Avian Influenza, also known as bird flu, is a zoonotic disease with several different subtypes that affect mostly other birds, but few can be transmitted to humans. The most prevalent avian influenza virus in humans is the highly pathogenic Avian Influenza A (H5N1) virus, which has caused over 380 confirmed cases in 15 countries (Rabinowitz, 2010). Majority of cases have been transmitted via bird-to-human, with rare cases of human-to-human transmission.
Continued exposure to the virus not only poses the threat of ongoing morbidity and mortality, but also the threat of H5N1 being able to adapt and change allowing sustained human-to-human transmission.
(Rabinowitz, 2010). Human exposure to H5N1 begins with the natural host for the virus, wild birds, which is then transmitted to domestic birds, and then finally reaching humans as a host. Starting with wild birds, most commonly waterfowl, the virus lives in the intestines and is shed through fecal matter, saliva, and nasal secretions.
Most wild birds are resistant to infections associated with avian influenza A.
Wild birds are exposed to the virus when they come into contact with contaminated nasal, respiratory, or fecal material from infected birds, most commonly fecal to oral transmission (Korteweg & Gu, 2010). Transmission to domestic birds, mainly poultry, can occur with direct contact with infected birds or indirect exposure through contaminated dirt, cages, water, and feed. Domestic birds have little to no resistance to the virus and suffer serious health issues, often resulting in death (Influenza Viruses, 2005).
In the case a human is infected with H5N1, transmission routes are either through direct contact or indirect contact.
Direct contact consists of people holding, catching, hunting, or playing with unknowingly infected birds. Slaughtering, defeathering, processing and preparing poultry for consumption are other ways a person can be infected through direct contact. Examples of indirect contact are touching contaminated surfaces and materials, swimming in or washing with contaminated water, living and working in areas with contaminated air, or ingesting the active virus in contaminated food (Rabinowitz, 2010).
There is little evidence supporting human-to-human transmission and few cases have been confirmed. From what is known, intimate and close contact with infected individuals are possible routes of transmission (Avian Influenza A, 2005). The potential for H5N1 to develop into a strain easily transmissible from person to person in a sustained matter poses as a threat for a possible pandemic infection (Influenza Viruses, 2005). Signs and symptoms associated with H5N1 are much like those of the more common seasonal flu virus; fever, headache, sore throat, cough and rhinitis.
Other symptoms include conjunctivitis, gastrointestinal complications, shortness of breath, lower respiratory problems, rhinorrhea, myalgia, diarrhea, leukopenia, lymphophenia, impaired liver function, renal impairment, and prolonged blood clotting (Apisarnthanarak, 2004). As of March 2011, over 530 confirmed human cases of H5N1 have been found in 15 countries since 2003 (WHO image 1), 85% occurring within Asian countries. Countries with the highest prevalence rates are Vietnam, Egypt, and Indonesia. Median age of those infected is 18 years old (Korteweg & Gu, 2010).
A contributing behavioral factor associated with the disease being more prevalent in children and young adults is the age groups participation in the slaughter, defeathering and cooking of poultry (Smallman-Raynor & Cliff, 2008). H5N1 had not been seen in humans prior to 1997, first presenting itself in China. The virus was then seen again in humans in 2003, in Vietnam and again in China. By 2007, H5N1 had spread to Cambodia, Indonesia, Azerbaijan, Djibouti, Egypt, Iraq, Turkey, Laos, Myanmar, Nigeria and Pakistan (Smallman-Raynor & Cliff, 2008).
The following public health organizations have been working closely together to track and control recent outbreaks: World Health Organization (WHO), Organization for Animal Health (OIE), and Food and Agriculture Organization (FAO) (Smallman-Raynor & Cliff, 2008). WHO has been responsible for providing recent data and statistics regarding H5N1 in humans. Avian Influenza is covered by GAR, WHO’s Global Outbreak Alert and Response Network, which is responsible for monitoring and keeping surveillance on the disease. OIE is responsible for reporting recent data relating specifically o outbreaks of avian influenza in animals. FAO, working collaboratively with OIE and WHO, “sets the context for national and regional strategies, policies, programs and projects designed to control and prevent the disease (Strategy and Policy)” from spreading. According to a study by Smallman-Raynor and Cliff (2008), fatality rates for H5N1 are greater than 50% in observed cases, which is much higher than the common flu virus. The virus has spread to over fifty countries on three continents, being labeled as a panzootic disease (animal disease equivalent to a pandemic in humans).
H5N1 first crossed species barriers to humans in 1997 and has extended its host range to several other mammals, causing severe disease and death. An approach to control the spread of this disease amongst birds has been culling of exposed birds, quarantine and disinfecting. However, Avian Influenza continues to spread due in part to migratory birds becoming infected (Smallman-Raynor & Cliff, 2008). The virus’s ability to evolve poses as threat and is currently classified by WHO at Phase 3 of the global pandemic alert for influenza.