vanstreels: it's definitely very distressing. i can say we've worked with these animals for many years. so we've known these populations, we've seen these colonies. and on the one hand, we are prepared because we expected it on the other. -- expected it on the other, nothing can prepare you for it . william: earlier this year, researchers confirmed that bird flu had spread all the way to antarctica, primarily affecting birds known as skuas, but so far, antarctica's iconic penguins haven't been affected . dr. vanstreels: but this virus can mutate quite quickly, right as it did when it started infecting mammals, so it could mutate again and start infecting penguins. so we're not quite out of the woods yet. william: and it's that possibility of mutation, where the virus adapts and becomes better suited to spreading from mammal to mammal, that has many on edge. particularly now that h5n1 was discovered spreading in all those dairy cows. while experts stress it's still very unlikely that this outbreak will lead to the next human pande