Live Bird Flu Virus Found In Victim's Blood

TORONTO: Live H5N1 avian flu virus can be isolated in the blood of its victims, a finding that will be reported by Thai researchers in an upcoming issue of a scientific journal.

Evidence that H5N1 can spread via the bloodstream to parts of the body not normally attacked by the influenza viruses confirms this particular flu strain poses special challenges for both patient treatment and infection control, experts say. It also raises theoretical questions about the safety of the donated blood system should H5N1 trigger a pandemic.

"This is the first report of a high amount of (H5N1) virus in blood in human," University of Ottawa virologist Earl Brown said of the findings, outlined in a letter slated for publication in the June issue of Emerging Infectious Diseases.

"That's a bit surprising because blood is poisonous to flu virus. If you take any blood… and add it to flu, you kill it (the virus). This showed that the virus was living in the blood," said Dr. Brown, who was not an author of the letter.

While some types of viruses spread well in blood, cases of viremia (viral infection in the bloodstream) have only rarely been reported with influenza.

The researchers, from Chulalongkorn University, Srinakharinwirot University and the National Institute of Animal Health, all in Bangkok, reported on the case of a five-year-old Thai boy who died of H5N1 infection Dec. 7.

A blood sample drawn on the day he died contained high levels of live virus.

The finding helps to explain reports that some humans with H5N1 experience what is called systemic infection, with the flu virus spreading beyond its normal home in the respiratory tract to organs that would typically go untouched by human flu viruses.

Other research groups have reported finding traces of H5N1's RNA in blood. Those findings were highly suggestive that the virus was using the bloodstream to disseminate throughout the body, but were not strong enough evidence to rule out that spread was actually occurring via other routes such as the lymphatic system.

Reseachers at Oxford University's clinical research unit at the Hospital for Tropical Medicine in Ho Chi Minh City in Vietnam for instance, reported last year on a boy whose H5N1 infection spread to his brain, causing encephalitis.

The lead author of that report, virologist Menno de Jong, said his group has found viral RNA in the blood of about half of the H5N1 patients in which they've looked for it.

That poses challenges for treating patients infected with H5N1 because if the virus is spreading through the blood, so too must drugs that aim to combat the infection.

Currently there are only four flu antivirals on the market and one, zanamivir (sold as Relenza) is administered to the respiratory tract by inhalation. The drug would need to be formulated in an injectable form to be useful for systemic infection, Dr. de Jong said.

It also raises concerns about infection control for healthcare workers and laboratory scientists coming in contact with the blood of H5N1 patients, although precautions against contact with blood are widespread as a consequence of years of experience with blood-borne infections like HIV and hepatitis C.

"I think for this kind of flu, infection control measures should include all bodily secretions, basically," Dr. de Jong said.

The finding also raises questions about whether blood transfusions could be a source of infection if H5N1 were to become a pandemic strain.

rense.com 5/05/06