What is the difference between H5N1 and Bird Flu?

Bird flu is a general term for some strains of influenza (flu) that are

that are found in poultry and other birds. It is more properly called Avian Influenza. There are two strains of this kind of influenza virus are known to infect humans in very rare circumstances. H5N1 is one of the specific strains of bird flu that infects humans. H7N9 is the other and new strain just discovered in humans in Spring 2013.

Flu viruses are a group of RNA viruses categorized to the three main types of influenzaviruses found in humans and other animals. These are classified as Influenza Types A, B, and C. "Bird flu" refers to an illness caused by any of the many different strains of Type A flu viruses that are endemic in birds.

All known bird (or avian) flu viruses are Influenza A viruses. Inf

luenza A viruses have been isolated from many species, including humans, pigs, horses, marine mammals, and a wide range of domestic birds but because wildfowl and shorebirds are thought to form the main influenza virus reservoir in nature, infections resulting from Influenza A viruses are sometimes termed "bird flu."

The Influenza A virus genome consists of negative-stranded RNA, which codes for 11 proteins. These viruses are classified on the basis of two of these proteins which are expressed on the surface of the virion (virus particles); these are the hemagglutinn (HA) and neuraminidase (NA) glycoproteins.

Sixteen different HA and 9 NA subtypes have been isolated from viruses in wild birds and poultry throughout the world. These can be found in numerous protein combinations (for example: H2N2, H16N3, H5N1, H7N9). Mature HA proteins mediate binding of the virus particles to host cells.

Influenza viruses of subtypes H5 and H7 are highly pathogenic and contagious in birds and can cause outbreaks of bird flu in wild fowl and poultry. People have been known to contract H5N1 bird flu by contamination through bird handling and roughly 50% of those have died. It does not usually transmit from human to human. Since 2003 360 people have died worldwide of H5N1 bird flu and tens of millions of birds have died.

H5N1 is but one subtype of "bird flu" which happens to be especially contagious and pathogenic. It is rare in humans.

At Easter time in 2013, another and more rare strain (H7N9) was found to be the organism that caused two deaths in Shanghai, China. These are the first two known human infections and deaths by avian flu viruses other than H5N1. A third victim is critically ill, also in China. None gave the flu to the others and no close contacts of any of the three have been infected. Studies are rapidly getting underway to learn more about the new strain.