Scientists identify why bird flu virus is so deadly

  • November 14, 2005

    LONDON (Agence de Presse Medicale for Reuters Health) - Scientists said on Friday they may have identified one of the reasons why the bird flu virus H5N1 is so deadly to humans – it triggers far worse inflammation in the lungs than do human flu viruses.

    In a study published in Respiratory Research, researchers report that in human cells, the virus can trigger levels of inflammatory proteins more than 10 times higher than caused by the human flu virus H1N1.

    “This might contribute to the unusual severity of the disease caused by H5N1 in humans, which can escalate into life-threatening pneumonia and acute respiratory distress,” they said in a statement.

    Dr. Michael Chan and colleagues from the University of Hong Kong and collaborators in Vietnam, studied the levels cytokines and chemokines induced by the virus H5N1 in human lung cells, in vitro.

    The authors compared protein levels induced by strains of H5N1 that appeared in Hong Kong in 1997 (H5N1/97) and Vietnam in 2004 (H5N1/04), with levels induced by the human H1N1.

    Their results show that H5N1 is a much more potent inducer of pro-inflammatory proteins than H1N1.

    Twenty-four hours after infection with H5N1/04, the levels of the chemokine IP-10 in bronchial epithelial cells reach 2200 pg/mL, whereas in cells infected with H1N1 they only reach 200pg/mL. In H5N1/97-infected cells, IP-10 levels reach 1750 pg/mL. Similar results were found for other chemokines and cytokines.

    “We suggest that this hyper-induction of cytokines may be relevant to the pathogenesis of human H5N1 disease,” the researchers concluded.

    Respir Res, 2005.

    • note
      i wonder if steroid use might mitigate this problem (i.e. prednisone, dexamethasone or fluticasone or budesinide).  Afterall - we use these in asthmatics with lung inflammation as well as in PCP pneumonia, so why not in this scenario?

  • Is the steroid an immune suppresent?

  • CC… can you translate that out of doctor-speak?

  • Sorry all - stupid jargon . . .

    Basically the same things that result in asthma exacerbations (i.e. that cause worse asthma symptoms) are the things found to increase so dramatically in the bird flu virus.
    When people with asthma are exposed to certain “triggers” - molds, dust, pollen, cats, cigarette smoke, etc. they may experience a sudden worsening of symptoms.  This is because “inflammatory mediators” - i.e. chemicals which are supposed to protect us from disease - increase pathologically.  This causes the airways to become smaller and for mucus secretion which causes the airflow to slow considerably.  This is asthma in a nutshell.
    With the bird-flu virus, many of these inflammatory mediators are increased dramatically as well.  This may result in severe respiratory symptoms as the airways narrow causing difficulty in breathing. 
    This is why i considered that steroids might be useful here as - yes Mary - they are immune suppressants. 
    I hope that this clears up the fog, and again my apologies.

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