HARI SREENIVASAN: As we reported yesterday, the nation's largest egg-producing state, Iowa, has declared a state of emergency following a major outbreak of the avian flu.

Millions of chickens and turkeys there and in Wisconsin and Minnesota have been killed to try to contain the disease.

For more about all this, we are joined now via Skype from Ames, Iowa, by Amy Mayer. She is reporter for Harvest Public Media at Iowa Public Radio.

So, first of all, put this in perspective for us. How bad is it? How did it get this bad?

AMY MAYER, Harvest Public Media: We think, at this time approximately 25 percent of the laying hens in Iowa have been infected, and significant numbers of the turkeys in Iowa as well.

As you mentioned, Iowa is the largest producing state. It is the number one state for eggs. So this is a significant hit in eggs in Iowa. But, in terms of the overall marketplace, it is not a number that is going to, for example, have an impact on availability of eggs at the store.

How it got so big is really something scientists are still struggling with. They thought they had a pretty decent understanding of how this virus could spread, but the way it is moving right now has really caused them to rethink some of those ideas they had.

HARI SREENIVASAN: So, if you have got 25 percent of your chickens affected, do you have to kill off the other 75 percent? Is the whole sort of flock in danger?

AMY MAYER: I don't think anyone would say yet that the whole statewide flock is in danger.

When one farm is infected, all of the animals on that — at that site do have to be euthanized, if the virus doesn't kill them first.

And then they monitor daily every other poultry operation and backyard flock and any domesticated birds living outdoors in a 10-kilometer radius around that infected farm.

Right now, the confirmed infections in Iowa are concentrated in the northwest part of the state, with just one county in Central Iowa waiting for confirmation of infection.

So, that does still leave a significant part of the state that hasn't yet had infection.

But, again, they have to monitor very effectively within those 10-kilometer quarantine areas.

HARI SREENIVASAN: Now, there is currently no threat to humans, but are people concerned, in the disposal of these chickens or these turkeys or these birds, how do we get rid of them, and how do we get rid of them in a safe way?

AMY MAYER: That is a big concern.

As you mentioned, the concern is not right now that there would be a problem with human health, but there are environmental concerns that need to be considered.

There's four basic ways that our Department of Natural Resources has determined the birds can be disposed of. The first would be to compost on site, usually within the enclosure.

The second is on-site burial. The third would be incineration. That might involve bringing a kiln to the property to incinerate the birds. And the fourth would be taking them to a landfill.

With each of those, there are concerns. For example, with burial, you have to be mindful of the water table and how deep you are going to bury the birds to prevent water pollution.

With incineration, obviously, there need to be properly air handlers to prevent any sort of air pollution.

And, for example, landfills would mean moving the birds. And there is still concern that, even from a dead bird, the live virus might possibly be able to be moved, because they really haven't identified exactly what the transmission processes are.

HARI SREENIVASAN: Amy Mayer, a reporter for Harvest Public Media at Iowa Public Radio, thanks so much.

AMY MAYER: Thank you.