Massachusetts Institute of Technology, Cambridge, MA, USA 02139
To the Editor:
Since the H1N1 outbreak, the World Health Organization (WHO) appears to be distancing itself from the idea that it ever promoted the concept of an influenza pandemic as an inevitably disastrous event. Last May, the WHO Director-General declared that highly pathogenic avian influenza “H5N1 has conditioned the public to equate an influenza pandemic with very severe disease and high mortality. Such a disease pattern is by no means inevitable during a pandemic. On the contrary, it is exceptional.” 
I disagree. It is public health organizations–not viruses–that have shaped the public’s understanding of pandemic influenza.
In the BMJ last September, I documented how the WHO altered its longstanding definition of “influenza pandemic” a few weeks after the emergence of H1N1 . The Organization deleted the phrase “enormous numbers of deaths and illness” from the definition. By the new definition, pandemics need not be severe.
The classification of the H1N1 outbreak as a “pandemic” has been a central concern at the ongoing Council of Europe investigation into the World Health Organization’s (WHO) handling of H1N1. UK Member of Parliament Paul Flynn (rapporteur of the inquiry) stated that “A pandemic cannot be whatever the WHO declares it is.” 
In a “Key Messages” document prepared in response to the inquiry, the WHO writes:
“WHO did not change the definition of pandemic in the course of this outbreak. … Some of the confusion may stem from the fact that there was a document on WHO’s website for some months that said a pandemic would include “enormous amounts of cases and deaths”. This was removed when it was brought to our attention. This information was never part of the formal definition of a pandemic and was never part of documents sent to Member States for their preparedness work. We regret the confusion it has caused.” 
However, what the WHO calls “a document” was in fact the WHO’s “Pandemic preparedness” homepage , and the definition including “enormous numbers of deaths and illness” remained on the WHO website not “for some months” but at least six years . Indeed, numerous WHO policy documents over past years consistently described catastrophic morbidity and mortality as a fundamental characteristic of all influenza pandemics. (See box)
Now a second widely cited WHO webpage has been altered. The document was formerly titled “Ten things you need to know about pandemic influenza” , four of which included: “Widespread illness will occur”, “Medical supplies will be inadequate”, “Large numbers of deaths will occur”, and “Economic and social disruption will be great”. The document has been renamed: “Ten concerns if avian influenza becomes a pandemic” . (Table)
By altering the title, the WHO has changed self-described must-know information about “pandemic influenza” into “concerns” about “avian influenza”. Most troubling, however, is that the contents (and datestamp) of the document remain unchanged. This raises serious ethical questions about transparency that must be addressed by all committees investigating the pandemic .
April 12, 2010
Acknowledgements: Tom Jefferson, for his help locating relevant policy documents.
Box. WHO descriptions of pandemic influenza in policy documents
WHO 1999: “At unpredictable intervals, however, novel influenza viruses emerge with a key surface antigen (the haemagglutinin) of a totally different sub-type from strains circulating the year before. This phenomenon is called “antigenic shift”. If such viruses have the potential to spread readily from person-to-person, then more widespread and severe epidemics may occur, usually to a similar extent in every country within a few months to a year, resulting in a pandemic. Annex B provides more information on these issues, and Annex C discusses hypotheses about the origin of pandemic viruses.” 
WHO 2004: “An influenza pandemic occurs with the appearance of a new influenza virus against which none of the population has any immunity. This results in several simultaneous epidemics worldwide with enormous numbers of cases and deaths.” 
WHO 2005: ‘Influenza pandemics (worldwide epidemics) have occurred at irregular and unpredictable intervals, and have been associated with substantial morbidity, mortality and economic cost. The influenza A virus can cause pandemics and these occur as a result of changes in the virus leading to a sub-type to which no one has immunity, that can spread easily among humans and can give rise to serious disease. Appearance of such a subtype may lead to several simultaneous epidemics worldwide resulting in high numbers of cases and deaths and placing an immense burden on healthcare systems.” 
WHO 2005: “An influenza pandemic (or global epidemic) occurs when a new influenza virus subtype appears, against which no one is immune. This may result in several simultaneous epidemics worldwide with high numbers of cases and deaths.” 
WHO 2008: “An influenza pandemic occurs when a novel influenza virus appears against which the human population has limited or no immunity, and which transmits efficiently from person to person, resulting in several simultaneous epidemics worldwide with the potential for considerable morbidity and mortality.” 
Table. Changing WHO webpages
|Before 2009 H1N1 outbreak||Since 2009 H1N1 outbreak||Date of change|
|WHO 2003: “An influenza pandemic occurs when a new influenza virus appears against which the human population has no immunity, resulting in epidemics worldwide with enormous numbers of deaths and illness” ||WHO: “An influenza pandemic may occur when a new influenza virus appears against which the human population has no immunity” ||May 2009 |
|WHO 2005-2009: “Ten things you need to know about pandemic influenza” ||WHO: “Ten concerns if avian influenza becomes a pandemic” ||Between June 2009  and 17 February 2010 |
- Chan M. World is better prepared for influenza pandemic [Internet]. World Health Organization. 2009 May 8 [cited 2009 May 12];Available from: http://www.who.int/dg/speeches/2009/asean_influenza_ah1n1_20090508/en/index.html
- Doshi P. Calibrated response to emerging infections. BMJ. 2009 9;339(sep03 2):b3471-b3471. (online here)
- Watson R. WHO is accused of “crying wolf” over swine flu pandemic. BMJ. 2010 4;340(apr06 2):c1904-c1904. (online here)
- World Health Organization. WHO Key Messages – Conflict of Interest Issues [Internet]. 2010 Jan 11 [cited 2010 Apr 9];Available from: http://www.wpro.who.int/vietnam/media_centre/press_releases/h1n1_8jan2010.htm
- World Health Organization. WHO | Pandemic preparedness [Internet]. [cited 2009 May 22];Available from: http://www.who.int/csr/disease/influenza/pandemic/en/
- World Health Organization. WHO | Ten things you need to know about pandemic influenza [Internet]. [cited 2010 Apr 11];Available from: http://web.archive.org/web/20051124014913/http://www.who.int/csr/disease/influenza/pandemic10things/en/
- World Health Organization. Ten concerns if avian influenza becomes a pandemic [Internet]. 2005 Oct 14 [cited 2010 Apr 9];Available from: http://www.who.int/csr/disease/influenza/pandemic10things/en/
- World Health Organization. Influenza Pandemic Plan. The Role of WHO and Guidelines for National and Regional Planning [Internet]. 1999 [cited 2010 Apr 12]. Available from: http://www.wpro.who.int/NR/rdonlyres/A7C42115-DF0F-48CF-82AF-DDE0D734994E/0/InfluenzaPandemicPlan.pdf
- World Health Organization. Informal consultation on influenza pandemic preparedness in countries with limited resources [Internet]. 2004 Jun [cited 2010 Apr 11];Available from: http://www.who.int/csr/resources/publications/influenza/CDS_CSR_GIP_2004_1.pdf
- World Health Organization. Pandemic influenza preparedness planning Report on a joint WHO/European Commission workshop Luxembourg, 2-3 March 2005 [Internet]. Luxembourg: World Health Organization; 2005 [cited 2010 Apr 11]. Available from: http://www.euro.who.int/Document/E86578.pdf
- World Health Organization. WHO checklist for influenza pandemic preparedness planning [Internet]. 2005 [cited 2010 Apr 11];Available from: http://www.who.int/csr/resources/publications/influenza/FluCheck6web.pdf
- World Health Organization. Pandemic influenza preparedness and mitigation in refugee and displaced populations [Internet]. 2008 [cited 2010 Apr 11];Available from: http://www.who.int/diseasecontrol_emergencies/HSE_EPR_DCE_2008_3rweb.pdf
- Pandemic preparedness [Internet]. [cited 2009 Jun 9];Available from: http://web.archive.org/web/20030202145905/http://www.who.int/csr/disease/influenza/pandemic/en/
- Cohen E. When a pandemic isn’t a pandemic [Internet]. CNN.com. 2009 May 4 [cited 2009 May 5];Available from: http://edition.cnn.com/2009/HEALTH/05/04/swine.flu.pandemic/index.html
- World Health Organization. Ten things you need to know about pandemic influenza [Internet]. 2005 Oct 14 [cited 2009 Jun 9];Available from: http://www.who.int/csr/disease/influenza/pandemic10things/en/
- World Health Organization. WHO | Ten concerns if avian influenza becomes a pandemic [Internet]. [cited 2010 Apr 12];Available from: http://wayback.archive-it.org/1601/20100217155319/http://www.who.int/csr/disease/influenza/pandemic10things/en/index.html
Competing interests: I have a strong interest and have published on this topic.