Prolonged Shedding of Swine Flu Virus

[indigo girl]

Here is another influenza mystery story. We get to know a little more about what influenza can do, but don't know what it means.

The virology laboratory in Bordeaux in the southwest of France tested via RT-PCR over 1200 nasopharyngeal swabs between May 1 and the first week in October and found 186 positive for the new pandemic strain. They looked at five of these cases more closely, monitoring them for duration of viral shedding. Two of the five kept shedding for 2 to 4 weeks (paper in Eurosurveillance by Fleury et al., v. 14, #49, December 10, 2009).

These patients were treated intensively with the antiviral neuriminidase inhibitors but had prolonged viral shedding, although both did well clinically. The viral isolates were checked for the main mutation that confers resistance (H274Y) and neither had it. The virus was apparently sensitive to the drugs. So there was no apparent explanation for why these patients continued to shed virus for much longer than the usually claimed period of 5 to 7 days from onset. This was despite the use of antivirals which in experimental challenge studies with human volunteers have cut the length of viral shedding in half (a median of 107 hours to 58 hours). Prolonged viral shedding can occur in children and the immunocompromised, but that describes neither of these patients.

It may be that people can continue to harbor infection and even shed virus to some extent, but not enough to infect others. It's another of the many things we don't know about flu. But now we know that prolonged shedding of virus can and does occur. We just don't know what it means.

Follow the link below for the case histories of these patients:

http://scienceblogs.com/effectmeasure/2009/12/prolonged_shedding_of_swine_fl.php

The Editors of Effect Measure are senior public health scientists and practitioners. Paul Revere was a member of the first local Board of Health in the United States (Boston, 1799). The Editors sign their posts "Revere" to recognize the public service of a professional forerunner better known for other things.

[oramar]

Viral equivalents of Typhoid Mary. If I were a person studying this I would not be to quick to say these people are not contageous. Don't forget flu outbreaks disappear and return and no one has fully explained how. It could be that these low level infections could go on for long periods of time eventually infecting someone who is extremely sensitive. That person then becomes the super spreader that starts the new outbreak.