Bulletin of the World Health Organization 2011; 89:
Charles Penn (editorial) Future perfect? Improving preparedness through the experiences of the influenza A (H1N1) 2009 pandemic (p470)
Roundtable debating the issues
Peter Doshi  The elusive definition of pandemic influenza pp532-538
Daniel J Barnett  Pandemic influenza and its definitional implications (p539),
Luc Bonneux &Wim Van Damme Health is more than influenza (pp539–540),
Heath Kelly The classical definition of a pandemic is not elusive (pp540–541),
Nick Phin Living forwards, understanding backwards  (pp541–542) and
Angus Nicoll  Planning for uncertainty: a European approach to informing responses to the severity of influenza epidemics and pandemics  (pp542–544)

This collection of article is intended to clarify the issues that arose, during the 2009 pandemic around definitions of the pandemic term, both in a theoretical and practical way. This Public Health Development from ECDC describes some of the background and complex events in approximately chronological order.  In 2009, governments throughout the world mounted responses to the 2009 A(H1N1) pandemic. These efforts were on the premise that pandemic and seasonal influenza potentially required different management and responses.(1)  The Director General of the World Health Organization (WHO), followed the actions dictated by the International Health Regulations and acted on the advice of a global emergency committee selected from experts nominated by member states,  declared the confirmed outbreak of novel A(H1N1)2009 influenza to be a ‘pandemic’ in June 2009.(1) As indeed it was according to the long standing definition in the Dictionary of Epidemiology “an epidemic occurring worldwide, or over a very wide area, crossing international boundaries and usually affecting a large number of people” (2).

Later some persons, mostly new to influenza issues, suggested that the declaration of a ‘pandemic’ was only because WHO had changed its own definition of a pandemic and that this was bowing to commercial pressures.(1) Concern was increased by WHO’s decision to withhold publication of the names of its H1N1 advisory Emergency Committee until the pandemic was declared over in August 2010. In response, WHO denied having changed any definitions and defended the scientific validity of its decisions, citing ‘numerous safeguards’ for handling potential conflicts of interest. Doshi suggests in his article that both parties are partially correct, and to resolve it he proposes a re-evaluation of the way in which emerging threats should be defined, taking into account that the simple act of labelling a disease can have enormous social, economic and political implications. Doshi’s article indicates how easy it was for people to confuse description with definition of a pandemic. WHO’s Pandemic Preparedness homepage had contained statements about how an influenza pandemic could resulting in enormous numbers of deaths and illness and that less informed readers had then assumed that therefore all pandemics would result in such mortality. This process of perhaps over-stating the risk has been described as risk advocacy by Thomas Abraham.(3) Dr Fineberg, independent chairman of the WHO-appointed International Health Regulations (IHR) Review Committee which evaluated WHO’s response to the 2009 influenza A(H1N1) pandemic – identified the ‘definition of pandemic influenza’ as a critical element in his committee’s review.(1)

In the final report of the review released on the 5^th May 2011, the Fineberg committee faulted WHO for ‘inadequately dispelling confusion about the definition of a pandemic’ and noted WHO’s ‘reluctance to acknowledge its part in allowing misunderstanding’. Doshi also notes that none of the influenza preparedness guidelines - first developed in 1999 and revised in 2005 and 2009 - contain what could be considered a formal WHO definition of a pandemic and that WHO’s six-point pandemic phase determinations did not correlate with clinical severity but rather the international spread and the risk of disease occurrence. The Fineberg report recommends that WHO ‘develop and apply measures that can be used to assess the severity of every influenza epidemic’, while noting that ‘assessing severity does not require altering the definition of a pandemic to depend on anything other than the degree of spread’ (1). Finally the article by ECDC indicates a way this is being done in Europe.(4)

1) WHO Report of the Review Committee on the Functioning of the International Health Regulations (2005) and on Pandemic Influenza A (H1N1) 2009 (Fineberg Report) Final submitted to the World Health Assembly 2011 http://apps.who.int/gb/ebwha/pdf_files/WHA64/A64_10-en.pdf

2) Last J. A dictionary of epidemiology (4^th Edition) Oxford University Press 2001.

3) Abraham T, The Price of Poor Pandemic Communication. BMJ 2010 http://www.bmj.com/cgi/section_pdf/340/jun09_2/c2952.pdf

4) Nicoll A.  Planning for uncertainty: a European approach to informing responses to the severity of influenza epidemics and pandemics  Bull WHO 2011; 89: 542–544.