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  • Study challenges notion of 'pandemic' flu

    Source: http://web.mit.edu/newsoffice/2008/pandemic-0411.html

    Study challenges notion of 'pandemic' flu
    CDC-labeled pandemics no deadlier than seasonal influenza

    April 11, 2008

    The widespread assumption that pandemic influenza is an exceptionally deadly form of seasonal, or nonpandemic, flu is hard to support, according to a new study in the May issue of the American Journal of Public Health.

    The study challenges common beliefs about the flu--in particular the Centers for Disease Control and Prevention (CDC) claim that "the hallmark of pandemic influenza is excess mortality."

    Peter Doshi, a graduate student in the History, Anthropology, and Science, Technology and Society Program at MIT, based his study on an analysis of more than a century of influenza mortality data. He found that the peak monthly death rates in the 1957-1958 and 1968-1969 pandemic seasons were no higher than--and were sometimes exceeded by--those for severe nonpandemic seasons.

    Doshi says the pandemic-equals-extreme-mortality concept appears to be a generalization of a single data point: the 1918 season, a period in which "doctors lacked intensive care units, respirators, antiviral agents and antibiotics." He argues that "had no other aspect of modern medicine but antibiotics been available in 1918, there seems good reason to believe that the severity of this pandemic would have been far reduced."

    As may be expected given improvements in living conditions, nutrition and other public health measures, influenza death rates substantially declined across the 20th century. Doshi calculates an 18-fold decrease in influenza deaths between the 1940s and 1990s, a trend that began far before the introduction of widespread vaccination.

    Noting the gap between evidence and fear, Doshi identifies possible reasons that pandemic flu might be so misunderstood, including the possibility that commercial interests may be playing a role in inflating the perceived impact of pandemics. With public policies such as universal vaccination being discussed and more than $5 billion of federal money spent on preparing for the next pandemic, the study raises many important questions of public policy.

    "Should the trends observed over the 20th century continue to hold in the 21st, the next influenza pandemic may be far from a catastrophic event," he concludes.

  • #2
    Re: Study challenges notion of 'pandemic' flu

    American Journal of Public Health, 10.2105/AJPH.2007.119933

    Trends in Recorded Influenza Mortality: United States, 1900?2004
    Peter Doshi 1*
    1 Massachusetts Institute of Technology
    * To whom correspondence should be addressed. E-mail: pnd@mit.edu.

    Abstract
    Objectives. I sought to describe trends in historical influenza mortality data in the United States since 1900 and compare pandemic with nonpandemic influenza seasons.
    Methods. I compiled a database of monthly influenza-classed death rates from official US mortality tables for the years 1900 to 2004 (1905?1909 excluded), from which I calculated adjusted influenza season (July 1?June 30) mortality rates.
    Results. An overall and substantial decline in influenza-classed mortality was observed during the 20th century, from an average seasonal rate of 10.2 deaths per 100 000 population in the 1940s to 0.56 per 100 000 by the 1990s. The 1918 to 1919 pandemic stands out as an exceptional outlier. The 1957 to 1958 and 1968 to 1969 influenza pandemic seasons, by contrast, displayed substantial overlap in both degree of mortality and timing compared with nonpandemic seasons.
    Conclusions. The considerable similarity in mortality seen in pandemic and nonpandemic influenza seasons challenges common beliefs about the severity of pandemic influenza. The historical decline in influenza-classed mortality rates suggests that public health and ecological factors may play a role in influenza mortality risk. Nevertheless, the actual number of influenza-attributable deaths remains in doubt.
    Key Words: Epidemiology, Immunization/Vaccines, Infections, Public Health Practice, Mortality, Statistics/Evaluation/Research


    Access to complete article requires a fee or subscription.
    http://novel-infectious-diseases.blogspot.com/

    Comment


    • #3
      Re: Study challenges notion of 'pandemic' flu

      American Journal of Public Health, 10.2105/AJPH.2007.119933

      Trends in Recorded Influenza Mortality: United States, 1900–2004

      Peter Doshi 1*
      ---------------------------------------------------------------------

      Critique --
      <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p>
      By definition, an epidemic is a regionally localized event, while a pandemic is a worldwide event. Doshi is not studying mortality rates of worldwide pandemics but is simply taking a localized epidemic perspective on <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" /><st1:place w:st="on"><st1:country-region w:st="on">United States</st1:country-region></st1:place> influenza mortality data from 1900 to 2004. He also chooses to restrictively define a pandemic as an influenza outbreak with "excess mortality".
      <o:p></o:p>
      As readers of FluTrackers know there are other metrics to identifying a pandemic beyond excess mortality. For example, from WHO....<o:p></o:p>
      "A pandemic can start when three conditions have been met: a new influenza virus subtype emerges; it infects humans, causing serious illness; and it spreads easily and sustainably among humans." <o:p></o:p>
      <o:p></o:p>
      Note that the WHO definition of a pandemic does not require "excess mortality" as a necessary or sufficient condition for a pandemic. Using a restrictive definition of a pandemic based on "excess mortality", Doshi can claim that 1957 and 1968 don't meet his definition of a pandemic -- but only for the United States because he doesn't study worldwide mortality rates during these periods.
      <o:p></o:p>
      He "calculates an 18-fold decrease in influenza deaths between the 1940s and 1990s, a trend that began far before the introduction of widespread vaccination." With a narrow focus on the United States, a first world country, it is not surprising that he concludes that "improvements in living conditions, nutrition and other public health measures, influenza death rates substantially declined across the 20th century."
      <o:p></o:p>
      In the news release Doshi is reported to claim that commercial interests may be fanning the flames of pandemic fear. He concludes "the next influenza pandemic may be far from a catastrophic event."
      <o:p></o:p>
      This is a rather myopic view of the potential impacts, both direct and indirect, of a deadly pandemic. Assuming that the most likely current candidate for a novel pandemic virus is H5N1, with a current overall CFR of 63&#37;, I think he needs to reconsider his data.
      <o:p></o:p>
      He also needs to reconsider his tacit assumptions about the stability of the health care system in the <st1:place w:st="on"><st1:country-region w:st="on">United States</st1:country-region></st1:place>. Many anecdotal posts here at FluTrackers indicate that with a 30% CAR the <st1:country-region w:st="on"><st1:place w:st="on">U.S.</st1:place></st1:country-region> health care system will be brought to its knees. Any first world health care advantages developed during the 20th century i.e. "intensive care units, respirators, antiviral agents and antibiotics" will evaporate very quickly, and primary as well as secondary deaths attributable to a pandemic will numerically explode.
      <o:p></o:p>
      This article allows Doshi to add a publication to his graduate student vita, but the article, with a naive view of a pandemic, does little to further our understanding of the nature of world-wide influenza pandemics. It is unfortunate that the peer reviewers at the American Journal of Public Health didn't scrutinize this article in more detail.<o:p></o:p>
      http://novel-infectious-diseases.blogspot.com/

      Comment


      • #4
        Re: Study challenges notion of 'pandemic' flu

        a pandemic typically infects 20-40% of the population,
        while seasonal flu only infects 5-20% and that is
        for 3 different serotypes and also different types
        within the same serotype whose common anchestor is
        more than 1 season ago in some segment.
        I'm interested in expert panflu damage estimates
        my current links: http://bit.ly/hFI7H ILI-charts: http://bit.ly/CcRgT

        Comment


        • #5
          Re: Study challenges notion of 'pandemic' flu

          Excellent response, Laidback Al.

          I hope it was submitted to the journal as a publishable commentary.

          J.

          Comment


          • #6
            Re: Study challenges notion of 'pandemic' flu

            Originally posted by cartski View Post
            Excellent response, Laidback Al.

            I hope it was submitted to the journal as a publishable commentary.

            J.
            I agree with Cartski.

            btw - We are a publishable commentary. lol

            Comment


            • #7
              Re: Study challenges notion of 'pandemic' flu

              Originally posted by gsgs View Post
              a pandemic typically infects 20-40% of the population,
              while seasonal flu only infects 5-20% and that is
              for 3 different serotypes and also different types
              within the same serotype whose common anchestor is
              more than 1 season ago in some segment.
              Please. Any links for the above "definition"?

              Comment


              • #8
                Re: Study challenges notion of 'pandemic' flu

                Originally posted by Florida1 View Post
                I agree with Cartski.

                btw - We are a publishable commentary. lol
                Yes, I agree.

                What I meant was putting the commentary in the journal's letters or replies box so that a thorough reader of the journal article will immediately see the contrary view, with reference to FT and other research publication services.

                J.

                Comment


                • #9
                  Re: Study challenges notion of 'pandemic' flu

                  Originally posted by gsgs View Post
                  a pandemic typically infects 20-40% of the population,
                  while seasonal flu only infects 5-20% and that is
                  for 3 different serotypes and also different types
                  within the same serotype whose common anchestor is
                  more than 1 season ago in some segment.
                  As I understand available literature on the subject, the clinical infection rate for the 1918 Pandemic in the US was 29%, for the 1957 Pandemic it was 24%, and for the 1968 Pandemic 15%. In talking with US business people about 1968 and the absentee rates experienced, 1968 was just another flu season. Not much to talk about.

                  Comment


                  • #10
                    Re: Study challenges notion of 'pandemic' flu

                    Originally posted by cartski View Post
                    Excellent response, Laidback Al.

                    I hope it was submitted to the journal as a publishable commentary.

                    J.
                    Thanks for the comment. No, it was not submitted to the journal.

                    <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p>I was unable to access the full article so I must give Peter Doshi the benefit of the doubt. </o:p>Most of my comments responded to the press release (post 1). Without access to the full article it is hard to know what his position specifically is.
                    <o:p></o:p>
                    I hope that the news office at an august institution such as MIT has not sunk to the depths of manipulating author?s quote to creating sensationalistic, tabloid-like headlines for an official press release.
                    http://novel-infectious-diseases.blogspot.com/

                    Comment


                    • #11
                      1968-70 Pandemic seasons were no walk in the park.

                      Trends for Influenza-related Deaths during Pandemic and Epidemic Seasons, Italy, 1969–2001. http://www.cdc.gov/EID/content/13/5/694.htm

                      Italy's second year was 3-fold greater than the outbreak in the US, and twice as high as the rest of Europe. I don't think anybody would typify the 1969-70 season as mild in Italy, Europe, or parts of Asia/South Pacific.

                      Multinational Impact of the 1968 Hong Kong Influenza Pandemic: Evidence for a Smoldering Pandemic. http://www.journals.uchicago.edu/doi/abs/10.1086/431150

                      See Fig. 2, P&I mortality trends for Seasons 1 and 2 for H3N2, 6 countries.

                      H3N2 is a butt-kicking human influenza strain, with much higher case rate, harsher symptoms and more complications/deaths than other strains.

                      Comment


                      • #12
                        Re: Study challenges notion of 'pandemic' flu

                        On re-reading the news article and abstract of this study, I noted the reference to CDC. The article goes to the credibility of the scientists at CDC, in effect saying that they errred in determining when a pandemic actually occurs.

                        I wonder if CDC plans an official response.

                        J.

                        Comment


                        • #13
                          Going off on a tangent - again.

                          Firstly let me add my thanks to Al for his typically Al like intervention.

                          If we agree that a flu pandemic is an epidemic with extended global scope the reason is normally because it is new, in the sense its hosts immune systems’ are not primed to react to it, and so it spreads more easily as it does not just spread until it hits a population that had it last year so dropping Ro < 1. The virulence of the strain in question is largely unrelated - as long as it does not kill its host before they have a chance to infect someone else.
                          But that is not really what I want to say. I would like to bring up a rather obvious point which I am not sure has been aired enough. It is to do with our current top pandemic candidate HPAI H5N1 and it’s the fact that it is HP. While we know the serotypes for the last century’s pandemics we can not go much further back and they have all been LP. This is not an academic distinction while HP stands for Highly Pathogenic - and that refers to its effect on poultry not us - it is more technically a description of the number - and type - of bases at the Hemagglutinin cleavage site. While this may seem a rather odd way to split Type A influenza into two groups what it is actually measuring is very important. For the virus to infect a cell it needs to bind to the cell surface and then be cleaved to get into the cell. The cleaving is done by a protease enzyme supplied, not by the virus, but by the host. Both seasonal type A flus and all know past pandemic flus have had short cleavage sites which can only be cleaved by a limited range of proteases, normally tryptase clara which is localised to clara cells in the respiratory tract. HP H5N1’s polybasic cleavage site can be snipped by many proteases which can be found all over the body. Once H5N1 (or any HP flu) infects you it has the ability to get in to a wide range of cell type and manifests it self not just as a respiratory tract infection. Although 1918 H1N1 was significantly more virulent that ’57, ’68 or our seasonal flus it was ‘only’ an LP flu. My point is H5N1 is very different not because our immune systems have not met it before but because – to the best of my knowledge – it is the first time man has met a not exclusively respiratory form of flu.

                          To continue this train of thought to its logical conclusion should we be buying face masks? Just because all the forms of flu we have met before were via coughs and sneezes it does not hold true for HP H5N1. The natural reservoir for Type A flus is in birds and for them infection is via the intestinal tract, mammals are a bit of a side show in the flu story. We think of flu as being caught via the nasopharynx but that is because that is where the clara cells are, if H5N1 does not need them we may need to start thinking of it more in terms of intestinal transmission. Even in birds it is requiring some difference in sampling. Typically other strains are collected by cloacal swab but experience is showing for H5N1 better results are gained from nasal swabs. I am sure there is an expression in colloquial English that covers this something about having got things *** about face.

                          Wash your hands!

                          JJ<o:p></o:p>
                          Last edited by JJackson; May 3, 2009, 07:05 AM. Reason: reformat to verbena typeset

                          Comment


                          • #14
                            Re: Study challenges notion of 'pandemic' flu

                            So, if I understand JJackson's excellent analysis, there's yet another huge gaping hole in Doshi's work; namely, he has assumed that all human pandemic flus have the same pathogenic potential. In other words, he's assumed that all human flu variants have the same power to produce disease.

                            His "challenge [of the] common beliefs about the severity of pandemic influenza" is no challenge at all because he fails to consider the biological differences between LP and HP viruses.

                            Has anyone read the full article? Is the assumption Doshi makes there also?

                            J.

                            Comment


                            • #15
                              Re: Study challenges notion of 'pandemic' flu

                              hard to imagine that something can go pandemic quickly
                              as seasonal flu without respiratory transmission
                              I'm interested in expert panflu damage estimates
                              my current links: http://bit.ly/hFI7H ILI-charts: http://bit.ly/CcRgT

                              Comment

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