The H5N1 virus known as Avian flu or the bird flu is undergoing what experts are calling a troubling pattern of mutations which are allowing the virus to spread from human to human.

South Korea has confirmed their fourth outbreak of this virus, this year, according to Kim Chang-sup, an official for South Korea's Agriculture Ministry.

This latest outbreak has resulted in the preventive slaughter of approximately 470,000 chickens and ducks farmed within a roughly 2-mile radius from a farm in Yeoungam which is about 236 miles southwest of Seoul.

This brings the slaughter of the number of birds to an estimated 1.3 million so far this year.

It was reported on April 8, 2008, by HSToday, that the Bird flu strains are "undergoing rapid and troubling mutations".
Dr. Michael Osterholm, director of the Center for Infectious Disease Research and Policy (CIDRAP) and the National Institutes of Health-supported Center of Excellence for Influenza Research and Surveillance within CIDRAP, had early told HSToday.us that the dramatic spread of "active" virus strains in birds around the planet has become a veritable biological soup for mutations, including a mutation which allows the virus to more easily live in a person's upper respiratory system, like in the case of the father and son in China.

As HSToday.us and HSToday have reported, current testing shows bird flu strains are undergoing rapid and troubling mutations that are pushing the viruses closer to being able to be passed between humans.
Chinese Health officials have mark the fourth confirmed instance where there was a inter-family H5N1 spread of the virus.

Today we also see that Japan has confirmed a third outbreak in the country this year, the Agriculture Ministry said in a statement.

The virus is also spreading faster than expected and surprising experts. South Korean virologists and other authorities are saying that they are witnessing a different pattern than has been seen in previous outbreaks.

The virus was first confirmed in Gimje on April 2, 2008 and within two weeks it was confirmed on six other nearby farms in the South Jeolla area.
On Monday, several suspected bird flu cases were reported at Iksan and Hampyeong, North of Jeolla Province. Authorities had confirmed 20 cases of bird flu as of Monday.

Officials from the Ministry of Food, Agriculture, Forestry and Fisheries said the virus in circulation is substantively different from previous patterns in 2002-2003 and 2006-2007.
A professor at the Korea University Medical Center was cited as saying that the virus "could easily turn into pandemic influenza", which has been a concern regarding the Avian flu since the first cases were reported.

Countless millions of birds, chickens and ducks have been slaughter to try to prevent the spread of this virus, but with the new patterns emerging of mutating strains, those preventative measures may not be effective for long into the future.

If the virus mutates to the point where more cases of human to human spread is seen, then prevention will be far harder to accomplish logistically.

You can find out more about the Influenza A (H5N1) virus - also called "H5N1 virus", (bird flu) at the CDC, here and here.

You can also find out more about recent outbreaks, studies and further studies into the virus at the World Health Organization (WHO).

Who has also launched the Influenza Virus Tracking System which can be accessed by the public here.