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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
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.
MS. HAYES: I'd like to turn it over now to Ms. Shisler to talk about her
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
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.
MS. HAYES: Great. We'd like to open it now for any questions for these two
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
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
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
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
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
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
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
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
MS. SHISLER: The CDC's Kids Walk--
QUESTION: Is this Jessica, or is this--who's talking now?
MS. SHISLER: This is Ms. Shisler.
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
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
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
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
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
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.
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
DR. PETERSEN: I'm a little confused by your question. Are you talking
about vaccination for horses or 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.
DR. PETERSEN: But the proportion of those who get infected, who go on to
develop more severe disease is highly related to age.
DR. PETERSEN: The older you are, the more likely you are to develop severe
West Nile disease.
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
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
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
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
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
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
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
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
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
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
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
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,
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
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
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
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
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?
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.