Update from the CDC on avian influenza

Been a bit dry on my blog lately what with all the facts that need to be shared. I hope someone is paying attention. Cannot tell if anyone is reading this or not, but I will continue to post current news and my opinions about it.

Assessment of Current Situation

The avian influenza A (H5N1) epizootic (animal outbreak) in Asia and parts of Europe is not expected to diminish significantly in the short term. It is likely that H5N1 infection among birds has become endemic in certain areas and that human infections resulting from direct contact with infected poultry will continue to occur. So far, the spread of H5N1 virus from person-to-person has been rare and has not continued beyond one person. No evidence for genetic reassortment between human and avian influenza A virus genes has been found; however, the epizootic in Asia continues to pose an important public health threat.

There is little pre-existing natural immunity to H5N1 infection in the human population. If these H5N1 viruses gain the ability for efficient and sustained transmission among humans, an influenza pandemic could result, with potentially high rates of illness and death. In addition, genetic sequencing of influenza A (H5N1) viruses from human cases in Vietnam and Thailand shows resistance to the antiviral medications amantadine and rimantadine, two of the medications commonly used for treatment of influenza. This would leave two remaining antiviral medications (oseltamivir and zanamivir) that should still be effective against currently circulating strains of H5N1 virus. Efforts to produce vaccine candidates that would be effective against avian influenza A (H5N1) viruses are under way. However, it will likely require many months before such vaccines could be mass produced and made widely available.

Research suggests that currently circulating strains of H5N1 viruses are becoming more capable of causing disease (pathogenic) in animals than were earlier H5N1 viruses. One study found that ducks infected with H5N1 virus are now shedding more virus for longer periods without showing symptoms of illness. This finding has implications for the role of ducks in transmitting disease to other birds and possibly to humans as well. Additionally, other findings have documented H5N1 infection among pigs in China and H5N1 infection in felines (experimental infection in housecats in the Netherlands and isolation of H5N1 viruses in tigers and leopards in Thailand).In addition, in early March 2006, Germany reported H5N1 infection in a stone marten (a weasel-like mammal). The avian influenza A (H5N1) virus that emerged in Asia in 2003 continues to evolve and may adapt so that other mammals may be susceptible to infection as well.

Notable findings of epidemiologic investigations of human H5N1 cases in Vietnam during 2005 have suggested transmission of H5N1 viruses to at least two persons through consumption of uncooked duck blood. One possible instance of limited person-to-person transmission of H5N1 virus in Thailand has been reported. This possibility is being further investigated in other clusters of cases in Vietnam and Indonesia.

The majority of known human H5N1 cases have begun with respiratory symptoms. However, one atypical fatal case of encephalitis in a child in southern Vietnam in 2004 was identified retrospectively as H5N1 influenza through testing of cerebrospinal fluid, fecal matter, and throat and serum samples. Further research is needed to ascertain the implications of such findings.

Bird Import Ban

There is currently a ban on the importation of birds and bird products from H5N1-affected countries. The regulation states that no person may import or attempt to import any birds (Class Aves), whether dead or alive, or any products derived from birds (including hatching eggs), from the specified countries. For more information, see Embargo of Birds from Specified Countries.

Travel

Updated Information for Travelers about Avian Influenza A(H5N1) is available at the CDC Travelers’ Health Web site. Also see Guidelines and Recommendations - Interim Guidance about Avian Influenza A (H5N1) for U.S. Citizens Living Abroad.

CDC Response

Domestic Activities

• In May 2005, CDC joined a new, inter-agency National Influenza Pandemic Preparedness Task Force organized by the U.S. Secretary of Health and Human Services. This task force is developing and refining preparedness efforts with international, state, local, and private organizational partners to help ensure the most effective response possible when the next influenza pandemic occurs. For more information about the Pandemic Influenza Preparedness Plan of the U.S. Health and Human Services Department and other aspects of this coordinated federal initiative, please visit www.pandemicflu.gov.
• CDC developed the first test approved by FDA for the detection of the H5 viruses that first emerged in Asia in 2003.
• CDC reconstructed the 1918 Spanish influenza pandemic virus to help develop strategies for early diagnosis, treatment, and prevention, if a similar pandemic virus emerged.
• CDC has collaborated with the Association of Public Health Laboratories to conduct training workshops for state laboratories on the use of molecular techniques to rapidly identify H5 viruses.
• CDC is working collaboratively with the Council of State and Territorial Epidemiologists and other partners to assist states with pandemic planning efforts.
• CDC is working with other agencies, such as the Department of Defense and the Department of Veterans Affairs, on antiviral stockpile issues.

International Activities

• CDC is one of four WHO Collaborating Centers and in this capacity provides ongoing support for the global WHO surveillance network, laboratory testing, training, and other actions.
• CDC has worked collaboratively with WHO to conduct investigations of human H5N1 infections in China, Indonesia, Thailand, Vietnam, and Turkey and to provide laboratory diagnostic and training assistance.
• CDC has performed laboratory testing of H5N1 viruses from Vietnam, Thailand, and Indonesia.
• CDC is implementing a multi-million dollar initiative to improve influenza surveillance in Asia.
• CDC has led or taken part in 9 training sessions to enhance local capacities in Asia to conduct surveillance for possible human cases of H5 and to detect avian influenza A H5 viruses using laboratory techniques.
• CDC has developed and distributed a reagent kit for the detection of the currently circulating influenza A H5 viruses.
• CDC has worked with other international and national agencies in Asia to develop a training course for rapid response teams that will be used to help prepare the region to respond to outbreaks when they occur.
• CDC has developed an international program to support surveillance, laboratory capacity, health education, rapid response training, and other activities for avian influenza.

CDC is monitoring the situation closely, along with WHO and other international partners. In addition, CDC continues to work collaboratively with WHO and the National Institutes of Health (NIH) on the development and testing of vaccine seed candidates for influenza A (H5N1).

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NOTE: The World Health Organization (WHO) maintains situation updates and cumulative reports of human cases of avian influenza A (H5N1).

Page last modified April 24, 2006