wpro designated a rumor surveillance officer to develop and implement the rumor surveillance system for avian influenza in animals and humans . this officer actively assessed media sources and email - based public health discussion and regularly contacted the who network to identify rumors . most were english - based media sources ; however , some were also in japanese and arabic . to increase the scope of the active media search , this officer also accessed the global public health intelligence network ( 10 ) , an electronic surveillance system that continuously monitors > 600 media sources and biomedical journals in a number of languages , including chinese , spanish , english , and french . each rumor was followed up by an email or a telephone request to the relevant who country office to investigate its veracity . overall , the onus of the verification process was in the hands of the affected countries health authorities . the authorities had to demonstrate to who that appropriate investigations were conducted to deem rumors correct or incorrect . to ensure this process , who sometimes supported rumor verification by assisting in laboratory testing or shipment of isolates . once available , the outcome of the investigation was disseminated to who stakeholders , including the outbreak response team . for events reported in the media , wpro s media officers made information publicly available through press releases and media interviews , as well as providing up - to - date information on the who web site ( http://www.who.int ) . from january 20 to february 26 , 2004 , a total of 40 rumors were identified , most within 4 weeks of the outbreak alert ( figure ) . the rumors concerned 12 countries and 1 special administrative region . of the total rumors received , 19 ( 48% ) were received from the media , 18 ( 45% ) from the who network , 2 ( 5% ) from embassy staff living in affected countries , and 1 ( 2% ) from promed digest with a media source as the origin . nine ( 23% ) rumors were confirmed to be true events : 5 in china and 1 each in cambodia , japan , laos , and south korea . of the incorrect rumors , 6 were in china , 6 in laos , 4 in vietnam , 4 and in hong kong , 3 in cambodia , 2 in germany , and 1 each in bangladesh , indonesia , japan , malaysia , saudi arabia , and singapore . number of rumors received from january 20 to february 26 by source of rumor , western pacific regional office ( wpro ) of the world health organization ( who ) , 2004 . the average period for verification of true events was 2.7 days ( range 15 days ) . the average period to verify that a rumor was incorrect was 9.3 days ( range 126 days ) . sixty percent of the rumors related to human outbreaks , of which 1 was true , and 40% to animal outbreaks , of which 8 were true . the table provides examples of rumors received during the 40-day study , the outcomes of the investigation , and the public health action taken . the remaining 32 rumors are not shown for reasons of brevity and privacy ; however , not all rumors resulted in public health action after the verification process . this finding was expected because the high sensitivity of the system decreased the predictive value positive . a similar pattern was also observed during the 2003 sars outbreak , when most rumors were received within the first 7 weeks of the public health alert ( 11 ) . the decreased rate of rumor detection later in the outbreak is consistent with allport and postman s basic law of rumor ( 12 ) . according to this law , the amount of rumors in circulation is roughly equal to the importance of the rumor multiplied by the uncertainty surrounding the rumor . we found that , as more information became available about the outbreaks and about the h5n1 virus , fewer rumors circulated . this decrease was despite the fact that the importance of the disease remained high because of the ongoing risk for evolution of a pandemic influenza strain . through rumor surveillance , who assisted affected countries by issuing guidelines , providing technical expertise , and mobilizing supplies . an important part of rumor surveillance is the timely dissemination of accurate information to reduce misunderstanding and unwarranted concern , especially for rumors reported in the media . one example was the need to address the international concern that arose about the rumor that pigs were infected with avian influenza ( 13 ) . if the rumor had not been reported to be incorrect publicly after the verification process , health authorities may have heightened avian influenza surveillance to include the investigation of persons with symptoms of influenza and a history of contact with pigs . the literature lacks guidance on how to establish and operate enhanced rumor surveillance during large outbreaks . based on our experience and drawing on the recommendations in standard texts on public health surveillance ( 14,15 ) , we suggest the following criteria for developing rumor surveillance : 1 ) define the goals of surveillance as part of an early warning system in which each rumor deserves investigation to determine its veracity ; 2 ) apply a case definition that will have a high level of sensitivity ( and therefore a relatively lower specificity ) to identify the event of interest early in the outbreak ; 3 ) articulate clearly the steps to be undertaken to assess the veracity of the rumor , the criteria for deeming the verification process complete , and the ethics and confidentiality in conducting investigations ; 4 ) clarify the actions to be taken if the rumored events are true , or incorrect , or if the response of the verifying authority lacks credibility ; 5 ) delegate responsibility for data collection , management of the rumor database , and verification to a person trained in surveillance . this person must have access to relevant national and international networks and appropriate negotiation skills to investigate the veracity of the rumors . in selected instances , multilingual staff may be essential ; 6 ) include among the data sources print and electronic media , the global public health intelligence network , national health authorities , and professional bodies and networks . consider mechanisms for the public to report rumors through a hotline or an email address ; 7 ) develop mechanisms to provide regular updates on current verification activities , the number of rumors investigated , and their outcomes to the outbreak response team ; 8) provide regular feedback on the outcomes of investigations to those who provided data , and where appropriate , to the international community ; and 9 ) evaluate the efficiency and effectiveness of the investigations and upgrade the rumor surveillance system through a process of continuous quality improvement .
we describe the enhanced rumor surveillance during the avian influenza h5n1 outbreak in 2004 . 
 the world health organization s western pacific regional office identified 40 rumors ; 9 were verified to be true . 
 rumor surveillance informed immediate public health action and prevented unnecessary and costly responses .