Currently, all evidence points to domestic ducks as the ones who can shed it and transmit it and not get sick.

It's an easy thing to do and if we don't get it under control in poultry, every year it's going to get back in wild birds and every year it's going to spread around again and we'll never get this thing under control.

We start at a market somewhere in Guangdong Province in China. And it's packed with cages, and you'll have chickens, and you'll have ducks. You might have some other animals -- cats, dogs, turtles, snakes -- and they're all stacked in cages, and they're all spreading their germs to each other.

It's a race against this virus. And the clock is ticking. The challenge now is can we make enough vaccine to protect the world?

We should concentrate on the outbreak in birds. Go upstream and contain it at the source.

If it changes to be able to go easily from human to human, it will have disastrous consequences if we're not prepared.