Avian Influenza (“Bird Flu”): What It Is and Why It's a Concern

Keywords: Avian Flu, Influenza Viruses, Human Influenza Viruses, Antigenic Drift, Antigenic Shift, Types, Subtypes, Strains, Vaccination

While they cannot be predicted, influenza pandemics occur cyclically. The 1918 "Spanish Flu" pandemic killed up to fifty million people worldwide. The recent media focus on avian flu has raised many questions as to what it is, how it works, and what are the real dangers to people. Influenza is divided into types A, B and C. Humans can be infected with any of these types. Type B viruses are normally only found in humans. While these viruses can cause serious illness, they have not caused pandemics. Type C viruses cause only mild illness in humans. Type A viruses are quite different, however. Type A viruses have subtypes that are classified by the variations in the hemagglutinin [HA] and neuraminidase [NA] proteins of the type A virus. The strains are named for these variations such as H7N3, H7N2 or H5N1, the current strain that is causing so much alarm. The natural hosts for type A viruses are wild birds – hence, the common name, “bird flu.”

Influenza viruses are continuously evolving through the processes of either antigenic shift or antigenic drift. Antigenic drift occurs when an influenza virus changes into a new strain over the course of several gradual mutations. Antigenic shift is a sudden, major change that produces a new subtype of influenza virus that has never been seen before. This occurs through direct animal-to-human transmission or through the mixing of animal and human influenza virus genes. If an antigenic shift introduces a new subtype of influenza A virus that causes serious illness in humans and can easily spread from person to person, it may result in a pandemic. H5N1 is a new subtype that causes serious illness and death in humans. If the virus were to evolve to retain its capacity to cause serious illness and gain the capability to spread easily from person to person, it could cause a pandemic . In addition to general information, these resources provide facts on planning and preparedness.

This page was developed by Amanda Bauer, a graduate assistant in the Science Library.

Selected Internet Resources – core sites

CDC Avian Influenza Main Page: http://www.cdc.gov/flu/avian/

The Center for Disease Control and Prevention monitors and provides information on public health and safety in the United States. They provide a range on information on Avian Influenza (H5N1), including how it is spread, what current risks Americans face, and how this flu is different from the usual seasonal influenza.

PandemicFlu.gov: http://www.pandemicflu.gov/

PandemicFlu.gov is the "… official U.S. government Web site for information on pandemic flu and avian influenza" sponsored by U.S. Department of Health & Human Services. Information is organized by topic: ex, outbreak surveillance, planning and response activities, travel and transportation issues, health and safety, and research activities.

World Health Organization Avian Influenza Main Page: http://www.who.int/csr/disease/avian_influenza/en/

The World Health Organization is the United Nations' specialized organization dedicated to ensuring the highest possible mental, physical and emotional health of all peoples. The WHO Avian Influenza page gives public health information on Avian Influenza that focuses on advice to the public, current information, and preparedness measures.

Selected Internet Resources – other sites

Avian Flu Timeline from Nature: http://www.nature.com/nature/focus/avianflu/timeline.html

This timeline from Nature mentions past influenza pandemics before continuing on to discuss H5N1. The timeline discusses details of the progression of Avian Influenza from its identification on May 21, 1997 to the detection of the virus in Europe in October 2005.

HHS Pandemic Influenza Plan: http://www.hhs.gov/pandemicflu/plan/

A plan outlined by the U.S. Department of Health and Human Services to respond to a pandemic outbreak, should one occur. The plan includes detail about the interaction between federal, state and local authorities for handling a pandemic outbreak of Avian Flu.

International Travel Pages sponsored by the Bureau of Consular Affairs (U.S. Department of State), Avian Flu Fact Sheet: http://travel.state.gov/travel/tips/health/health_1181.html

This fact sheet gives an overview of Avian Influenza for travelers. The site includes information about travel warnings and precautions for travelers in Avian Influenza-infected areas. It also includes information on what services American Embassies and Consulates may be able to provide for Americans abroad.

National Institute of Allergy and Infectious Diseases, "Focus on the Flu” http://www3.niaid.nih.gov/news/focuson/flu/

NIAID has information on preventing, diagnosing and treating influenza viruses, as well as the steps researchers are taking to prepare for a pandemic. The site includes graphic representations of viruses, antigenic drift and shift, and developing vaccines.

NYS Department of Health fact sheet on Influenza and Avian Flu http://www.health.state.ny.us/diseases/communicable/influenza/

The NYS Department of Health gives general information on influenza and links to additional information on Avian Influenza. The site includes links to weekly reports on seasonal influenza activity in the state of New York.

NYS Department of Agriculture and Markets - Avian Flu: http://www.agmkt.state.ny.us/AI/AvianFlu.html

The NYS Department of Agriculture and Markets's page on Avian Influenza discusses the virus in terms of how it could affect the agricultural industry. It includes detailed information on the virus, discussion of the department's ongoing surveillance for avian influenza and information on how to prevent infection and control the spread of the disease among commercial poultry.

Periodical Articles (general interest and newsletters):

Adler, Jerry, Underwood, Anne, Hosenball, Mark, Brant, Martha, & Wingert, Pat. (2005) The Race Against Avian Flu. Newsweek. 146 (16), 38-39.

This article gives a substantial overview of H5N1. The virus is compared to the Spanish Flu of 1918. Despite some similarities, medical and social differences between 1918 and now may provide a much better defense even against a more deadly strain.

"Avian Influenza and the Significance of Us Transmission to Humans--Information from WHO" (2005, October) Journal of Environmental Health (68) 3, 41-42.

This article provides a substantial overview of H5N1 in birds, how influenza viruses change and treatment of H5N1. Additionally, it provides a brief timeline of the disease's presence in humans as well as what measures can be taken to mitigate a pandemic.

Chatterjee, Patralekha. (2005, December 17) Hong Kong battens down the hatches. Lancet, 366 (9503), p2073-2074.

This article discusses preparations made in Hong Kong to deal with a possible outbreak of H5N1. Despite best efforts, the region's proximity to centers of emerging infectious diseases continues to create challenges for medical professionals. The article also discusses the inadequate influenza vaccine supply in Hong Kong. Hong Kong's Centre for Health Protection is working to strengthen disease reporting systems and increase Hong Kong's preparedness for infectious disease outbreaks.

Fuentes, Annette. (2005, November 11) When public health outweighs profits. USA Today, pg. 15a.

Roche has come under pressure to increase production of Tamiflu due to the stockpiling for the drug by public health agencies. This article discusses Roche's response to this pressure as well as the ethical questions involved in selling Tamiflu if there were an avian flu pandemic.

Knox, Noelle. (2005, November 8) 'Matter of time' before bird flu pandemic strikes, WHO says. USA Today, Pg. 11a.

The World Health Organization (WHO) has announced that it is only a matter of time before a strain of avian flu acquires the ability to be transmitted from human to human and begins a pandemic. The article discusses past pandemics as well as proposed plans to prepare for the next pandemic.

Schmit, Julie. (2005, November 14) Poultry farm tactics may thwart bird flu. USA Today, pg. 01a.

Precautions to prevent poultry from coming into contact with wild birds will help prevent birds and humans from coming into contact with H5N1. These precautions include keeping poultry indoors and stringent rules for anything entering or leaving the farm. Biosecurity measures coupled with the unlikelihood of North American wild birds becoming infected with the virus means that current risk of infection is very low in the United States.

"When the chickens come home to roost: The despair, and the hope, surrounding Turkey's bird-flu outbreak" (2006, January 14) Economist, 378 (8460), p54-55.

This article discusses outbreak of H5N1 in Turkey. Fifteen people were diagnosed with the disease with at least two confirmed deaths from the avian flu. Over one quarter of Turkey's provinces have reported having infected birds. Despite a higher infection rate, there have been an unusually high number of mild cases of the flu. This may be a positive sign, however, Turkey still faces numerous challenges in dealing with infected birds.

Yu, Hongjie, et al. (2006, January 1) The first confirmed human case of avian influenza A (H5N1) in Mainland China. Lancet, 367 (9504), p84.

This case study discusses the first confirmed case of avian influenza A in mainland China. A twelve year old girl in Hunan became ill on October 8, 2005. Her brother also contracted the virus. The case study discusses how the children contracted H5N1, their symptoms, and the procedures followed in response to their illness.

Periodical Articles (semi-technical and technical):

Apisarnthanarak, Anucha, et al. (2005, January 15) Seroprevalence of Anti-H5 Antibody among Thai Health Care Workers after Exposure to Avian Influenza (H5N1) in a Tertiary Care Center. Clinical Infectious Diseases 2, p. e16-e18.

Researchers compared serum samples from twenty-five health care workers that had been exposed to patients with H5N1 to samples from twenty-four health care workers that had not been exposed. There was no serologic evidence of anti-H5 antibody reactivity in either group.

Condon, Christopher (2005, November 12) A vaccine in 50 days? Lancet 366 (9498) pg.1686.

Utilizing an older vaccine production method, Hungarian scientists believe they can produce an avian influenza vaccine in fifty days rather than the standard six month production time required for current vaccine production. The method uses whole inactivated virus in conjunction with an adjuvant to strengthen the long-term efficacy of the vaccine.

Donis, Ruben O. (2005, October) Evolution of H5N1 Avian Influenza Viruses in Asia Emerging Infectious Diseases 11 (10) p1515-1521.

This technical article discusses how H5N1 has been tracked and analyzed in Asia. Analysis of H5N1 samples showed two distinct clades of the virus. Additionally, there is no indication that the virus had undergone reassortment with human influenza viruses. The study also examines H5N1 treatments to determine which are most effective.

Guan, Yi and Chen, Honglin. (2005, October 1) Resistance to anti-influenza agents. Lancet (366) 9492, p1139-1140.

This article examines influenza resistance to anti-influenza agents. Influenza infection can be controlled through either prevention or treatment with antiviral drugs. This article examines why influenza viruses are so adaptable as well as statistics on resistant rates to anti-virals currently in use.

"Harmless Virus May Aid in Knocking Out Deadly Bird Flu" (2005, December) Journal of Environmental Health, 68 (5) p48.

This article reports that the use of a adenovirus as a delivery vehicle may help prevent an human outbreak of bird flu. Modern flu vaccines utilize proteins from fertilized chicken eggs. This process can take months to produce a new vaccine, which makes it difficult to keep pace with virus mutations. Avian flu threatens both humans and the poultry used to produce influenza vaccines. Adenovirus-based vaccines could be made more quickly and without relying on chicken proteins.

Mims III, Forrest M. (2005, December) Avian Influenza and UV-B Blocked by Biomass Smoke. Environmental Health Perspectives, 113 (12), pA 806.

This article proposes controlling avian influenza by reducing smoke pollution in Asia. Since ultraviolet-B radiation will kill influenza viruses, a reduction in smoke pollution would allow for an increase in the natural levels of UV-B that would help destroy the virus in outdoor air that is exposed to sunlight.

Osterholm, Michael T. (2005, July) Preparing for the Next Pandemic. Foreign Affairs 84 (4), p24-37.

This article puts influenza in the context of other infectious diseases. It is estimated that an influenza pandemic could cause five times as many deaths as the cumulative number of documents AIDS deaths. In the "Spanish Flu" pandemic, most deaths were due to cytokine storms which caused acute respiratory distress syndrome (ARDS). H5N1 has shown to cause similar cytokine storms in human cases. This article segues into a discussion of the economic impact of a pandemic, as well as proposed preparedness measures.

Selim, Jocelyn (2005, October) Can Gold Stop Avian Flu? Discover pg 13.

PowerMed is developing a DNA-based vaccine for avian flu. Gold particles coated with avian flu are sprayed onto human skin using high-pressure helium. In initial trials this method has produced immunity comparable to traditional vaccines.

Updated February, 2006

Amanda Bauer
February, 2006