the H5N1 patients.

Menno de Jong and colleagues believe that their findings support the view that the H5N1 virus replicates to much higher levels than the human flu virus and that high levels of the virus result in an overwhelming inflammatory response that contributes to lung dysfunction and eventual death.

They also argue that their findings suggest that it is important to diagnose H5N1 infection early and to administer antivirals quickly ? preventing it from replicating and causing intense inflammation.

Published in the October issue of the journal Nature Medicine, the study found that the patients with H5N1 infection had much higher levels of viral load in the throat than patients with human virus.

Patients with H5N1 who died had the highest markers of viral load in the throat and in their blood.

High levels of the virus triggered a release of some inflammatory cytokines (compounds which function in inter-cell communication); levels of these cytokines correlated with levels of viral load and were highest in the patients who died.

A loss of lymphocytes (white blood cells involved in the immune system) in the peripheral blood was associated with fatal H5N1 infection.

The authors reported in the study: “Our observations point to a central role for high viral burden in the pathogenesis [causes] of human H5N1 disease and suggest that timely suppression of viral replication should remain the mainstay for treatment of influenza H5N1.

“The focus of clinical management should be on preventing the intense cytokine response by early diagnosis and effective antiviral treatment.”

More than 130 people have been killed in six countries across the world by the H5N1 strain of avian flu after they came into contact with infected birds. Experts fear that the rapid spread of the disease could prompt a global flu pandemic if the virus mutates so that it is more easily transferable between humans.