Avian Influenza: An Infectious Disease


            Avian influenza is a global health problem.  This disease can easily claim the lives of many bird species.  It is caused by a virus which is transmitted through feces and saliva.  The problem, however, is no longer limited to birds.  Some subtypes of the avian influenza virus can also affect humans.  Humans can also be infected through direct exposure to avian feces and saliva.  Not only does avian influenza prove harmful to humans, but it is also deadly.  Though avian influenza remains a health concern, there are ways to prevent the spread of this disease.

Avian Influenza: An Infectious Disease

Avian influenza has been a worldwide health concern.  Infected species of birds easily spread the disease to other avian species through migration.  The problem is exacerbated by the fact that the disease which affects birds also affects humans.  This disease had already proven to be fatal to both birds and humans.  This research paper aims to discuss the important details about avian influenza: what causes it, how it is transmitted and how it can be prevented.

            Influenza is a communicable disease which affected humans for a long time (Alexander, Capua & Brown, 2005).  Since ancient times, it had been the cause of many epidemics.  Influenza viruses are characterized by RNA genomes and do belong in the Orthomyxoviridae family.  These viruses are categorized into three types: A, B and C.  It is the influenza-A viruses which are responsible for the infection of animal species.  Animals susceptible to acquiring these viruses include birds, pigs, horses, sea mammals and humans (Alexander et al., 2005).

            Avian influenza, also known as bird flu, is an infectious animal disease which resulted from viruses that usually affects birds and, on rare instances, pigs (World Health Organization [WHO], 2005).  The viruses of avian influenza were said to have initially affected pigs (“Avian Influenza,” 2007).  These viruses, combined with viruses of pig influenza, create a new virus.  The new virus would eventually have the capacity to infect humans, a virus that can easily be transmitted from one person to the next.  Prior flu epidemics have originated through this process (“Avian Influenza,” 2007).

            As the name suggests, avian influenza is a disease which affects birds (Center for Disease Control and Prevention [CDC], 2007).  It must be noted that influenza viruses are natural among the avian species.  All over the world, birds have those viruses on their intestines; despite this, these viruses do not make the said birds ill.  In contrast, avian influenza is highly infectious; not only does it make birds ill, but it is also strong enough to kill them.  Those which are affected by avian influenza are the domesticated birds, such as chickens and turkeys (CDC, 2007).

            Birds which have been infected with avian influenza release the virus through saliva, feces and even nasal secretions (CDC, 2007).  Healthy birds could be infected when they come into contact with secretions and feces which carry the virus.  As for domesticated birds, there are two ways in which they could acquire the virus.  The first one is through direct exposure to infected birds.  The second one is through surface contact; birds become infected when they come into contact with either contaminated surfaces, bird feeds or water (CDC, 2007).

            In the case of domestic poultry, when birds are infected with the avian influenza viruses, there are two diseases which come into the fore (CDC, 2007; WHO, 2005).  These diseases are differentiated by “low and high extremes of virulence” (CDC, 2007; WHO, 2005).  The first disease is characterized as “low pathogenic”; this disease mildly affects the birds (CDC, 2007; WHO, 2005).  A decrease in the production of eggs and the presence of ruffled feathers are only two of the symptoms of the low pathogenic disease.  In contrast, the high pathogenic disease has much more severe effects.  Not only does it infect at a quicker rate, but it also attacks several internal organs at once.  The death rate of the high pathogenic form could be 100 percent; death usually occurs within 2 days (CDC, 2007; WHO, 2005).

            Influenza-A viruses have multiple subtypes (CDC, 2007).  Influenza-A virus has the hemagglutinin (H) and neuraminidase (N) proteins.  The various subtypes are the result of the changes in these proteins on the virus’ surface.  According to the World Health Organization (2005), there are 16 H and 9 N subtypes in the influenza-A virus.  The viruses which are of the H5 and H7 subtypes are the only ones known to result in the high pathogenic disease (WHO, 2005).  Nonetheless, not every virus of the H5 and H7 subtypes is highly

pathogenic.  Also, not every virus will result in poultry disease (WHO, 2005).  It is important to note that every recognized subtype of influenza-A are carried by birds (CDC, 2007).

            Though the viruses of influenza-A are usually found in birds, it does not mean that humans cannot be infected with these (CDC, 2007).  The risk of acquiring avian influenza is actually low since these viruses are not known to infect humans.  Nonetheless, there had been recorded cases wherein humans were infected with some avian influenza subtypes.  It was in 1997 when the first case of the human infection of the avian influenza virus occurred (“Avian Influenza,” 2007).  It happened in Hong Kong, while in the midst of an avian flu epidemic.  From the 18 people who were infected, nine were killed by the virus (Department of Human Services, 2005).

            “Human influenza virus” is the name attributed to the subtypes which widely infect humans (CDC, 2007).  There are three recognized subtypes of human influenza viruses that are known to have spread among humans: H1N1, H1N2 and H3N2.  There is a great possibility that several genetic parts of the human influenza viruses may have originated from birds.  Because these viruses are continuously in the process of changing, it is likely that the viruses may eventually evolve to infect humans as well (CDC, 2007).

            There is a subtype of the influenza-A virus which proves most harmful to humans.  It is called the H5N1 virus (CDC, 2007).  This subtype is not only infectious among bird species, but it is also fatal.  Generally, the H5N1 subtype does not affect humans, though there have been reported cases of human infections due to this virus.  In fact, among the avian influenza viruses which have also affected humans, H5N1 is responsible to the extreme human cases as well as several fatalities.  The aforementioned human deaths in Hong Kong caused by avian influenza were caused by H5N1 (“Avian Influenza,” 2007).

            The H5N1 virus presents two major human health concerns (WHO, 2005).  The first one is the severe disease caused by the transmission of the virus from poultry to humans.  While seasonal influenza may only cause minor respiratory problems, influenza caused by H5N1 has more severe effects on humans.  The patient’s health declines at a rapid rate, and death is very much likely.  Common effects of this virus include pneumonia and multiple organ failure.  The second health concern is the possible mutation of the virus that would allow it to be easily transmitted from one person to the next.  Such mutation can start a pandemic, which would surely be detrimental to humans (WHO, 2005).

            Humans become infected with avian influenza the same way that birds are infected with this disease.  It is only through direct contact with infected birds and contaminated materials wherein one can acquire the disease (WHO, 2005).  As was mentioned earlier, the virus is released from infected birds through excretions and secretions.  Hence, the only way a human can be infected is either through direct contact to the sick birds or to the materials that have been tainted with contaminated feces or saliva.  Most recorded cases of human infections have happened in homes wherein families own flocks of poultry; these flocks usually free to roam around homes and also public places.  Because infected birds release vast amounts of the virus in feces, their free roaming can cause contamination of a greater area (WHO, 2005).

            Though avian influenza does pose a serious health threat, it must be known that it can still be prevented, provided that necessary precautions are taken.  Biosecurity is the name of the precautions taken to guarantee the health of livestock through efforts of disease prevention (Canadian Food Inspection Agency [CFIA], 2008).  To effectively prevent avian influenza, disinfection is necessary (CFIA, 2008).

            Disinfection plays a key role in eliminating avian influenza viruses.  When one speaks of disinfecting, the following must be considered: “steam cleaning, fumigation and use of chemical disinfectants” (CFIA, 2008).  Before disinfectants can be used, it is crucial that the objects to be disinfected are thoroughly washed.  It is only with clean surfaces when disinfectants truly work.  The disinfectant used must be the most appropriate for the product.  The instructions of applying disinfectant must be followed to the letter.  Lastly, allow the disinfectant must be allowed to take effect before again using the product (CFIA, 2008).

            Bird handlers and poultry raisers can also prevent avian influenza if they are aware of its symptoms.  These are some of the symptoms of avian influenza in birds: lethargy and lack of appetite, decrease in egg production, swelling of certain body parts, colds and cough, as well as diarrhea (CFIA, 2008).  If the birds exhibit any of these signs, bird handlers and poultry raisers must immediately contact the authorities (CFIA, 2008).

            Bird owners can prevent avian influenza through cleanliness and other safety precautions.  Access to poultry farms must be limited (CFIA, 2008).  This would prevent the spread of diseases.  However, if there are visitors, there are some things to consider.  First, clothing must be supplied to the visitors.  These clothes must be worn within the premises.  Second, even footwear must be provided to the visitors.  If this cannot be done, footwear must be thoroughly washed and disinfected.  Foot baths must also be installed; these must contain disinfectants.  Third, visitors must wash their hands before entering the premises.  Fourth, vehicles must be parked at a minimum distance of 30 meters away from the farm.  Before vehicles can enter the premises, disinfectant must be sprayed to the vehicles.  Special attention must be paid to the tires and undercarriage (CFIA, 2008).  These are some of the ways in which avian influenza can be prevented.

            Avian influenza is indeed a serious health threat.  It is a dangerous disease that not only severely affects birds but it also           proves fatal to avian species.  Furthermore, avian influenza also affects humans.  It can aggressively deteriorate one’s health, eventually leading to death.  Despite this, it can still be prevented.  There are measures that can be taken to eliminate the viruses which cause this disease.  It is important that before the situation gets worse, the disease must be prevented.


Alexander, D.J., Capua, I. ; Brown, I.H. (2005). Avian influenza viruses and influenza in humans. In R. Schrijver ; G. Koch, Avian Influenza: Prevention and Control. New York: Springer.

Canadian Food Inspection Agency. (2008). Avian Influenza: Biosecurity.  Retrieved August 5, 2008, from http://www.inspection.gc.ca/english/anima/heasan/disemala/avflu/bacdoc/prevente.shtml

Centers for Disease Control and Prevention. (2007). Avian Influenza (Flu). Retrieved August 5, 2008, from http://www.cdc.gov/flu/avian/gen-info/facts.htm

Department of Human Services. (2005). Avian influenza: know when the sky is falling. CD Summary, Vol. 54 (26).  Retrieved August 5, 2008, from http://www.oregon.gov/DHS/ph/acd/flu/zooflu.shtml

The New York Times. (2007).  Avian Influenza.  Retrieved August 5, 2008, from http://health.nytimes.com/health/guides/disease/avian-influenza/overview.html

World Health Organization. (2005). Avian Influenza Frequently Asked Questions.  Retrieved August 5, 2008, from http://www.who.int/csr/disease/avian_influenza/avian_faqs/en/#present

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