Global Monitoring

Influenza is a Threat to Global Health

The influenza virus has an ability to significantly mutate or change over time to a form that can cause a worldwide pandemic with increased severity of illness and deaths. For example, the influenza pandemic of 1918 killed more than 20 million people, and perhaps as many as 50 million people, around the world.

In 1997, an outbreak of a new, deadly strain of influenza A (H5N1) occurred in poultry in Hong Kong. Since that time, the virus has mutated and has passed from sick poultry to over 300 humans worldwide of which nearly 60% have died. So far, human-to-human transmission has been very limited and not sustained.

The H5N1 virus continues to change and poses a significant potential threat as the cause of the next pandemic.

Sharing of Influenza Virus Samples is Critical to Global Health Security

Global health benefits from a robust, global network for surveillance and the sharing of seasonal, avian and other potential pandemic viruses, and genetic sequence information from them. Viral specimens are required to assess the pandemic potential of the virus, and to ensure the rapid development of new, more effective diagnostics, medicines and vaccines. The data derived are also vital for early containment responses, and for identifying triggers for non-pharmaceutical interventions and other responses that could reduce the illness and death caused by influenza infections.

Each time the H5N1 virus causes an outbreak in birds or infects a human, it is critical that sophisticated laboratories with the necessary state-of-the-art technology analyze specific virus strains to characterize changes in the virus, and determine if the arsenal of diagnostic tests and medicines against influenza is still effective against the new virus. Current pre-pandemic vaccines can not be guaranteed to protect the population from H5N1 infection if it mutates to become easily spread from human to human. In addition, scientists must continue to monitor the strains causing seasonal influenza for significant genetic changes that might increase illness or deaths.

For more than 50 years, the World Health Organization (WHO) has coordinated the Global Influenza Surveillance Network (GISN), a worldwide monitoring system that has enabled the international public health community to share and analyze influenza viruses, to further the understanding of their evolution, epidemiology, and impact. The GISN is currently comprised of four WHO Global Collaborating Centers (CC) that work primarily on human influenza, one of which is located in the United States at the Centers for Disease Control and Prevention (CDC) within the U.S. Department of Health and Human Services (HHS) and a fifth WHO CC located at St. Jude Children’s Research hospital that works primarily on influenza in animals. The network also includes 121 institutions the WHO Secretariat recognizes as WHO National Influenza Centers (NICs), in 93 countries. These NICs typically collect specimens in their country and perform primary virus isolation and preliminary antigenic characterization. If a new virus with pandemic potential infects humans, the GISN National Influenza Centers might not have the necessary tools and laboratory-containment capability to identify and characterize the newly emerging influenza viruses. In such instances, Collaborating Centers and other key reference laboratories (such as the WHO H5 reference Laboratories) often receive original, clinical specimens from infected patients for diagnosis, virus isolation, virus characterization, risk assessment, and the development of candidate vaccines. WHO reference laboratories isolate influenza viruses from the patients’ clinical specimens and characterize them. Genetic sequence information from viruses collected over time and, from different geographical areas, can help track evolutionary changes in the virus and identify mutations that could be important markers for severe disease in humans and their ability to transmit among humans. Epidemiological findings, along with properties of the virus, remain critical to understand the implications of viral changes, such as the efficiency of human-to-human transmission and severity of disease.

The GISN Openly and Freely Shares Virus Samples and Information

The GISN receives numerous requests to share samples of viruses contributed by many countries around the world, and the information derived from them. GISN member laboratories send these virus isolates are sent to any entity that requests them, as long as the recipient institution can handle the dangerous pathogen appropriately and follows their national regulations. Bio-containment Safety Level 3 (BSL-3) enhanced conditions are necessary to protect laboratory workers and the environment when scientists work with highly pathogenic avian influenza viruses, including highly pathogenic H5N1 viruses, and often require permission from national government authorities to meet export and import requirements.

For example:

Upon request, WHO Collaborating Centers and H5 reference laboratories have sent isolated viruses and/or vaccine-candidate viruses to a number of countries, including the people’s Republic of China, India, Indonesia and Viet Nam;

GISN laboratories, including Collaborating Centers, have traditionally provided historical and contemporary influenza viruses on request to academic researchers and to companies that wish to develop new diagnostic tests or novel vaccines. Access to reference viruses (a variety of subtypes, vaccine strains and other influenza viruses) has made it possible to develop rapid diagnostic test kits, antiviral drugs, and new vaccines that benefit global health generally;

More than 1545 gene sequences have been published from H5N1 viruses isolated from Humans in countries such as Hong Kong, Thailand, Viet Nam, Egypt and Indonesia. The WHO Collaborating Center for the Surveillance, Epidemiology and Control of Influenza at HHS/CDC has analyzed virus samples and publicly posted H5N1 gene sequences to the Influenza Sequence Database, maintained at Los Alamos National Laboratory (LANL), and at the GenBank website, a public-access library for virus sequences managed by the HHS National Institutes of Health. These information repositories contain genetic sequences only and do not receive viral samples. The Influenza Sequence Database, housed and maintained by LANL, is one of several viral databases that had been established over the years for the public health and research communities, including databases for HIV, Hepatitis C and Human Papillomavirus sequences.

Rapid Response to a Pandemic Requires Rapid Sharing of Viruses

Influenza vaccines are the cornerstone for the prevention and control of influenza and its severe complications. However, influenza viruses evolve rapidly so vaccines used to prevent infection are no longer optimally effective when a variant virus emerges. Producing influenza vaccines that are well-matched to circulating viruses that cause disease is a challenge for virologists and vaccine manufacturers, and can take several months. There is often a very short time between the recognition of significant influenza virus variants (that become vaccine candidates for seasonal influenza and potential pandemic vaccines) and the need to incorporate those candidate-vaccine viruses into vaccines produced by manufacturers. For this reason, GISN, NICs, and WHO Collaborating Centers share with each other recently isolated influenza viruses, including those with pandemic potential, without restrictions, for further analysis or use as a vaccine strain. The GISN makes a concerted effort to send the recommended vaccine strains and high-growth reassortants (see glossary of terms (PDF - 149KB)) simultaneously and free-of-charge to all entities worldwide that are seeking to produce influenza vaccines, to maximize the amount of vaccine that is produced, tested to meet national regulatory requirements, and distributed for use prior to the next influenza season or pandemic.

Preparedness for Seasonal and Pandemic Influenza Requires a Global Partnership

The early detection of changes in influenza viruses and the rapid development of effective vaccines are the keys to defending against influenza each year and to responding to the possibility of a pandemic. The cycle of surveillance and vaccine formulation is a continuing process that requires the combined resources of the WHO Secretariat, the United States and other Governments, State/Provincial health authorities, the medical community, and vaccine and drug companies. The identification, manufacture, and distribution of new influenza vaccines for novel viruses with pandemic potential takes at least six months, given current technology. The open and timely sharing of virus samples and sequence data is vital as countries work together to limit the spread of novel influenza viruses. The GISN’s activities demonstrate that the combined efforts of countries under the coordination of the WHO form a reliable, common defense against influenza. For that to remain effective, however, the commitment by all countries to share viruses and data freely and at the earliest possible opportunity is essential.