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Bird Flu

MEDICAL ENCYCLOPEDIA 
Bird Flu
Bird Flu
Causes and Risk Factors
Symptoms
Diagnosis
Treatment

Bird flu
The first reported case of a bird flu virus infecting a person directly was in Hong Kong in 1997. Since then, the bird flu virus has spread to birds in countries that include Asia, Africa and Europe. In these countries, the mortality (death) rate for humans that contracted bird flu has been greater than 60%. This flu can pose health risks to people. But what is avian flu? And how is the flu passed to humans?

What is bird flu?
Bird flu (also commonly referred to as "avian flu") gained wide spread notoriety during the first part of this decade. Avian influenza (also known as H5N1) is usually a viral infection of wild birds, most often found in migratory waterfowl. This illness is caused by a group of viruses known as type A influenzas found in wild birds.

Avian influenza is caused by this collection of different viruses rather than by a single virus type. The virus subtypes are identified and classified on the basis of two broad types of antigens. These antigens are hemagglutinin (H) and neuraminidase (N). To date, 16 H and 9 N antigens have been identified among all of the known type A influenzas. However, this virus can mutate rapidly in nature by mixing its genetic components to form slightly different virus subtypes.

Bird flu transmission

Bird to bird transmission - The route of transmission for the virus in wild birds is usually the fecal-oral route.  Influenza virus is usually shredded in the saliva, nasal secretions and feces or bird carrying the virus. Susceptible birds usually become infected when they have contact with contaminated secretions or excretions that are contaminated with secretions or excretions from infected birds.

Bird to human transmission - Bird flu can make people very sick; it can even cause death. During an outbreak of bird flu, people who have contact with infected birds can become ill. It is also possible to catch bird flu by eating poultry that is not well cooked. Another mode of human transmission is for a person to have contact with a person who has it.  Direct bird-to-human transmission occurs in this manner:

1.    Wild, infected birds shed the virus. Infected migratory waterfowl, the natural carriers of bird flu viruses, shed the virus in their droppings, saliva and nasal secretions.

2.    The virus then spreads to domesticated birds. Domestic poultry become infected from contact with these birds. Domesticated birds become infected via contaminated water, feed or soil. Bird flu spreads quickly within a domestic flock. It is inadvertently transported from farm to farm on equipment, cages, and workers' shoes and clothing. Although heat destroys the virus, it can survive for extended periods in cool temperatures.

3.    Markets provide access routes for contact for humans. Open-air markets, where eggs and birds are sold in crowded and unsanitary conditions, are primary sites for infection. This route also allows for the infection and disease to be spread into the wider community.  Humans may pick up the virus through close contact with sick birds or contaminated surfaces. A sick bird can shed the virus in its feathers.  Some people have contracted bird flu simply by touching an infected bird.

The emergence of a new viral strain that spreads easily from person to person is created when, the reassortment of genetic material human and bird flu viruses combine. This produces an entirely new subtype with a majority of human genes. This makes the virus highly contagious and, with little natural immunity among the world population, especially lethal.

Now that we understand a little more about how bird flu is transmitted to humans...who is at risk of contracting the virus? Read on for more information about the bird flu pandemic and learn how to avoid the risks of bird flu here.

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