There are many different subtypes of type A influenza viruses. These subtypes differ because of changes in certain proteins on the surface of the influenza A virus (hemagglutinin [HA] and neuraminidase [NA] proteins). There are 16 known HA subtypes and 9 known NA subtypes of influenza A viruses. Many different combinations of HA and NA proteins are possible. Each combination represents a different subtype. All known subtypes of influenza A viruses can be found in birds. Usually, "avian influenza virus" refers to influenza A viruses found chiefly in birds, but infections with these viruses can occur in humans. The risk from avian influenza is generally low to most people, because the viruses do not usually infect humans. However, confirmed cases of human infection from several subtypes of avian influenza infection have been reported since 1997. Most cases of avian influenza infection in humans have resulted from contact with infected poultry (e.g., domesticated chicken, ducks, and turkeys) or surfaces contaminated with secretion/excretions from infected birds. The spread of avian influenza viruses from one ill person to another has been reported very rarely, and transmission has not been observed to continue beyond one person. "Human influenza virus" usually refers to those subtypes that spread widely among humans. There are only three known A subtypes of influenza viruses (H1N1, H1N2, and H3N2) currently circulating among humans. It is likely that some genetic parts of current human influenza A viruses came from birds originally. Influenza A viruses are constantly changing, and they might adapt over time to infect and spread among humans.
Symptoms of avian influenza in humans have ranged from typical human influenza-like symptoms (e.g., fever, cough, sore throat, and muscle aches) to eye infections, pneumonia, severe respiratory diseases (such as acute respiratory distress), and other severe and life-threatening complications. The symptoms of avian influenza may depend on which virus caused the infection.
Those who have become infected have had close direct contact with infected birds. Historically, human infection with avian influenza viruses has usually caused mild conditions such as conjunctivitis (eye infection) and mild flu-like symptoms. More severe infections can lead to pneumonia, acute respiratory distress, viral pneumonia, and other severe and life-threatening complications.
Because these viruses do not commonly infect humans, there is little or no immune protection against them in the human population. If H5N1 virus were to gain the capacity to spread easily from person to person, an influenza pandemic (worldwide outbreak of disease) could begin.
So H5N1 is able to infect people because it is able to cross the species-barrier, although it does not do this easily. In human populations, where domestic pigs and wild and domestic birds live in close proximity with people, the mingling and exchange of human and animal viruses can more easily occur.
There are several types of avian influenza. The strains that cause the greatest number of deaths are called highly pathogenic avian influenza (HPAI). The HPAI strain involved in the current outbreak is called H5N1. It was first recognized in 1997 in Hong Kong, where it caused poultry outbreaks and led to infections in 18 people with 6 deaths. Fortunately, the outbreak was halted in Hong Kong at that time by strict control measures in the poultry industry.
H5N1 flu refers to the transmission and infection of H5N1. H5N1 flu is a concern due to the global spread of H5N1 that constitutes a pandemic threat.
FINAL THOUGHTS Most Experts Agree That The Bird Flu Pandemic? Is IMMINENT!
What do You do When the Doctors, Nurses, and Carers Begin Dying?
Do The Recent Bird Flu Stories Scare You? ... They Should!
Experts put the probability of a global influenza pandemic at 100% - an absolute certainty!
When it hits it's estimated that it will last 12-18 months, will touch every corner of the globe and according to The Director of the Center for Infectious Disease will kill anywhere between 30 Million and 380 Million People!
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