A CDC study found that 3 out of 150 veterinarians tested for H5N1 antibodies had silent bird flu infections. This suggests the virus may spread undetected and mutate into a more dangerous strain, raising concerns among public health officials. A CDC study found that 3 out of 150 veterinarians tested for H5N1 antibodies had silent bird flu infections. This suggests the virus may spread undetected and mutate into a more dangerous strain, raising concerns among public health officials. Health and Fitness, Health Tips, Exercises & Workout Tips, Diet & Wellness | Times of India Lifestyle