Friday, May 05, 2006

It's in the blood

The least surprising thing about H5N1 is that it continues to surprise. The latest is in a Letter in the journal Emerging Infectious Diseases showing the presence of H5N1 virus in the blood stream of a 5 year old Thai boy from last December that ended fatally. Influenza virus has been detected in blood only rarely. On the other hand H5N1 has also attacked multiple organ systems, so it was getting around the body somehow. The EID communication suggests bloodborne spread is on the list of possibilities. Since viral presence in the blood is not routinely examined, this may be more common than previously assumed.

An article by the excellent flu reporter Helen Branswell discusses whether this has implications for the safety and integrity of the blood supply in the setting of a pandemic, or even a more limited outbreak.
Canadian Blood Services and the American Red Cross have been studying the issue, but currently it is believed that the risk is more theoretical than real, because influenza's incubation period is so short. Once people develop symptoms they would be unlikely to want to give blood and would probably be turned away if they showed up to a blood-donor clinic.

"From the blood-donor and blood-supply point of view, the issue would be whether there's virus in the blood before the patient becomes ill,” said Dr. Jeffrey McCullough, who holds an American Red Cross professorship in transfusion medicine at the University of Minnesota.

“Once you've got somebody that's sick, of course, they wouldn't be acceptable as a blood donor,” he said. (Branswell, Canadian Press)
To these ears there is an element of "whistling past the graveyard" in this response. And what about people who are asymptomatically infected?

The Letter writers also raise the question of precautions in the hospital or elsewhere.
Because probable H5N1 avian influenza transmission among humans has been reported, this case should be a reminder of the necessity to carefully handle and transport serum or plasma samples suspected to be infected with H5N1 avian influenza. Because viable virus has been detected in blood samples, handling, transportation, and testing of blood samples should be performed in a biosafety (category III) containment laboratory to prevent the spread of the virus to healthcare and laboratory workers. (EID, cites omitted)
Probably it makes sense for all bodily secretions to be treated as infectious in these settings.

What a difficult and dangerous virus this is.