Health Impact of Avian Flu (Bird Flu)

Avian Flu is an important disease of domestic poultry that is spread by a Type A Influenza Virus.  Highly Pathogenic Avian Flu has caused severe epidemics that have devastated the poultry industries in Southeast Asia, China, and Hong Kong over the last year.  The subtypes causing such terrible outbreaks are viruses that are of subtypes H5 and H7- these cause Highly Pathogenic Avian Influenza.  Millions of birds (turkeys, chickens, ducks, geese, quail) have been culled to further minimize the spread of the disease.    

In addition to devastating poultry industries and killing millions of birds, avian flu has the potential to create even more destruction in humans.  The Avian Flu outbreak (Avian Flu Virus Subtype H5N1) led to the first reported case of avian flu being passed from birds to humans.  In 1997, eighteen people were hospitalized with Avian Flu, where six of them tragically died to severe respiratory problems.  Late 2003 and early 2004, another avian flu outbreak occurred in Southeast Asia. 

The fear of many health organizations and governments around the world is that the avian flu virus and human flu virus may evolve into a deadly new flu strain that can cause a worldwide pandemic.  If an animal (humans or pigs) has both Avian and Human Flu viruses in their system, then both types of viruses may interact with each and exchange genetic information.  The new strain of flu virus may potentially have the ability to be transmitted more effectively by humans to other humans (from the Human Flu Virus).  Also, the potential new strain of flu virus will have different surface proteins, which may render useless any vaccines and also any built-up immunity.   

The Fear of a Human Pandemic

We all know that there is a “Flu Season”.  Routine annual outbreaks of influenza in both humans and animals are caused by minor changes in the surface proteins of the viruses.  Minor adaptations allow the viruses to elude the immunity that some individuals have developed from previous infections or in response to vaccinations.  So, during routine influenza outbreaks, some people become ill while others do not.

However, when a major change can occur when viruses radically change their surface proteins.  This can occur when different Influenza viruses (i.e. Avian and Human Influenza Viruses) rearrange and swap their genetic material with each other.  If a new strain of Flu virus is generated, then it may be devastating to the human population, as their immune systems have no defense against the new flu strain.  If this new virus strain also has the capacity to spread from person to person, then the potential for pandemic spread is greatly enhanced.

In the context of Avian Flu, since humans are able to contract the Avian Flu virus, then there is a probability that the Avian Flu virus and the Human Flu virus can interact and produce a deadly new strain.  Also, pigs have been found to be able to contract both Human and Avian Flu viruses, thus potentially serving as a “mixing vessel” that can produce a new strain. 

So far, the avian flu viruses that have been transmitted to humans are of subtypes H5 and H7.  The subtype that has attracted the most attention is H5N1.  It is this subtype that has affected the severest outbreaks in Hong Kong and Southeast Asia that have led to the deaths of human lives.  So far, there is no evidence that the avian flu virus has developed the capacity to be spread from humans to humans.  Although the prevalence of H5N1 around the whole of Eastern Asia greatly increases the risk that it may evolve to a point where transmission between people are possible. 

In an interview conducted with the Times Newspaper, a leading avian flu scientist Dr. Yi Guan said, “Continued, extensive exposure of the human population to H5N1 viruses increases the likelihood that the viruses will acquire the necessary characteristics for efficient human-to-human transmission through genetic mutation or reassortment with a prevailing human influenza.”  Guan and his research team had published a revealing paper in the prominent journal, Nature, that traced the genetic origins of the H5N1 strain back to a precursor virus, which is also thought to have given rise to a flu strain that caused a human outbreak in Hong Kong in 1997.

In fact, most public health organizations are not optimistic about the outcome of Avian Flu.  Many experts fear that another flu pandemic is just a matter of time, and that Southeast Asia is likely to be its epicenter.  In fact, The World Health Organization has recently issued a dramatic warning that Avian flu will trigger an international pandemic that could kill up to seven million people – and that’s their “best case” scenario.  Said Klaus Stohr of the WHO Global Influenza Program,  “There is no doubt there will be another pandemic."

There have been three pandemics in the 20th century, all spread worldwide within a year of being detected.  The Asian flu pandemic of 1957 claimed nearly 70,000 lives in the United States and one million worldwide after spreading from China.  In 1968, the Hong Kong flu pandemic is also said to have killed around one million.  Both pandemics were believed to be mutations of pig viruses.  The worse flu pandemic occurred in 1918-19.  The “Spanish Flu” pandemic killed as much as 50 million people worldwide.  It is widely believed that the Spanish Flu virus was caused by a hybrid flu strain that evolved from Avian and Human Flu viruses.