>> WELCOME BACK TO NEWS LIVE. FIRST, CONCERNS ARE GROWING OVER THE POSSIBLE SPREAD OF BIRD FLU IN THE U.S. VIRUS. HAS HEALTH OFFICIALS KEEPING CLOSE WATCH ON HOW MUCH AND FAST IT'S SPREADING. AND ALSO, IF THERE IS A GROWING RISK TO HUMANS. TREVOR AULT HAS THE DETAILS. HI, TREVOR. HEY, THERE. SO THERE'S BEEN A LOT OF DISCUSSION ABOUT THE THEORETICAL RISK OF A HUMAN OUTBREAK OF BIRD FLU, INCLUDING FROM A FORMER CDC DIRECTOR. >> BUT RIGHT NOW THE CDC SAYS THE RISK TO THE PUBLIC IS LOW. >> SO HERE'S WHAT WE KNOW NOW. THE MOST IMMEDIATE THREAT THAT THIS VIRUS POSES, NATURALLY BIRD FLU, IT'S TO BIRDS. NEARLY 100 MILLION POULTRY HAVE BEEN AFFECTED ACROSS THE COUNTRY. BUT THIS IS ALSO IMPACTING COWS. THERE'S BEEN 101 DAIRY HERDS AFFECTED IN 12 DIFFERENT STATES. MICHIGAN, IOWA, THE HOT SPOTS RIGHT NOW. >> BUT THERE ARE CONCERNS THAT NUMBER COULD BE FAR HIGHER. THE DEPARTMENT OF AGRICULTURE REPORTS ZERO FARMS HAVE ENROLLED IN VOLUNTARY ON SITE TESTING. WHAT DOES THIS ALL MEAN FOR PEOPLE, THOUGH? WELL, SO FAR THIS YEAR, SOME AMERICANS HAVE BEEN INFECTED WITH BIRD FLU. BUT YOU CAN COUNT THE NUMBER OF POSITIVE CASES ON ONE HAND. THREE FARM WORKERS WHO LIKELY GOT IT FROM, THE CATTLE THAT THEY WORKED WITH. NOW, ALL OF THEM HAD MILD SYMPTOMS AND RECOVERED AND THEY DIDN'T APPEAR TO SPREAD THE VIRUS TO OTHER PEOPLE. THAT'S VERY GOOD NEWS. IT'S ONE REASON WHY THE CDC SAYS THE CURRENT RISK TO THE PUBLIC IS LOW AT THIS TIME. THERE IS NO EVIDENCE BIRD FLU IS SPREADING PERSON TO PERSON. BUT AS WE KNOW, VIRUSES DO MUTATE AND EVOLVE. THAT IS WHY EXPERTS STRESS WE