The Centers for Disease Control today briefed local public health agencies on the spreading bird flu virus.  H5N1, as this strain is known, has already been responsible for infecting one farm worker in Texas ... where the virus is thought to have jumped from a dairy cow to a human.

And today farms in Texas started the grim process of culling millions of chickens to slow the spread of bird flu.

Dr. Marcus Plescia  is chief medical officer of the Association of State and Territorial Health Officials ... he tells us they're approaching the bird flu with guarded confidence.

Dr. Plescia says they're trying to balance a message of caution ... without freaking people out.

He says that the people should be most on guard for a bird flu infection are those working in the agriculture industry or anyone who routinely comes into contact with wild bird populations.