In recent years, avian influenza, so-called “bird flu,” has become a major concern. Aquatic bird species world-wide serve as the natural host for all of the subtypes of type A influenza known. Usually these viruses cause little or no illness in their natural host. Occasionally, however, certain subtypes mutate and become capable of causing severe illness with very high mortality, particularly within domestic poultry populations. These novel subtypes can also become capable of infecting humans, resulting in very severe disease with high mortality. Should sustained human-to human transmission of a novel subtype of influenza occur, the result would likely be a worldwide epidemic, or influenza pandemic.
Avian Influenza
Influenza A (H5N1) virus – also called “H5N1 virus” – is an influenza A virus subtype that occurs mainly in birds, where it is highly contagious and often deadly. H5N1 virus does not usually infect people, but infections with these viruses have occurred in humans. The current highly pathogenic avian influenza A (HPAI H5N1) epizootic (animal outbreak) in Asia, Europe, the Near East, and Africa has resulted in over 300 human infections and 200 deaths. It is likely that H5N1 virus infections among domestic poultry have become endemic in certain areas and that sporadic human infections resulting from direct contact with infected poultry and/or wild birds will continue to occur. So far, the spread of H5N1 virus from person-to-person has been very rare, limited and unsustained. However, this epizootic continues to pose an important public health threat.
While a major focus of national pandemic planning efforts has been on the potential for H5N1 to become capable of sustained human to human transmission, it is important to note that other avian influenza viruses have been implicated in human disease (including HPAI H7N7, and LPAI H9N2, H7N2, H7N3). It is essential that current influenza surveillance programs provide for rapid detection of any novel strain.
Most experts feel that another pandemic is inevitable and many feel that we are now overdue. With today’s global interconnectivity, even a mild to moderate pandemic would rapidly affect the world with rates of infection of up to 50%, mortality measured in the millions (100,000s in the U.S.) and severe social, infrastructure and economic disruptions.
Pandemic Influenza and Public Health Laboratories
In a pandemic, laboratory testing will help guide the implementation of public health measures such as distribution of vaccine and anti-virals, and community mitigation strategies such as decisions to close schools. The capability of differentiating seasonal influenza from pandemic influenza depends upon the rapid confirmation and characterization that is available through the public health laboratories. State laboratories are collaborating with health partners to develop pandemic response plans and conduct emergency response exercises.
CDC has provided PCR protocols to public health laboratories to detect H5N1 viruses. These tests are used when a patient is considered to be at risk for avian influenza due to travel history and exposure to birds in areas where H5N1 has been found. Public health laboratories remain poised to increase testing capacity on short notice in the event of a pandemic.
APHL and Pandemic Influenza
APHL has been working collaboratively with CDC and member laboratories to strengthen laboratory capability to detect novel strains of influenza and to provide the surge testing capacity that may be needed in a pandemic. Examples of the APHL activities include:
• Evaluation of new tests developed by CDC to detect and subtype influenza viruses.
• Training for all state public health laboratories in rapid PCR methods to detect and subtype influenza viruses
• Support for state outreach to clinical laboratories to improve knowledge of influenza testing practices and to develop pandemic response plans
• Outreach to the clinical laboratory community at the national level to assure coordinated pandemic planning, application of appropriate testing strategies throughout a pandemic, and adequate surge testing capacity.
• Collaboration with state public health laboratories and CDC to allow for the release of genetic blueprints for influenza viruses (link to press release) into a database accessible to researchers worldwide, allowing for greater access to data on a variety of influenza virus samples obtained from patients in the United States, including avian influenza H5N1 if it should arrive here.