International flu surveillance

The successful surveillance of influenza involves both national and international collaboration between a variety of organisations.

The World Health Organization Influenza Surveillance Programme

In 1947, World Health Organization (WHO) established a global network for influenza surveillance, largely in response to concerns regarding the threat posed by pandemic influenza. The function of this network is to detect the emergence and spread of influenza viruses that differ antigenically from previously circulating strains, that may signal a need to update the composition of the influenza vaccine. The network has expanded considerably since its inception and includes four international WHO collaborating centres located in London, Atlanta, Tokyo, and Melbourne, and over 100 designated WHO national influenza reference centres (NIRC) in more than 80 countries. Please see: WHO for international information.

National Surveillance

In the UK the surveillance of influenza is co-ordinated and collated by the Influenza/Respiratory Virus Section of the Health Protection Agency (HPA) at Colindale. HPA Colindale receives timely reports from separate schemes run in England, Wales, and Scotland, which use networks of general practioners to record clinical consultations. Additional information is obtained from the monitoring of weekly respiratory activity from a sentinal boarding school scheme and also emergency bed uptake in the NHS. All virological data both from the Respiratory Virus Unit, Virus Reference Department reference laboratories at Colindale and from a countrywide laboratory reporting system as well as community based sampling schemes using general practioners, are also collated by the Influenza/Respiratory Virus Section and combined with the clinical information for timely surveillance and reporting purposes. For further details about the UK see sources of data for influenza surveillance in the United Kingdom.

National Influenza Reference Centres

The Respiratory Virus Unit (RVU) of the Virus Reference Department (VRD) at HPA Colindale is the WHO National Influenza Reference Centre for the United Kingdom. One of the functions of the RVU is to act as a referral centre for influenza viruses isolated in public health laboratories and NHS laboratories in the United Kingdom. The antigenic and genetic properties of the viruses are analysed and compared to previously circulating influenza viruses. A representative selection of the viruses is sent from the UK to the international centre at Mill Hill for comparative analysis.

International Collaborating Centres

The primary function of the four international centres is the detailed identification and comparison of influenza viruses sent from different countries. The centres provide assistance, reagents and reference material to the NIRC. The collaborating centres also assess, by serology on vaccinated individuals, whether current vaccines would be expected to protect against recently isolated virus strains. In the UK this role is performed in collaboration with the National Institute for Biological Standards and Control (NIBSC). In February each year the most recent information from the international collaborating centres is reviewed by the WHO in Geneva, in order to make a recommendation to vaccine manufacturers on the selection of influenza strains for the vaccine to be used in the northern hemisphere for the coming season. A similar meeting is held annually in September for the southern hemisphere.

Circulation of Information

The WHO global network is based on international collaboration in which influenza surveillance data is shared worldwide. The information received by the WHO in Geneva from international and national collaborating centres is released in the Weekly Epidemiological Record, as are the annual recommendations for the influenza vaccine composition. Each country organises the distribution of data locally: for example, in the UK a weekly activity report is circulated by the Respiratory Diseases Department at HPA Colindale. In Europe, several other systems circulate information, often weekly, in addition to the WHO programme. The European Influenza Surveillance Network (EISN) includes all 27 EU countries, Iceland and Norway and is co-ordinated by the European Centre for Disease Prevention and Control (ECDC). Virological and epidemiological data is collated from these countries through the European Surveilance System (TESSy) and issued by ECDC as a weekly public report. Other schemes such as the European Working Group on Influenza (ESWI) also distribute information on influenza surveillance between participating countries.

Last reviewed: 16 February 2012