The following is a rush transcript of the May 3, 2009, edition of "FOX News Sunday With Chris Wallace." This copy may not be in its final form and may be updated.

CHRIS WALLACE, HOST: Where do we stand with swine flu? Joining us now, the top three officials charged with protecting our country: Secretary of Homeland Security Janet Napolitano, Secretary of Health and Human Services Kathleen Sebelius, and Dr. Richard Besser, acting director of the Centers for Disease Control.

And welcome to all of you.

Dr. Besser, give us an update. What's the latest on the swine flu, on the spread and the severity of the disease?

DR. RICHARD BESSER, ACTING DIRECTOR OF CDC: Thanks, Chris. You know, as we've been saying for days, this is a rapidly evolving situation. There's a lot of uncertainty. Each day we're learning tremendous amounts of information.

What we're seeing here in the United States — we have 160 confirmed cases in 21 states. And as we say those numbers, they're immediately wrong, because there's work going on in every state to look for more cases.

We're hearing from unaffected states, or previously undiagnosed states, this they're seeing cases. The World Health Organization has reported this morning 15 countries with confirmed cases.

WALLACE: We have learned in the last couple of days more about the virus, and we are learning that it lacks some of the properties that made earlier flus so lethal.

We also are learning that perhaps the lethality of the Mexican strain may have been overstated. Does that mean we're out of the woods?

BESSER: It does not. It's encouraging information. You know, when we get a new strain of flu, we'll look for what are called known virulence factors. These are things that in the past have been associated with severe disease.

And as we've looked for those, we haven't seen the known ones associated with H1N1, and we don't see the one that was associated with 1918. But every strain is new, and so there could be factors that we're unaware of that we would need to look for in this strain.

WALLACE: So we're not out of the woods.

BESSER: We're not out of the woods. The information that we've been getting over the past couple days is encouraging.

WALLACE: Secretary Sebelius, Vice President Biden stirred up quite a storm this week when he told the advice that he said that he had given to his family. Let's watch.

(BEGIN VIDEO CLIP)

VICE PRESIDENT JOE BIDEN: I would tell members of my family, and I have, I wouldn't go anywhere in confined places now. It's not that it's going to Mexico. It's your in a confined aircraft. When one person sneezes, it goes all the way through the aircraft. That's me.

I would not be at this point, if I — it they had another way of transportation, suggesting they ride the subway.

(END VIDEO CLIP)

WALLACE: Secretary Sebelius, is any of that true?

SECRETARY KATHLEEN SEBELIUS: Well, I think, Chris, what's important is that a travel advisory has been issued for American travelers who are voluntarily going to Mexico, not mandatory trips, but pleasure trips. And we've asked people to discourage travelers from taking those trips right now until we know more, as Dr. Besser said. I think that other kinds of travel — if you're sick, it's a good idea not to expose others to that sickness. But certainly, airplane travel, train travel — my whole family's been here this weekend. My elderly father and aunt will be on a plane this morning. My son and his fiancee will be on a train back to Boston. I'm flying to Atlanta on Monday.

So traveling and being in closed places is certainly something we encourage people to continue to do.

WALLACE: So I mean, I have to tell you, some people have said to me since Vice President Biden talked, maybe you guys are telling the public one thing, but at the highest levels of government you've heard something else, and that — no, you're saying to me that everything that Vice President Biden said about — I'm not talking about travel to Mexico — being in a confined space, being in a classroom, being in a school, being in a subway — no health danger to any of that?

SEBELIUS: Well, what — again, with — we're letting the science lead this investigation and trying to be prudent about situations.

We've asked schools to close if there is a confirmed case, because what we're seeing in New York and other areas is this is transmitted very easily. Children are great carriers of viruses — and to separate those children until we know more about this situation.

So there is some specific health advisory, but it certainly is not don't get on a plane, don't get on a train, don't get on a subway. And as I say, in my own family, we've got lots of travelers today and we're continuing to do that.

WALLACE: So why would the vice president tell his family that? Are we to believe that the vice president of the United States is a crackpot?

SEBELIUS: I think that each member of our country makes decisions about themselves and their family and about safety and security. What we're telling you is what the science says.

WALLACE: Secretary Napolitano, you testified before Congress this week, and I want to explore the difference between what you're telling the public and what some very smart people, like Senators McCain and Lieberman, asked you.

First question: Why not close the border with Mexico?

SECRETARY JANET NAPOLITANO: Well, again, we take our lead from science, from the epidemiologists, because we want to lean into this. We want to do the right thing. But we don't want to react in a way that's not going to actually help contain the spread of the flu.

And what the scientists tell us unanimously is that closing the border in this circumstance doesn't make any sense, because this flu already has spread. It's in a number of countries now. And I think you also have to understand the inordinate cost associated with closing a border, the number of jobs associated with that, the trade that goes back and forth.

If it had a benefit to it, you would — you would make that calculation perhaps a little differently, but when the scientists are uniform in saying that's not going to help you contain the flu, we're going to focus our efforts on what we can do to contain the flu...

WALLACE: But — but...

NAPOLITANO: ... and that's on mitigation here.

WALLACE: ... but Secretary — and again, this is a question a lot of people have been asking me — isn't that like saying if you have one mosquito in your house that's carrying a disease, you shouldn't close the door, because there's one mosquito there and, you know, why close the door and get — and keep any other mosquitoes out?

Aren't you better off with fewer mosquitoes carrying disease?

NAPOLITANO: This isn't about mosquitoes. This is about the flu, and the way that...

WALLACE: Well, I understand. But we're talking about people who are carrying the flu.

NAPOLITANO: Exactly. But the way the flu is transmitted — and I'll let Dr. Besser take this on as well, because we've answered this question a lot this week, and we've thought about it a lot.

But again, the flu is here. It's a virus. The way it is transmitted, closing the border in and of itself is not going to help or slow how it's going to spread around our country.

What will help — what will help is — are the containment strategies. So if you're sick, don't go into a contained place. By the way, the vice president did take the train home from work yesterday, so I think that, you know, he himself would say if you're sick, don't get into a contained place. If you have a child who's sick, don't send the child to school.

Those are the strategies that will ultimately help us contain the virus.

WALLACE: Why isn't — Secretary Napolitano, why isn't the U.S. taking some of the same precautions that other countries are, like setting up thermal cameras at checkpoints to check for travelers who may have fevers?

Other countries are canceling all flights between them and Mexico and back.

NAPOLITANO: Well, again, because we think we're making the right judgments for the safety of the American people. If we thought that would actually help, we would do it. But the advice is it — not only will it not help, but again, it will divert efforts and costs and everything else away from things that will help, and that's what we're focused on.

WALLACE: Dr. Besser, because we're getting kind of a mixed message here, are we overreacting to this outbreak? Are the government and the media guilty of hyping this?

BESSER: We are not overreacting to this outbreak. With a new infectious disease, there's a lot of unknown, a lot of uncertainty. And you basically get one shot. You get one chance to try and reduce the impact on people's health.

And so what you do is you take a very aggressive approach. And as you learn more information, you can tailor your response.

I would like to address the border issue, because I think that there's a lot of misunderstanding about that. As we planned for an outbreak or a pandemic of flu around bird flu, the idea that if this started on distant shores, increasing screening at the border might give us, at best, a couple weeks to do some of the things that you need to do to prepare.

Once it's entered your borders, flu is a very easily transmittable virus. And in fact, some people have no symptoms at the time that they're able to transmit. And so the efforts at a border at that point are really not going to help you in your outbreak and could be directed much better in ways that will improve the health of your communities.

WALLACE: I want to talk about the question of overreaction, though, Doctor. The city of Fort Worth shut down its entire school system — 147 schools, 80,000 students — because one kid had a confirmed case of swine flu. Is that an overreaction?

BESSER: You know, what you'll see with any outbreak, and in a setting of uncertainty, is guidance that comes down, but you're going to see application of that in different ways in different places.

And what we'll learn from that moving forward is what were the most effective measures in this — for this particular virus in this country. And as we go forward, that will help guide what things we recommend people do in the future.

WALLACE: Well, that's a bureaucratic answer — doesn't answer my question. Is it an overreaction? Is there any sensible public health reason to shut down 147 schools when one kid in one school has the swine flu?

BESSER: If it turned out — and thankfully that's not the case. If it turned out that this virus had some of those factors we were talking about, I think we would be looking at that school district and saying, "Wow, weren't they proactive? They were forward-thinking. That was a great thing to do."

As we learn these things about the virus, transmission in communities and severity, we'll be able to say whether that was necessary or whether that was more than would be required to control it in their community.

WALLACE: But I think, Secretary Sebelius, one of the things that confuses people is that there seems to be an apparent disconnect here.

For example, while all of you talk about the possible, the potential, danger here, as I understand it, the government has no plans to develop a swine flu vaccine until — until you finish the completion of the vaccine for next fall's regular swine — regular seasonal outbreak.

Why — which is more of a threat, the swine flu now or next season's regular seasonal outbreak?

SEBELIUS: Well, first of all, Chris, I think both are going on simultaneously. The scientists have identified a strain, a virus strain, that's being tested and grown as we speak.

What hasn't been determined yet — and it will be determined by the scientists — is whether or not vaccine production for H1N1 makes sense, whether we really do want to do full-scale production.

What we know is seasonal flu, year in and year out, affects millions of Americans. About 200,000 people end up in the hospital and 36,000 people die. That's what happens every year with seasonal flu.

So production of that vaccine is critical to making sure that we don't have increased deaths associated with seasonal flu.

And one of the things that we know is that even if this current situation seems to be lessening, if we are cautiously optimistic, we really don't know what's going to happen when real flu season hits with H1N1 virus.

So aggressive activity is going to continue, the testing and production, oversight of the FDA, and we are going to be ready to go with a vaccine. It makes it even more important with a new flu strain that we do both simultaneously.

WALLACE: But you aren't doing both simultaneously. You're manufacturing the regular flu. You're not manufacturing the swine flu.

SEBELIUS: Well, Chris, it's too early to manufacture anything. What they need to do right now with this H1N1 virus is to test it, is to make sure they've got the right antidote to this particular viral strain, to make sure we have the right dosage, and then make a decision based on the science of what we know whether or not full- scale vaccine production — you can't make a vaccine unless you know what's in the virus and what's going to...

WALLACE: Did you say — and I don't want to misquote you. Did you say you're cautiously optimistic on the swine flu?

SEBELIUS: Well, what Dr. Besser and I — again, I'd like to pivot back to the scientists. What I think is being determined is that the lethality, which initially presented itself as part of the Mexican situation — the deaths of a real - - an age group that you don't typically see in flu season — is not seeming to present itself.

But, Dr. Besser, maybe you can clarify where...

BESSER: I mean, we're seeing encouraging signs and — you know, I want to put that in perspective, though. As the secretary was saying, the seasonal flu, something that hits us every year — we see 36,000 deaths.

Here, we're seeing encouraging signs that this virus so far is not looking more severe than a strain that we would see during seasonal flu. And so I still expect that this will have significant impact on people's health, but so far the signs are that it is not more severe than what we've seen in a seasonal flu.

WALLACE: Secretary Napolitano, a lightning round — quick questions, quick answers on practical questions. A Harvard School of Public Health study found that 25 percent of people said they're staying out of malls. Sensible or not necessary?

NAPOLITANO: Well, if you're sick or you feel sick, stay out of the mall.

WALLACE: No, no. I'm talking about healthy people.

NAPOLITANO: No. I mean, you should consider your normal daily activities, unless you're sick or have someone in your household who is sick. Then you should contain yourself.

WALLACE: Eight percent of people say they're wearing masks.

NAPOLITANO: Again — again — depends on the individual circumstance, if you have a particular illness underlying that. But again, common sense — you don't need to wear a mask.

WALLACE: And if you're healthy, is there anything in terms of your normal daily living that you shouldn't be doing?

NAPOLITANO: Well, what you should be doing is covering your mouth when you cough. What you should be doing is washing your hands regularly and thoroughly.

What you should be doing is being very situationally aware, meaning if you or anybody in your household appears to be coming down with the flu, stay home. Don't go to the mall. Don't go to other places where you could infect somebody else.

WALLACE: And finally, Secretary Napolitano, as the former — we have to pivot here — as the former attorney general of Arizona, your name has been put on the, quote, list as a possible replacement for David Souter on the Supreme Court. Any interest in that job, if offered?

NAPOLITANO: You know, Chris, I've got to tell you, I've got my hands full with the flu right now, and I'm just going to stick with that.

WALLACE: Well, that's a — that's a non-answer.

NAPOLITANO: That's all you're going to get.

WALLACE: You wouldn't accept the job of Supreme Court justice?

NAPOLITANO: Listen, I think the president has many, many excellent choices before him, and that's his choice to make.

WALLACE: Secretary Napolitano, Secretary Sebelius, Dr. Besser, we want to thank you all for coming in and answering a lot of questions that I know are on people's minds. Thank you.

SEBELIUS: Thank you, Chris.

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