In his Essay 'Pandemics: avoiding the mistakes of 1918' (Nature 459, 324–325; 2009), John M. Barry writes that during an influenza pandemic “telling the public the truth is ... paramount”. Truth telling is, he notes, the basis for trust and compliance in public-health measures. However, the H1N1 influenza debate in the Netherlands illustrates that things may not be that simple.

In the current 'swine flu' pandemic, the expert sources of information and guidance for the Dutch public are Albert Osterhaus of the National Influenza Centre in Rotterdam and Roel Coutinho at the National Institute for Public Health and the Environment in Bilthoven. These two experts are not strangers to such challenges: both have often been consulted on risks to the public since the 1980s.

Since the early years of the pandemic debate, Osterhaus has kept us informed about the greater picture, warning us of an 'imminent' flu pandemic (see, for example, J. C. de Jong et al. Nature 389, 554; 1997, and the Dutch newspaper De Volkskrant, 2 May 2009). Coutinho, by contrast, has stuck to the immediate facts (see, for example, the newspaper NRC Handelsblad, 14 March 2006), and cautioned us that “there's no need to panic” (see, for example, the newspaper Het Parool, 1 May 2009). In communicating their different perspectives, these virologists were conveying conflicting messages to the general public, even though their aims were the same — to protect the public's health.

Public understanding, therefore, cannot hinge only on experts telling the truth as they see it: also important is how the public interprets mixed messages. It is the public's ability to assess the relative value of expert information that helps to stimulate the trust and compliance needed to follow recommended public-health measures.

That trust will be particularly crucial during the months to come, in implementing the planned vaccination of the entire Dutch population — and the related information campaign — following the announcement made by the World Health Organization on 11 June of a pandemic, which is expected to strike the Netherlands with force this autumn.