CDC Telebriefing Transcript

Back to School: CDC Encourages Communities to Create Safer Routes to School; and West Nile Virus Activity Update

August 15, 2002

MS. HAYES: Good morning. Hi, I'm Gail Hayes, senior press officer at CDC, and I'd like to welcome the reporters that have joined us today.

We've got three speakers. First will be Dr. Catherine Staunton, and that's spelled C-a-t-h-e-r-i-n-e, and her last name, S-t-a-u-n-t-o-n. She's one of CDC's unintentional injury expert. She'll provide brief remarks about the barriers for children walking or biking to school.

Then Ms. Jessica Shisler--and that is spelled S-h-i-s-l-e-r--one of CDC's health educators, will talk about school transportation modes in Georgia, and following their presentations we'll take your questions.

Then Dr. Lyle Petersen--and that's P-e-t-e-r-s-e-n--one of CDC's infectious disease experts, will provide an update on West Nile virus activity in the United States.

Let's get started with Dr. Staunton.

DR. STAUNTON: Good afternoon. I'm Dr. Catherine Staunton with the CDC's Center for Injury Prevention and Control. Physical activity is an important part of a healthy lifestyle, yet parents in the U.S. report that only about one child in seven starts the day by walking or biking to school. About half of children are transported to school by private vehicle and a third by school bus. Understanding why more parents don't encourage their children to walk and bike to school is important for addressing this public health concern.

Until now, there has been no nationwide data addressing this question. Today's MMWR reports on the first nationwide study to help us better understand the concerns that parents have about letting their children walk and bike to school. This study finds the two main reasons that parents don't encourage these healthy behaviors are because of long distances and traffic danger. Parent are justified in their concerns. Other studies have shown the average distance to school is long--two miles. However, even children living within walking and biking distance usually do not walk or bike to school.

Among U.S. children living within one mile of school, only one in three trips to school are made by walking or biking. Also, walking and biking can be dangerous forms of transportation. Pedestrian bicycle injuries are a leading cause of death among U.S. children.

Our study found when parents were asked what made it difficult for their children to walk and bike to school, they reported the following factors: long distance, 55 percent; traffic danger, 40 percent; weather, 24 percent; danger of crime, 18 percent; school policy, 7 percent; and other reasons, 26 percent.

Only 16 percent of parents reported no barriers to walking or biking to school. Among the children with no reported barriers, 64 percent of children did walk and 21 percent of children did bike to and from school at least once a week. Children with no reported barriers were six times more likely to walk or bike to school than children with one or more reported barriers.

According to parents, both primary school-aged children and secondary school-aged children were equally likely to walk or bike to school. However, parents are more concerned about the risk of traffic and crime danger in the younger children.

In summary, most children face substantial barriers to walking or biking to school. However, when these barriers are not present, the majority of children do walk or bike to school.

CDC approaches this public health concern by recommending that community leaders and parents work together to address these barriers. For example, walking and biking are safer if motor vehicle speed and traffic decreases and if drivers' visibility of pedestrians increases. Programs that encourage adult supervision, such as the walking school bus, also improve safety. Another suggestion is to consider building new schools closer to homes to decrease distances. These multi-pronged efforts provide healthy transportation alternatives for children and produce neighborhoods that ensure safer walking and biking for all ages.

Thank you.

MS. HAYES: I'd like to turn it over now to Ms. Shisler to talk about her findings.

MS. SHISLER: Hello. I'm Jessica Shisler, a health education specialist in the Division of Nutrition and Physical Activity at the CDC.

Georgia is the first state to collect statewide data on the number of children who walk to school. These data were collected by the Georgia Department of Human Resources, Division of Public Health, by adding two questions on modes of transportation to school to the Georgia (?) survey that was conducted May to August of 2000. This study found that only 4.2 percent of Georgia's school-aged children walked to school on majority days of the week. Of those who live within one mile of school, fewer than one in five children walk to school.

Older children are more likely to walk than younger children, and non-Hispanic black children are more likely to walk than other races and ethnic groups.

Why is walking and bicycling to school important? Well, studies show that even moderate physical activity, including walking, at least 30 minutes on all or most days of the week offers substantial health benefits. At a time when sedentary activities, such as watching TV, playing video games, and using a computer, compete for children's free time, we need ways to build physical activity into children's daily routine.

Walking and bicycling to school offer an ideal opportunity for children to fulfill part of the recommended daily physical activity.

National statistics show that trips made by walking have steadily decreased while trips made by automobile have increased. Interestingly, over this same time period, levels of obesity and overweight among children and adults have climbed. Over the past 30 years, the percent of overweight children has more than doubled. In Georgia, obesity in adults has more than doubled over just the last decade, not surprisingly, since Georgia ranks 39th of all states in levels of physical activity.

Walking to school offers an opportunity for children to get daily physical activity. The CDC supports walking to school through the Kids Walk to School Program, developed in response to the low rates of walking to school, inadequate levels of physical activity in children, and to the alarming increase of overweight children in the U.S.

Walk-to-school programs encourage community members to work together to identify ways to overcome barriers to walking and biking to school and establish safe routes for children to walk and bike to school in groups accompanied by adults.

By adding questions to existing surveys, other states can inexpensively and reasonably collect some more data. In the fall of 2002, Georgia will add additional questions to collect data on barriers to walking and bicycling to school. These data can be used to monitor prevalence of walking and bicycling to school and identify ways to increase opportunities for walking and bicycling to school.

Thank you.

MS. HAYES: Great. We'd like to open it now for any questions for these two studies.

AT&T OPERATOR: And, ladies and gentlemen, if you wish to ask a question, please depress the 1 on your touch-tone phone. You'll hear a tone indicating you've been placed in queue and may remove yourself from the queue at any time by depressing the pound key.

If you are using a speakerphone, please pick up your handset before you press the 1.

And our first question is from the line of Christin Wyatt with the Associated Press. Please go ahead.

QUESTION: Yes, ma'am. You all said this was the first study of the barriers to children walking. Was there an earlier study just of how many children do walk or cycle to school? And can you tell me anything about a decrease in the numbers of children who walk or cycle to school?

DR. STAUNTON: This is Dr. Staunton, and I'll address that question. There is a nationwide transportation survey, the National Personal Transportation Survey, that does ask the number of children that walk and bike to school. And it's that survey that says nationwide 10 percent of children walk to school and 1 percent of children bicycle to school.

That survey has shown over--over the past decade?--decade or a little less than a decade that the number of walking trips made by children has decreased by 37 percent. I'm not sure, however, about the percentage walking specifically to school.

AT&T OPERATOR: And, Ms. Wyatt, does that conclude your question?

QUESTION: I'm sorry. I have--yeah. Sorry.

AT&T OPERATOR: Thank you, Ms. Wyatt. And our next question will be from the line of Adam Marcus with Health Scout. Please go ahead.

QUESTION: Hi. I was interrupted so I wasn't sure whether this is was answered in the previous question, but the figure in the editorial note for the Georgia study of 31 percent of students walking who live less than a mile from school in the 2010 objectives, where does that come from?

MS. SHISLER: This is Jessica Shisler. Again, that data comes from the Nationwide Personal Transportation Survey that Dr. Staunton just mentioned, and the reason--she mentioned 10 percent because that's of all school trips of any distance. And when you look at the number within a one-mile distance from school, it's 31 percent of all school trips are made by walking.

QUESTION: So the first here is a first of barriers to--perceived barriers to transportation and not necessarily of the way kids get to school?

MS. SHISLER: That is correct.

QUESTION: And is--am I still on?

MS. HAYES: Yes, you're still on.

QUESTION: Is distance really considered to be a barrier? I mean, I think--when my parents were in school, they walked five miles each way in the snow, you know, every day of the year. And in fact in order to get 20 minutes, 20 minutes a day of exercise, if you live less than a mile away, you'd need to walk more than a mile; right?

MS. : Walking to school is just one way to get the daily recommended, recommendation of physical activity. So we encourage children that live within one mile of school, who have a safe route to school, to walk to school.

QUESTION: But not after one mile? I mean, not farther than one mile?

MS. : We just encourage that children that live within one mile of school can easily walk that distance. Older children can walk further distances.

CDC MODERATOR: Are there any more questions?

AT&T MODERATOR: Yes. Mr. Marcus, does that conclude your question?

MR. MARCUS: Yes; thank you.

AT&T MODERATOR: Thank you.

We have two additional questions at this time. Next, we'll go the line of Maureen McKenna [ph] with Atlanta Journal. Please go ahead.

QUESTION: Hi. Thanks for doing this teleconference. This question goes to both the authors. Can you correlate any of the data that you found on perceived barriers to children walking or biking to school with any demographic data? For instance, I'm wondering if the perceived--the distances are in suburban communities where there aren't sidewalks, or if the kids who walk to school are in families where both parents are more likely to work and are not available to drive the kids to school? Anything like that?

DR. STAUNTON: This is Dr. Staunton, and I'll address that question first. The number of people who answered these survey questions were 611, so we did look at the data, broken down by geographic density, by income, by parents' education.

The data's not real strong just because the number is fairly low, but we did certainly find correlations. The more densely populated the area is, the more likely the child is to walk. The lower the family income is, the more likely the child is to walk as well.

MS. SHISLER: And on the Georgia study, they did not look at any variables other than urban and rural, and they show that children that live in urban areas are more likely to walk; however, it is not statistically significant.

DR. STAUNTON: That's right.

QUESTION: Okay; thanks.

AT&T MODERATOR: And our next question from the line of John Lowerman with Bloomberg. Please go ahead.

QUESTION: Hi. Thanks for taking my question. I'm wondering if there is any plans by CDC to address the speed of traffic or traffic danger as a public health problem relating to this specific issue of preventing people from getting exercise?

DR. STAUNTON: This is Dr. Staunton and I'd be glad to address that question. Speed of traffic certainly contributes to pedestrian injury, including fatal injury. Pedestrian injuries are a leading cause of death in children, and speed as well as amount of traffic, and how close children are to traffic contribute, and is a focus of the injury center at the CDC.

To help counteract this, we recommend that parents and community leaders help children choose and create safe routes to school, that parents teach children traffic safety, and be good role models for traffic safety as they walk with the children, and that children are supervised whenever they are walking or biking by an adult until they're at least ten years of age.

Bicycle helmets also are very helpful in decreasing injuries.

QUESTION: So does that mean no, that there are no additional plans to address traffic speed as an issue in preventing people from getting adequate exercise?

MS. SHISLER: The CDC's Kids Walk--

QUESTION: Is this Jessica, or is this--who's talking now?

MS. SHISLER: This is Ms. Shisler.

QUESTION: Okay.

MS. SHISLER: The CDC has developed the Kids Walk to School Program that I mentioned earlier and it includes ways for communities to work together with police to monitor and enforce speeds during the morning and afternoon commute to school.

QUESTION: Okay; thank you.

DR. STAUNTON: I'd also like to add to that question that the CDC, in collaboration with National Highway Transportation Safety Administration, has outlined guidelines for pedestrian safety that include traffic calming measures.

AT&T MODERATOR: Thank you, and we will have a follow-up question from the line of Adam Marcus [ph] with HealthScout. Please go ahead.

QUESTION: Hi. With the Kids Walk to School Program, when was that implemented and how many states or communities have taken part so far?

MS. : The Kids, the CDC Kids Walk to School Program has been around for about four years, and states across the country have been picking them up and developing programs in their communities over the past four years.

In addition, other walk-to-school initiatives were picked up and brought over from Australia, England, and Canada, and that's how the U.S. worked to do the Kids Walk to School Program--based on those programs.

QUESTION: But do you have any idea of the numbers of communities or states that have similar programs?

MS. : We know that all 50 states are participating in the International Walk To School Day event which is in October of each year, which countries across the world participate, and we know that 50 states in the country also participate.

We also have case studies on states that are doing walk to school programs, including Kids Walk to School. However, we do not know the exact number.

CDC MODERATOR: If I could, I'd like now to move on to our West Nile update from Dr. Lyle Petersen.

DR. PETERSEN: Good morning.

The CDC continues to work with state and local health departments around the country to help control West Nile virus. As of August 14th, as reported in the MMWR, there have been a total of 156 cases reported from eight states and the District of Columbia to CDC, with nine fatalities.

The breakdown of the cases and where they are occurring are in your MMWR, and I won't repeat them right now, but they're there for your reading.

In addition, 37 states, the District of Columbia and New York City are reporting West Nile activity in birds, mosquitoes, and horses.

We currently have about 20 CDC employees in Louisiana, Mississippi and Arkansas, helping local officials look for cases, trap birds, and study mosquito populations, as well as looking at the clinical aspects of the disease in humans.

In addition, CDC continues to work with state and local health departments to educate the public about steps they can take to protect themselves.

These steps would include eliminating breeding sites around a person's property and in the community, using repellent containing DEET, wearing long sleeves and pants, and trying to stay indoors at dawn and dusk when mosquitos are most active.

CDC continues to operate a hotline from 8:00 a.m. to 11:00 p.m., Eastern Standard Time, Monday through Friday, and 10:00 a.m. to 8:00 p.m. Eastern Standard Time on Saturday and Sunday, where the public can call for information on West Nile virus.

The hotline was set up early last week and has received over 3,500 calls. I'd once again like to publicize these numbers.

In English, people can call at 1-888-246-2675, and that again is 1-888-246-2675.

And in Spanish, people can call 1-888-246-2857. I'll repeat that. 1-888-246-2857. And for the hearing impaired at 1-866-874-2646. That's 1-866-874-2646.

Finally, CDC is developing public service announcements on preventing West Nile virus infection for distribution to the media through state and local health departments and we hope to distribute those as soon as possible.

Thank you.

CDC MODERATOR: Any questions now for Dr. Petersen?

AT&T MODERATOR: Ladies and gentlemen, if you wish to ask a question at this time, you may depress the one on your touchtone phone.

If your question has already been addressed and you wish to remove yourself from queue, you may press the pound key.

Also, if you are using a speaker-phone, please pick up your handset before pressing the one.

Our first question from the line of Todd Richman [ph] with Associated Press. Please go ahead.

QUESTION: Hi, Dr. Petersen.

DR. PETERSEN: Hi.

QUESTION: Hi. We had a horse that just went down, up here in Wisconsin, and preliminary tests show West Nile virus was responsible, and we're thinking how susceptible are humans to this and is this really a concern for folks in everyday life, and should they be looking for vaccinations themselves?

DR. PETERSEN: I'm a little confused by your question. Are you talking about vaccination for horses or people?

QUESTION: People.

DR. STAUNTON: Okay.

QUESTION: Should people be seeking vaccinations?

DR. PETERSEN: Yeah. Just to backtrack a bit. What we've seen in studies that we've done in the New York metropolitan area where we've done household-based sero surveys, is that pretty much the entire population is susceptible to getting infected with the West Nile virus.

QUESTION: Meaning human population?

DR. PETERSEN: Human population. And that makes sense since everybody could be bitten by a mosquito bite.

QUESTION: Uh-huh.

DR. PETERSEN: But the proportion of those who get infected, who go on to develop more severe disease is highly related to age.

QUESTION: Uh-huh.

DR. PETERSEN: The older you are, the more likely you are to develop severe West Nile disease.

QUESTION: Uh-huh.

DR. PETERSEN: What we know from the serological surveys we've conducted is that about one in five persons overall develop what we call West Nile fever, which is simply a mild febrile illness that lasts a few days, usually three to six days, and then goes away on its own without any permanent sequelae.

I describe it as kind of a mild, flu-like illness. About one in 150 persons, overall, go on to develop encephalitis or meningitis. So most people that actually get infected with the virus have no symptoms at all.

CDC MODERATOR: This is Kara Hayes the moderator. Someone's typing in the background and if I could ask you to please put your phone on mute. Thank you.

DR. PETERSEN: Now the question comes, you know, about the human vaccine. There is a vaccine that's available for horses. This is an experimental vaccine but it's available on the open market. The fact that you've got an infected horse in your area is not surprising since West Nile activity was found there last year, but it just emphasizes to horse owners that they ought to seriously consider getting their horses vaccinated.

Now as far as a human vaccine goes, there's a couple of companies that are in the process of developing a human vaccine.

But any human vaccine is a number of years off. The vaccine first has to be developed, it has to be proven to be safe in humans, and it also has to be proven to be efficacious in humans.

QUESTION: So that one does not currently exist?

DR. PETERSEN: One does not currently exist. Only a horse vaccine exists.

CDC MODERATOR: If I could ask that we also see how many other questions might be in the queue so that we give everybody an opportunity to ask a question, please.

AT&T MODERATOR: Thank you.

At this time we have nine additional questions in queue. Would you like to move on to the next question?

CDC MODERATOR: Please.

AT&T MODERATOR: Thank you.

The next question will be from the line of Seth Bornstein [ph] with Knight-Ridder. Please go ahead.

QUESTION: Yes, Dr. Petersen, thanks again for doing this. If we could step back and take a look at the broader picture of mosquito-borne illnesses in the United States, can you tell me how--you k now--does the West Nile virus, how it's gone through this year, show us anything about future vulnerability to the United States of things like Japanese bee [?] or Rift Valley or the like?

DR. PETERSEN: Right. What the experience with the West Nile virus shows is that importation of vector-borne diseases can spread at a very rapid rate, and it's quite clear that, you know, the--it's clear to us, anyway, that we expect that the virus will in fact go coast to coast, it's just a matter of time.

And it's going--and it has done so rather rapidly. So importation of exotic viruses certainly can pose--can spread widely in the--geographically. [Clarification: The experience with the West Nile virus shows that importation of vector-borne diseases can spread at a very rapid rate and spread widely. We expect the virus will in fact go coast to coast, its just a matter of time.]

What that says for other diseases like Japanese encephalitis or Rift Valley fever depends on how these diseases are normally spread and what kind of mosquitoes spread them.

With Japanese encephalitis, the most common vector species for spreading that virus are not here in the United States. And whether the virus--this virus would have any major potential to spread here in this country is unknown, but probably not.

There are--Rift Valley fever, the mosquitoes that do spread that are mosquitoes that--the native species of mosquitoes here could presumably spread that virus, and so Rift Valley fever is obviously a concern.

Other viruses such as yellow fever, dengue, and malaria--I mean, not malaria, but yellow fever and dengue actually were introduced into this country and had established themselves until mosquito control efforts managed to eliminate them. But there would be a potential for resurgence of these viruses if they were reintroduced since the vector mosquitoes still are here in parts of the country.

QUESTION: So could I just follow up on this one quick?

MS. HAYES: We've got a lot of people in the queue, and I'd like to make sure we get an opportunity to do that, and I'll give you a number to call later to follow up.

Could we please take the next question?

AT&T OPERATOR: Our next question from the line of John Cope (ph) with Times Picayune. Please go ahead.

QUESTION: Greetings from West Nile Central. I'm calling from New Orleans, and we've had, as has been pointed out, a squadron of CDC people here. I'm wondering if while they've been working with people with the disease and with health officials and with doing basic grunt epidemiological work, they have been--they have learned anything new about this illness that people I write for, who are frantic about dead birds, need to know.

DR. PETERSEN: Well, I think it's still too early to say. There are a number of findings coming out of these studies that are important. But I'd prefer not to comment on these findings until the results are fully analyzed. What I don't want to tell people is preliminary results that may not be correct.

QUESTION: Okay. If I may ask a follow-up, is the virus moving quicker or--than you expected? Because it just seemed to explode this summer after being up in the Northeast for--from 1999 to last year.

DR. PETERSEN: Yeah, that's an excellent question. If you look at the spread of the virus, in 1999 the virus was mainly detected in the New York City area. However, there was one dead crow that was found in the Baltimore area. So as early as 1999, it was pretty clear that this virus was going to spread and it was going to spread via bird.

What we didn't know is whether the virus would persist over the winter, and we all know the answer to that at this point. So once we knew the virus would persist over the winter of '99 to 2000, we realized it was just a matter of time until the virus was going to go--spread a lot fever. By 2000, the virus had spread mainly along bird migration routes into the Mid-Atlantic and New England states, and by 2000, the virus had been detected in large areas of the Eastern United States, including the Southeast.

So the--and so what--so the virus was already there last year in these places, in many of the places where the virus is now active, in Louisiana and Mississippi and Alabama.

MS. HAYES: If we could take the next question, please, and because we have a lot of people in the queue, I'd ask that you just have one question, and then I'll give you a phone number if you want to do follow-up.

DR. PETERSEN: Okay. Let me just finish this question. So once the virus was already established in those areas, it was--it was--and it's not surprising that there's been much more activity this year because the virus was already there for a year.

MS. HAYES: If we could have the next question, please?

AT&T OPERATOR: That will be from the line of Anita Manning with USA Today. Please go ahead.

QUESTION: Hi. Thanks very much. I'll try to be fast. So the reason the virus is worse this year in--in the Gulf State areas is because it's had a year to amplify? Is that what you're saying? And is that likely to continue? In other words, next year will it be bad like this again?

DR. PETERSEN: Okay. That's a very good question. The reason why outbreaks of arboviral diseases such as West Nile virus or diseases spread by mosquitoes are bad in certain areas one year and not so bad in other areas the next year is--is very complex. These are very complex biological systems that are very hard to predict when and where cases are going to occur.

The fact that the virus was there last year just gave it more of an opportunity to re-emerge in a bigger way this year, simply because there was a lot more virus present in that geographic area at the beginning of this year when the viral amplification cycle started, when mosquitoes re-emerged, than the previous year.

MS. HAYES: If we could take the next question, please.

AT&T OPERATOR: Our next question from the line of Elizabeth Cohen with CNN. Please go ahead.

QUESTION: Hi. This is actually Marianne Felder (ph), Elizabeth's producer. Elizabeth had to step away. I have a question that you may have answered in previous calls, but I--please indulge me. It's something that I get asked all the time.

If I--let's say I get bitten by a mosquito this year and it carries the West Nile virus, even if I don't get super-sick or maybe if I do, next year I get bitten again, do I have protection? Has my immune system built up enough protection to protect myself? Or am I vulnerable every year every time I get bitten?

DR. PETERSEN: The answer is, is that you are probably protected. What--we don't have a long--you know, 50 years of experience with West Nile virus in this country. But what we know from--from epidemiological work done in the Old World suggests that there may be lifelong immunity after exposure to the virus.

QUESTION: Thank you.

MS. HAYES: Next question, please.

AT&T OPERATOR: Next question from the line of Marian McKenna with Atlanta Journal Constitution. Please go ahead.

QUESTION: Hi. Thanks so much for doing the call. Dr. Petersen, given the size of this year's outbreak compared to the past couple of years, can you make any predictions at this point as to how much of a problem long-term sequelae are going to be for the people who are--are contracting very serious disease?

DR. PETERSEN: Right. The--what we know--and there is not a lot of data out there. But what we know is, is that studies done in the Northeast among people with West Nile virus--severe West Nile virus infection, meaning those that were hospitalized, is that a very large proportion of them at discharge have not returned to their baseline level of functioning. Many of them have, you know, such--it has very profound neurological sequelae such as inability to walk.

Studies done at one year after--one year after the 1999 New York City outbreak suggested that more than half of the patients still had very persistent and potentially severe neurological syndromes.

MS. HAYES: Next question, please.

AT&T OPERATOR: Next question from the line of John Lowerman with Bloomberg. Please go ahead.

QUESTION: Yes, thanks for taking my question. I'm wondering--I know that you--you're working with people in Louisiana, and I read in the MMWR today that there's not a lot of local mosquito control effort available is Mississippi, and I'm wondering what the extent of your cooperation with Mississippi health officials, particularly at the local level, is right now. Thanks.

DR. PETERSEN: Well, CDC's main collaboration with Mississippi is with the State Health Department. CDC has collaborated extensively with Mississippi in developing surveillance systems for West Nile virus, and they've also--the State of Mississippi has participated in our meetings to develop the guidelines for the surveillance, prevention, and control of West Nile virus, which are present on our website.

Traditionally, however, mosquito control has been mostly around the country locally funded efforts, and so our extent of the activities with mosquito control have been largely with giving advice on--giving technical advice about mosquito control activities, but the actual nuts and bolts of how it's actually done at the state or local level is largely a state and local responsibility.

MS. HAYES: Next question, please--

QUESTION: Wait, can I get to follow up?

MS. HAYES: I've got to see how many I have in the queue, please.

AT&T OPERATOR: Our next question from the line of Larry Altman with New York Times. Please go ahead.

QUESTION: First, before asking a question, may I make a comment that it makes it difficult for us if you don't have a chance for follow-up questions or you--the moderator interrupts the speaker trying to finish the answer to a question. So if we're going to have these, while I appreciate them, it would be more useful if we can develop them instead of calling back, because when somebody calls back, not only one person's going to do it and you're going to multiply all the problems for everybody. That's just a general statement.

My question is: What have you learned regarding the age distribution in the cases so far? You started off thinking that they were younger. And now what about the vector? Have you learned anything about the vector that seems to be most responsible in this outbreak?

DR. PETERSEN: Yeah, that's an excellent question. The cases this year are significantly younger than in previous years. Why that is the case we don't know. One possibility is simply that our surveillance systems in these states are--are picking up milder cases and, hence, younger cases.

Another possibility is, as you mentioned, that there are differences in the vectors that may be transmitting the mosquitoes and--I mean, virus and for whatever reason younger persons are more heavily exposed than older persons in this area.

We don't know what mosquitoes are transmitting the infection to humans in that area. Historically, looking at St. Louis encephalitis virus, Culex quinquefasciatus, or the Southern house mosquito, is probably a major vector of this virus in that area. And, in fact, most of the West Nile virus I saw in that area that we've collected and the State Health Departments have collected through mosquito trapping have been found in this species of mosquito, which is also known as the Southern House Mosquito.

Whether there's other mosquitoes involved in the transmission to humans in that area which could potentially account for the younger age distribution, is something we're actively investigating right now. But we don't have results on that quite yet.

MS. HAYES: Next question.

AT&T OPERATOR: That is from the line of Guy Taylor with Washington Times. Please go ahead. Mr. Taylor, your line is open. Please go ahead.

QUESTION: This is Guy Taylor. I'm sorry.

I wanted to ask a quick question. We may have covered this. If we have, then dismiss me and I'll read the transcript later. It's about why there's been a decision in a lot of counties, particularly I've noticed it in the Washington area, not to test birds, dead birds that are found, as if it's a concession to the notion that the virus is here and it would be useless to test birds.

DR. PETERSEN: Right. There are a number of reasons not to test dead birds. One of the--and one of the reasons that we're finding right now in many areas is, is that 100 percent of the dead birds that are collected are West Nile virus positive in certain areas. And once you've found that, it doesn't make any sense to keep testing dead birds when you know that all of them are positive.

What we're doing in these kinds of cases is recommending that counties take count. They don't need to test all of these dead birds, but what they should do is keep track of how many dead bird reports there are, because particularly in the Northeast we found that the number of dead bird reports, particularly amount crows, correlated quite well to the eventual risk of human infection.

QUESTION: Thank you.

MS. HAYES: Next question.

AT&T OPERATOR: Thank you. Next we go to Tom Watkins with CNN. Please go ahead.

QUESTION: Of the 154 people on whom you have data, can you tell me how many are men and how many are women, how many were hospitalized, how many are in serious or critical condition, and how many people you had diagnosed at this time last year?

DR. PETERSEN: We do not collect detailed clinical data on all these people routinely, so I cannot comment about the details of the clinical presentations of all of these cases. What I can tell you is, is that the vast majority of them have--were hospitalized with meningitis and encephalitis.

As far as the male to female distribution, I do not have those numbers right in front of me. However, there is a slight predominance of men, like on the order of about 55 percent men, 45 percent women, although I do not have the exact figure. But if you care to call me later, the Press Office here later, we can get those figures for you.

QUESTION: And you have no background on how many were diagnosed at this time last year?

DR. PETERSEN: I do not have the exact number that were diagnosed exactly on this date last year. What I can tell you is, is that depending on the year, between 10 and 15 percent of the people in the--of the cases that occurred between 1999 and 2001, had symptom onset before August 1st. Now, if you notice that in this MMWR, of these 156 people, the vast majority of them actually had symptoms before August 1st.

QUESTION: I guess is, is it getting bigger? There's more cases in people, is that fair to say?

DR. PETERSEN: Yes. We're still on the up slope of the epidemic curve, and if you look at previous years, the peak of disease activity in humans has occurred around the last week of August and the first week of September.

QUESTION: Thank you.

DR. PETERSEN: So in other words we expect ore cases to occur.

MS. HAYES: Next question, please.

AT&T OPERATOR: That is from the line of Christy Fake (ph) with CNN. Please go ahead.

QUESTION: Thank you. I'm curious if there is any chance that some of these cases may actually turn out to be St. Louis encephalitis?

DR. PETERSEN: Some of these cases may turn out to be St. Louis encephalitis. What we will do toward the end of the year is go back and probably on many of these people do more specific tests to try and sort out which are St. Louis encephalitis and which are West Nile virus encephalitis. However, right at the current time we are--based on laboratory findings so far, the people that have been reported with West Nile virus, we believe that most if not all of them actually do have West Nile virus and not St. Louis encephalitis.

On the testing that is equivocal between these two viruses, we are doing additional tests at CDC and Fort Collins to try and sort them out, but of the people that are now reported with West Nile virus, we actually believe that most if not all have West Nile virus, but we won't know the final tally until probably sometime during the winter.

QUESTION: Thank you.

MS. HAYES: Another question?

AT&T OPERATOR: Yes. We have four additional questions in queue. Do you have time to take additional questions at this time?

DR. PETERSEN: I can take as many as people want to ask.

AT&T OPERATOR: Very good. Our next question from the line of Anita Manning with USA Today. Please go ahead.

QUESTION: Thanks for taking follow ups. A couple of Louisiana Senators have called for help from the Air Force, and I understand that that has to be approved by the CDC and FEMA. Do you have any idea how long that takes, that process?

DR. PETERSEN: Whether the Air Force gets involved is not a CDC decision. This is a decision that's made between the Air Force and state or local mosquito control districts.

QUESTION: Okay, thank you.

AT&T OPERATOR: And next we go to John Lowerman with Bloomberg. Please go ahead.

QUESTION: I was just wondering is there any more that you can tel me about why doesn't Mississippi have a local mosquito control if that's in fact the way that mosquito control is normally handled?

DR. PETERSEN: Well, the answer to that question is you'll have to talk to Mississippi about that. I do not have the answer. The general generic statement I would like to make about that is this is a classic case of an ignored problem that has now resurfaced. Over the least several decades mosquito-borne diseases were not thought to be much of a problem any more, and a lot of these mosquito abatement programs has basically dried up or disappeared. So now that West Nile virus has emerged in this country, the ability to deal with this virus is generally less than it would have been 2 or 3 decades ago.

QUESTION: Thank you.

AT&T OPERATOR: And next we go to John Pope with Times Picayune. Please go ahead.

QUESTION: Dr. Petersen, might you have any hunch on why Louisiana is hit so hard, not only in comparison to last year, but also in comparison with its neighbors?

DR. PETERSEN: Well, Louisiana has typically been a state that has had higher levels of arboviral disease than other states, simply because it's in--it's a--an area with a lot of water. It is a southern state with a long mosquito season. And typically the kind of mosquitoes that could potentially spread West Nile virus are abundant in that state.

Now, again, what I mentioned earlier is, is that mosquito-borne diseases like West Nile virus or St. Louis encephalitis virus are very, very difficult to predict. They involve very complex biological systems in nature, that certainly for West Nile virus we don't understand fully yet, and so why does disease that's higher in incidence in one area and not in another is something we don't fully understand, something we would like to understand, but we don't have all the data yet.

QUESTION: Is there a site where we can go to find cases--case counts from last year?

DR. PETERSEN: You want case counts per state?

QUESTION: Yes, sir.

DR. PETERSEN: Yes. The best thing to do would be--and I think most of the information you'd probably want is if you look back through the MMWRs, we had one that had final tallies for last year. And if you look back on those MMWRs, they do have the final case tallies.

Also if you look in the August 6th issue of the Annals of Internal Medicine, I have written an article in there which does have the epidemiological information for the previous years.

QUESTION: Cool, thank you.

DR. PETERSEN: If you don't find all the information you need from those sources, contact the Press Office here and I'll get you whatever you need.

QUESTION: Thank you, sir.

AT&T OPERATOR: And next we go to Seth Borenstein with Knight-Ridder. Please go ahead.

QUESTION: Yes, thank you for the follow-ups. Dr. Petersen, you said 10 to 15 percent of the cases of overall years of offset had symptom onset before August 1. My calculation, looking at your website, that's 123 cases you had by the end of July. Am I wrong to interpret that you're going to be at, near or above 1,000 cases by the end of West Nile season, and does that mean--and do you expect a 10 percent fatality rate, which seems to be about what's been happening?

DR. PETERSEN: Okay. The easy part of your question is what is the fatality rate likely to be. Every year we've found that the fatality rate has been among--this is among people with encephalitis and meningitis. The fatality rate has ranged from 11 to 14 percent. And that's been very consistent.

Now, it may potentially be somewhat lower this year because the age distribution of the cases, for whatever reason, is lower, and age is related to mortality. But I would expect the mortality to be--among the more severe cases, to be somewhere around 10 percent this year as opposed to previous years. Maybe a little less, but somewhere it's going to range in that range when all is said and done.

QUESTION: So are we expecting--do you expect near 1,000 cases though?

DR. PETERSEN: If--

QUESTION: You've had 123 [inaudible] in July.

DR. PETERSEN: If the epidemic curve this year is similar to that in previous years, that would be a ballpark estimate. Now, we don't know, since we've never had a big epidemic in the southern United States, where the peak of the epidemic curve will actually be. I mean if the epidemic curve is lower, I mean earlier in the year, you may find less cases. If it's similar to previous years, yeah, you can make an estimate of potentially 1,000 cases, but it's, it's again very imprecise and I can't predict the future.

What I think it is safe to assume is, is that we can expect more cases and potentially a lot more cases.

The other factor that we don't know is what is the effect of mosquito control? I suspect that the mosquito control efforts that are going on in Louisiana and elsewhere are going to have a major effect on blunting this epidemic. So if in fact those efforts are highly successful, we may see a lot less than 1,000 cases. But the bottom line is we'll see more cases and potentially a lot more in the upcoming weeks.

AT&T OPERATOR: Thank you. We have one question remaining in queue. Next we'll go to Larry Altman with New York Times. Please go ahead.

QUESTION: Yes. Do you have any cases of St. Louis or Venezuelan or Eastern or any of the other types of encephalitis reported in the same areas or elsewhere this year?

DR. PETERSEN: There has been no Western equine encephalitis in recent years in the United States, I mean, human. As far as Eastern goes, in the same area, I'm not sure. I don't think so. There has been a few cases of Eastern reported here, but I do not believe they're in the same areas that were heavily affected by West Nile virus.

As far as St. Louis encephalitis virus, yes, there has been co-circulation of these viruses. And we've most noticed this in parts of Texas.

QUESTION: Are the numbers in keeping with past years?

DR. PETERSEN: For St. Louis?

QUESTION: Yes.

DR. PETERSEN: I think it's still too early to tell, but it's consistent with previous years.

Part of the problem with St. Louis, in trying to determine what's consistent with previous years, is what--along with West Nile, St. Louis has been a disease that occurs sporadically but also occurs in epidemics. And so, you know, the numbers vary markedly from year to year. But this does not seem to be an extraordinarily high year for St. Louis.

MS. HAYES: Are there any other follow-on questions?

AT&T OPERATOR: We have no other question sin queue.

MS. HAYES: Thank you for joining us today. If you've got any follow-on questions later this afternoon, you can contact the CDC Media Relations Division at 404-639-3286, and also the transcript from today's tele-brief will be posted at the CDC Media Relations website later this afternoon. Thank you for joining us.

AT&T OPERATOR: Ladies and gentlemen, that does conclude our conference call for today. Thank you for your participation and for using AT&T's Executive Teleconference. You may now disconnect.

[End of teleconference.]

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