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Will Avian Flu be the Next Pandemic?

Edited by: Stephanie Wallner, M.S., Mary Schroeder, M.S., R.D, Pat Kendall, Ph.D., R.D., Colorado State - Fall 2006

Increasing attention has been placed in recent months on the potential development of a pandemic (large scale or world wide epidemic) caused by avian influenza, more commonly known as "bird flu." Avian (bird) flu is an infection caused by influenza viruses that occur naturally among birds. Wild birds worldwide carry the viruses in their intestines, but usually don't get sick from them. Avian flu is very contagious among birds, and can make some domesticated birds, including chickens, turkeys, and ducks, very sick. Domestic birds become infected through direct contact with waterfowl or other poultry that have the illness, or by contact with contaminated surfaces, water, or feed.

Avian flu generally refers to type A influenza viruses in birds, and has two main forms - a "low pathogenic" form (LPAI) and a "high pathogenic" form (HPAI). The low pathogenic form causes very mild symptoms in birds, such as decreased egg production. The high pathogenic form, however, is more serious, can spread rapidly through flocks, and is often fatal with death rates reaching up to 90-100% in some infected flocks.

The influenza virus that has caused so much recent concern is the H5N1 virus, which occurs mainly in birds, but has adapted so that it has the ability to infect humans and cause severe illness. Between 2003 and 2004, outbreaks of avian influenza H5N1 killed more than 100 million poultry across eight countries in Asia. While the risk for transfer of avian flu to humans is relatively low, more than 150 human cases, half of which have ended in death, have been reported worldwide since human cases of avian flu first appeared in Southeast Asia at the end of 2003. Most of these cases have been caused by direct or close contact with infected domestic poultry or contaminated surfaces; however, a few cases of human-to-human spread of H5N1 also have been seen.

So far, the spread of H5N1 virus among humans has been rare and has not continued beyond one person. Still, researchers studying avian flu are worried that the virus could adapt as influenza viruses often do, and could gain the ability to spread much more easily among humans, potentially triggering a worldwide outbreak of the disease in a population with no developed immune protection. For this reason, vaccines are being developed and clinical trials are ongoing.

Symptoms and Transmission of Avian Flu

Thus far, avian flu has not been seen in humans in the United States. Symptoms range from typical flu-like symptoms (fever, cough, sore throat, and body aches) to more serious eye infections, pneumonia, and acute respiratory distress. The greatest risk of exposure to the avian flu virus is through the handling and slaughtering of live infected poultry. Transmission is also possible through surfaces contaminated by poultry feces. Poultry products, however, are safe to eat as long as proper preparation and consumption precautions are taken.

Prevention

The World Health Organization (WHO) and Food and Agricultural Organization (FAO) recommend the following precautions to prevent avian flu:

1. If you come across any dead or sick birds, do not touch them.
2. Cook all poultry to an internal temperature of 70ºC (180ºF). While the virus is not killed by refrigeration or freezing, it is destroyed by conventional cooking. Cooked poultry should have no pink spots.
3. Cook eggs until the white and yolk are firm. Because eggs can contain H5N1 virus both on the outside (shell) and inside (whites and yolk), eggs from areas with H5N1 outbreaks in poultry should not be consumed raw or partially cooked (runny yolk). While there have been no outbreaks of H5N1 in poultry in the U.S., cooking eggs thoroughly is always a good idea to prevent the spread of salmonella and any other bacteria or viruses that may be present.
4. Carefully avoid cross-contamination during food preparation. Drippings or juice from raw poultry should never be allowed to come into contact with prepared foods, and surfaces used to prepare raw meat should be cleaned thoroughly with soap and hot water.
5. Wash hands thoroughly with soap and hot water after handling raw poultry to prevent the spread of any viruses or bacteria.

The following websites provide more information on this emerging health concern:

• http://www.aphis.usda.gov/lpa/issues/avian_influenza/index.html
• http://www.cdc.gov/flu/avian/
• http://www.pandemicflu.gov/
• http://www.who.int/csr/disease/avian_influenza/avian_faqs/en/print.html

Sources:

1. CDC. Key facts about avian influenza and avian influenza A (H5N1) virus. November 25, 2005.
2. WHO. Avian influenza frequently asked questions. December 5, 2005. available at: http://www.who.int/csr/disease/avian_influenza/avian_faqs/en/print.html
3. UPI. Report: Avian flu may not show symptoms. Jan 19, 2005.

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