Information on Avian Influenza

About Avian Influenza
Avian influenza (AI) is caused by the Influenza A virus and can affect all bird species. It is believed that wild birds, especially migratory waterfowl, carry the virus and they may or may not show signs of having the virus. The problems arise when the virus infects bird species such as chickens and turkeys.

The different subtypes for the AI virus are assigned based on surface antigens on the virus HA and NA subtypes. H stands for Hemagglutinin of which there are 15 types. N stands for Neuraminidase of which there are 9 types. In theory, there are 135 different subtypes of the virus that cause Avian Influenza. The more severe viruses with higher mortality rates for birds are called highly pathogenic Avian Influenza (HP AI) and the less severe viruses that cause milder illnesses are low pathogenic Avian Influenza (LP AI). Although most H5 and H7 viruses are low path, so far highly pathogenic strains have only arisen from H5 and H7 virus types. Since viruses are made up of genetic material and undergo mutations, it is possible for the viruses to mutate from a LP AI to a HP AI form. For that reason, the detection of any AI outbreak requires that producers, veterinarians, and government officials work quickly to contain and control the virus.

The uses, treatments, and side effects of the antibiotic AmoxilAmoxicillian to treat bacterial infections: pneumonia, tonsillitis, bronchitis, ear infections, urinary tract infections. 

History of Highly Pathogenic AI Outbreaks
The last outbreak of highly pathogenic avian influenza (HP AI) affecting the layer industry in the US was in 1983-84 when H5N2 was found in Pennsylvania and Virginia. There was a small H5N2 HP AI outbreak in Texas in 2004 in broilers. The AI strain in Texas was not clinically highly pathogenic in the birds; however, it was genetically similar to other highly pathogenic strains and was classified as HP AI. H5N2 has not been associated with any human illnesses.

In recent years, outbreaks of HP AI have occurred in other countries including H5N1 in Hong Kong in 1997, H7N7 in the Netherlands and Belgium in 2003, and H7N3 in British Columbia, Canada in 2004. An outbreak of H5N1 HP AI has been ongoing in Asia for several years and has recently been detected in Eastern Europe. The concerns about the ongoing Asian outbreak are related to the avian virus mutating and causing a widespread outbreak of influenza in humans. At this time, the H5N1 virus does not easily infect humans and the H5N1 virus does not exist in the United States.

Are eggs safe to eat?
Yes, eggs are safe to eat. If egg laying hens develop AI, one of the first symptoms is that they stop laying eggs. After the virus is discovered, the farm is quarantined. Table eggs are washed and sanitized before being sold so that if virus were present on the shell, it would be inactivated. In past outbreaks of LP AI, virus particles have never been isolated from eggs. In high path outbreaks, virus particles have been isolated from embryos and it is possible that virus particles could be on the egg shell surface. Due to the nature of AI viruses, the virus would not be able to replicate in a commercial shell egg.

In laboratory studies, scientists artificially put the virus into eggs and then measured temperatures required to destroy the virus. The AI virus is destroyed at temperatures required for pasteurization and cooking. Even if the influenza A virus made it into an egg, the virus would not survive the cooking process. This ensures that properly cooked eggs are safe to eat.

Does Avian Influenza affect humans?
It is extremely rare for humans to experience health problems due to AI; however, there have been a few documented cases when humans have become ill due to AI. Here in the US, the only known illnesses have been conjunctivitis of the eyes when people handling sick birds have then touched their eyes. In 1997, it was reported in Hong Kong that eighteen people became ill and six people died after contracting H5N1 HP AI after direct contact with sick birds. In 2003, one fatal human case was reported in the Netherlands due to H7N7, involving a veterinarian with prolonged direct contact with infected birds. The outbreak of highly pathogenic H5N1 in Asia has been associated with numerous human illnesses and approximately 60 deaths over a three year period. The outbreak in British Columbia, Canada in 2004 was also associated with some cases of human illness when there was close contact with sick birds. It is important that farm workers and animal health professionals use proper protective clothing and equipment when working with birds infected with AI or other diseases.

Control Measures for Egg Facilities

  • The importance of biosecurity measures cannot be over emphasized.
  • Protect domesticated (or commercial) birds from contact with wild and migratory birds.
  • Restrict the farm and facilities to essential personnel only.
  • Monitor all visitors and restrict access when necessary.
  • Provide clean or disposable clothing and shoe coverings to employees and visitors and recommended personal protective equipment.
  • Sanitize all equipment and vehicles when entering and leaving the farm especially if there has been contact with live bird markets.
  • Protect water and feed sources from possible contamination.
  • Implement the recommended biosecurity practices for poultry production facilities.
  • Order and implement an interactive CD on biosecurity plans available free from the US Poultry and Egg Association (
For More Information on Avian Influenza

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Prepared by Hilary Shallo Thesmar, PhD, RD, Director, Egg Safety Center and Donald J. McNamara, PhD, Executive Director, Egg Nutrition Center, Washington DC. For additional information or questions please contact Dr. Thesmar at 202 833-8850 or