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CDC Telebriefing Transcript
West Nile Virus Activity Update
August 22, 2002
CDC MODERATOR: Thank you, John, and welcome to everyone for the weekly MMWR
telebriefing where today we'll have Dr. Lyle Petersen, and that's spelled
P-e-t-e-r-s-e-n, Dr. Lyle Petersen who's a medical epidemiologist in our
national Center for Infectious Diseases here at CDC.
He'll be talking today about the MMWR article, West Nile virus
activity in the United States 2002. He'll provide a brief opening and then
we'll open it up to Q&A.
Dr. Petersen.
DR. PETERSEN: Thank you.
CDC continues to work with state and local health departments to help
control West Nile virus. As of 9:30 Eastern time yesterday, there has been
a total of 270 human cases of West Nile virus infection reported to CDC
from 12 states, the District of Columbia and New York City. [UPDATE: as of
August 22, 2002 3pm ET, the current case count is 296 human cases of West
Nile virus infection reported to CDC from 15 states, the District of
Columbia and New York City. There have been 14 fatalities.]
There have been 13 fatalities reported. Please refer to your MMWR
for a state by state breakdown of cases.
CDC currently has about a dozen staff in Louisiana, Mississippi, or
Alabama, working side by side with state and local health officials. They
continue to look for cases and trap birds and mosquitoes as well as study
the clinical presentation of the disease in humans.
I would also like to remind everybody that HHS Secretary Tommy Thompson
announced yesterday the availability of additional funds being awarded to
states to help control West Nile virus. HHS is providing an additional $4
million through the CDC to states hardest hit by West Nile virus.
The 4 million is in addition to the 10 million that was made available to
states two weeks ago to help strengthen their efforts to combat the virus.
The additional money brings CDC funding to states for West Nile virus so
far this year to more than $31 million.
Thank you, and I'd be glad to answer questions at this time.
AT&T MODERATOR: And ladies and gentlemen, once again, if you do have a
question at this point please press the one.
Our first question is from Marian Faukle [ph] with CNN. Please go ahead.
QUESTION: Hi. I have two questions for you. Number one, the Georgia case
that made local news here and hasn't been confirmed by CDC yet.
The question I have related to that is according to the local reports and
what the hospital is telling us, the sample, the blood samples were sent
to CDC, I think it was August 7th. Wouldn't you know by now if this is a
confirmed case or not?
So how long does it take? And then the second question I have has
something to do with hunters. Are hunters people who would catch, or shoot
an animal that has West Nile, while they're butchering it--I know
that--I've been told that ingesting won't cause the transfer of disease,
but if while butchering, blood transfer, is that a possibility? And have
you issued a warning to hunters, and if so, which way, and which states?
DR. PETERSEN: Okay. Let me take your first question first about the
Georgia case. CDC is working with the Georgia State Health Department on
investigating a number of potential cases of West Nile virus infection in
humans.
To date, the samples that CDC has received from Georgia, have been
negative so far. There are a number of other samples that either have been
received by CDC or are about to be received by CDC, that are being or will
be in the process of being tested. As for the hunters, CDC has guidelines
for hunters out on its Web site right now.
The degree of infection in animals for West Nile virus is yet to be
determined, so we do not know how many animals, at any given time, may be
infected with the West Nile virus.
We know that the infection is primarily an infection of birds and whether
game animals that hunters would normally be hunting have any degree of
West Nile virus in them at all is unclear.
We would recommend that hunters take the normal precautions they should
take to prevent any kind of infection from butchering these animals, and
we would certainly recommend that hunters would not be, would take
precautions to have undue exposure to the blood of any animal, just not
due to West Nile but due to other potential pathogens as well.
CDC MODERATOR: Next question, please.
AT&T MODERATOR: And that's from John Pope, the Times-Picayune New
Orleans. Please go ahead.
QUESTION: Good morning. Dr. Petersen, you mentioned the $4 million
announced yesterday. I have two questions on that. How much is going to
Louisiana which leads the nation in human cases, and does that have any
effect on other money that the state is trying to get from the Federal
Government?
DR. PETERSEN: CDC so far has awarded $3.4 million to Louisiana.
QUESTION: Right. But does this money that's announced yesterday, will any
of that be coming to Louisiana?
DR. PETERSEN: I do not have the answer to that question right now and I
would suggest that you follow up with our press office for an answer to
that.
QUESTION: Okay; all righty.
CDC MODERATOR: Is that it, John? Next question, please.
AT&T MODERATOR: Thank you. A question from the line of Robert Leehunt
[ph] with LA Times. Please go ahead.
QUESTION: Yes. Dr. Petersen, I wonder if you could kind of address the
vector question for a moment and describe for us the limits of the
westward expansion of the virus at this point.
DR. PETERSEN: Well, right now, the furthest west we know that the virus
has gone has been to Wyoming and Colorado. We fully expect that, over
time, the virus will make it to the West Coast. What the timing of it will
be is unknown at this time. It's unknown whether the virus will make it to
California or the West Coast this year or next year or the year after
that. It's completely a matter of conjecture.
However, if you remember that St. Louis encephalitis, which is a very
closely related virus to West Nile Virus, and which has been endemic in
this country for years, this is a coast-to-coast virus. And what we know
about St. Louis encephalitis virus and West Nile Virus is that they often
share the same mosquito vectors, and so because of that, we would expect
that the virus would be able to thrive quite well on the West Coast, as
well as it has elsewhere in the United States.
CDC MODERATOR: Next question, please?
AT&T OPERATOR: And that's from the line of Marilyn Marshione [ph] with
the Milwaukee Journal. Please go ahead.
QUESTION: Hi, Dr. Peterson. Thank you for continuing to hold these
briefings.
I have two questions. I wonder if you can talk a little bit about how many
samples CDC has yet to isolate or confirm, roughly, how many have you
received from other states that you're looking at or that have not yet
been ruled positive or negative.
And then, also, secondly, is there anything that you or other CDC
officials working on this outbreak this year suspect is different about
why the West Coast, where this originated in '99, has been experiencing
relatively few cases this year?
DR. PETERSEN: Both of those are excellent questions. Let me first address
the question about how many samples our laboratory is currently
processing.
I actually do not know that number off the top of my head, and the number
of samples that our laboratory is processing ranges from day-to-day. Don't
forget that our laboratory is testing humans, birds, and other animals so
that the actual number of human samples, I do not know right off the top
of my head. I can tell you that our laboratory is quite active right now.
Now, as far as the pattern of infection this year in the United States and
why the Eastern United States does not seem to be as heavily affected. I
have a couple of thoughts on that.
The first thought is, is that West Nile Virus is likely to be similar to
the St. Louis encephalitis virus in its epidemic pattern, and that is what
we would expect, over time, is to see sporadic cases of the virus
appearing throughout the country with occasional epidemics which can
sometimes be large, and this is the pattern that's been observed with the
St. Louis encephalitis virus, which I mentioned earlier is a related virus
endemic in this country.
This pattern has also been observed in the Old World in temperate climates
where the virus has been endemic for years, and years and years. So it's
not surprising that we would see different levels of activity in different
parts of the country.
My other thought on this is that if you look at the pattern of infection
this year, as compared to the last three years, where we've had the virus
in the United States, what we've characteristically seen is that human
infections start becoming increasingly reported about the middle of
August. As I mentioned in previous teleconferences, that infections will
peak at the end of August and the beginning of September, if this follows
the same pattern as previous years.
So the fact we're starting to see West Nile Virus in more states,
including some of the Eastern states, is typical of what has happened in
the last years. What is different about this year has been the very early
onset of a lot of cases in Louisiana, Texas, and Mississippi.
So the rest of the country is actually behaving like we might expect it to
behave, it's just that this year was abnormal because of the large number
of cases in Texas, Louisiana and Mississippi.
Did that answer your question?
QUESTION: It did. I wonder if I could ask one more follow-up and that is
the nature of the knowledge about immunity, what leads us to believe that
exposure to West Nile one year would confer immunity in the next.
DR. PETERSEN: What we don't know is whether being exposed to the virus
will cause lifelong immunity. What we do know is from related viruses,
like Japanese encephalitis, for example, or yellow fever, that once you
get infected with those viruses, you have immunity for life, and so we
might expect the same thing to occur with the West Nile Virus.
In addition, in areas of the world where the virus is highly endemic, like
in parts of Africa, like in the West Nile district, for example, that what
you see is this infection primarily in children, and you don't see the
infection so much in adults, and that would lead one to believe that
people get infected at an early age and then become immune for life.
CDC MODERATOR: Next question, please.
AT&T OPERATOR: It's from Julie Dierdorf [ph], Chicago Tribune. Please
go ahead.
QUESTION: My question was about the children getting it. This year we've
had a two-year-old and a three-year old. My question, before you just said
that last statement, was why haven't we seen more children with it, but
maybe I guess can you just answer that--why we're not seeing more cases
with young children.
DR. PETERSEN: Yes. As I mentioned earlier, that this is primarily an
infection, excuse me--the disease occurs primarily in older individuals.
Persons age 50 and above, in particular, have increased risk for
developing severe complications of the disease.
What we've seen from previous sero-surveys or previous studies where we've
looked at population groups, the actual exposure to the virus appears
relatively constant among age groups, but what is actually different is,
is once you get infected with the virus, your chances of developing more
severe disease seem to be higher in older individuals.
Now the fact that we found infections in children is not surprising
because, as I mentioned, everybody is susceptible to getting mosquito
bites, and everybody is susceptible to getting infected with the virus,
but the main point is, is that once you're infected, that a larger
proportion of those infected will be older individuals. But, again, you
could expect some symptoms in any age group. It's just a matter of what
your probability is of developing severe symptoms.
QUESTION: In Africa and not here?
DR. PETERSEN: Excuse me?
QUESTION: You mentioned before that it is seen in children overseas. In
places like Africa, you said it's an infection primarily in children, not
so much in adults. Why don't we have that same pattern?
DR. PETERSEN: Well, what you see in places like Africa is you see that it
is primarily an infection of younger people, and what we think is
happening there is, is that the older individuals are already immune to
the disease, but in Africa, the symptoms are very mild or people have no
symptoms at all. And that's pretty much what we're seeing here. People,
younger children infected with this virus, the vast majority of them have
no symptoms at all or just have mild illness.
QUESTION: Okay, thanks.
CDC MODERATOR: Next question, please.
AT&T OPERATOR: That's from Maryn McKenna with the Atlanta Journal
Constitution. Please go ahead.
QUESTION: Hi. Thanks for doing this.
Dr. Peterson, I've got two questions. I'll ask them both at the same time.
First, a few minutes ago you were talking about the behavior of the virus
in humans in the Old War versus the behavior over the past couple of years
in America. So my first question is, looking at research that was done on
the virus's behavior in the Old World, is there any significant difference
in the mortality rate compared to the number of people infected in the
epidemics in the Old World versus what we're seeing in the U.S.,
particularly this year?
My second question is, given that it's expected that the virus is going to
continue to move across the continental U.S., can you look ahead and see
any other geographical area where the local ecology might contribute to a
particular bloom of infections in the way that it apparently has on the
Gulf Coast?
DR. PETERSEN: Let me take your first question first about mortality rate
in the Old World versus the New World.
Characteristically, this virus has been known, since the virus was
discovered in the 1930s, to cause periodic outbreaks, as I've mentioned
before. Most of these outbreaks have been relatively mild disease, and
they've been mostly noted in young people, like military recruits, for
example, with one exception. There was an outbreak in 1957 in Israel in
which there was severe neurological disease associated with an outbreak
that occurred in a nursing home.
So mild outbreaks continued to be reported until about the mid-1970s, both
in the Middle East and in Africa. And then from about 1975 through to
about the mid-1990s, there really was no major outbreaks reported of this
virus. And then, starting in the 1990s, there seemed to be the
re-emergence of outbreaks, but also outbreaks associated with more severe
disease, meaning severe neurological disease in humans, particularly older
humans. And these outbreaks have been noted in the United States,
naturally, but also in Israel, Romania, and Russia.
So the pattern of severe disease seems to have changed sometime around the
mid-1990s. The reasons for this are still unknown, and we're trying to
sort this out.
And I also might add that there are number of strains of West Nile virus
circulating throughout the world. And all we know is that strains that are
circulating in Africa have not been associated with severe neurological
disease like they have in the outbreaks that I have just mentioned.
Now, as far as the geographical areas where we would expect maybe a bloom
of infection, as I mentioned earlier, we expect the disease to cause
periodic outbreaks, which may be sometimes large. Where these outbreaks
will occur is really a matter of conjecture. If you look at St. Louis
encephalitis virus over the last 50 years or so that people have been
studying it, a lot of very smart people have put energy into trying to
figure out what are the predictors of big outbreaks, and nobody's come up
with a very good predictive model. And the reason for that is because
these diseases in nature are incredibly complex and involve very
complicated ecological systems.
Now, where we might expect the virus to cause a bloomer of infection, or
let's--I think what you're alluding to is an outbreak--all we can say is
that we know that in the southern United States these kinds of outbreaks
of St. Louis encephalitis are more common. So we would expect that
probably over the long run there may be more West Nile virus activity in
the southeast of the United States, but that outbreaks could potentially
occur anywhere.
CDC MODERATOR: Next question?
AT&T MODERATOR: And that's from Larry Altman, New York Times. Please
go ahead.
QUESTION: Yes, well, is the pattern of seeing cases in younger people
still holding up? That was there originally, and I was just wondering,
with the greater number of cases, if that pattern's still holding.
DR. PETERSEN: We still are seeing younger people. The median age is still
this year about in the mid-50s, which is about a decade younger than in
previous years. We do not know the total reasons for that. But one of the
reasons for that is a very strong possibility is simply that our
surveillance system has gotten better and better and that we're picking up
milder disease. As I mentioned earlier, milder disease is associated with
younger age. And so if we're going to pick up milder diseases, we're going
to--the average median age is going to be less than in previous years.
We're still in the process of trying to analyze these data. It's a matter
of importance to us to figure this out.
CDC MODERATOR: Next question?
AT&T MODERATOR: And that's from John Aman [ph], Bloomberg News.
QUESTION: Thanks for taking my question. I'd like to go back to the vector
again, to the mosquito for a minute. I'm wondering if there's any concern
about the use of permethrin for insecticides. Have we seen an increase in
resistance, are we likely to see any increases in resistance, given
widespread spraying? And how important is it to continue to kill
mosquitoes if all the mosquitoes that we're seeing are--I've heard this is
true in Louisiana--if all the mosquitoes, the remaining mosquitoes, are
infected with the virus despite the spraying? Thanks.
DR. PETERSEN: As far as far as resistance to permethrin or insecticide, I
do not currently have data on this and I would like to refer you to the
EPA for more information. You can also get information about this from our
national guidelines, which are available on our website, which has a
detailed discussion about insecticide resistance.
CDC MODERATOR: Caller, why don't you clarify your second question? I'm not
sure that we understood the question.
QUESTION: Yeah. I spoke with mosquito management people in Louisiana, and
they said that the number of mosquitoes--because of their spraying
efforts, the number of mosquitoes are actually less than a tenth of what
they normally are. But the problem is not the number of mosquitoes, but
the widespread--I guess you'd say the prevalence of West Nile virus in the
remaining mosquitoes. In other words, all the mosquitoes have West Nile
virus; they can't kill every single mosquito in the state.
DR. PETERSEN: Exactly. There's really two issues here, as you point out.
One is the absolute number of mosquitoes, and the second thing is what
percentage of the mosquitoes are infected. And both of those relate to the
probability of a single person coming in contact with an infected
mosquito.
Mosquito control efforts will greatly knock down the number of mosquitoes.
You cannot get rid of every mosquito around you, as anybody who's lived in
the South knows, but it's a matter of decreasing people's probability of
getting in contact with an infected mosquito. And one way to do it is just
knock down the number of potential vector mosquitoes as much as possible.
And that's what these mosquito control programs are actually doing. You
can't get rid of every mosquito, unfortunately, but at least you can
decrease the number so people's probability of coming in contact with an
infected mosquito is decreased.
Now, you're right about the infection rate in mosquitoes--in part. In any
given situation with a vector-borne disease like West Nile virus, not
every single mosquito is infected with the virus. In fact, most of the
time a very small percentage, usually 1 percent or less, is infected with
the virus. With West Nile virus in certain areas we've noticed a higher
percentage than 1 percent, but it's certainly not on the range that every
single mosquito is infected.
So it still is that a small percentage of the mosquitoes are infected. The
fact that this year we've seen, in many areas, a higher percentage than
usual infected with West Nile Virus, it just gives added reason to try and
control the number of mosquitoes as much as possible, and that's what
these mosquito control districts are doing.
CDC MODERATOR: Next question?
AT&T OPERATOR: Debra Rosenberg from Newsweek, please go ahead.
QUESTION: Hi. I was wondering about some of the new trends that you've
mentioned, both the virus showing up in younger people and the earlier
onset of the infections this year. Does that lead you to wonder about
different strains of the virus? You mentioned that there were many strains
around the world? Do you think that could be a factor here?
DR. PETERSEN: What we know is that in the United States, so far, a single
strain has been circulating, which makes sense. We think that one strain
of the virus was introduced. We think it probably came from somewhere in
the Middle East because it's very similar to strains that have been
circulating in that area of the world, and that strain has simply
propagated throughout the United States. So there is no evidence at all
that this virus has changed at all or that there's multiple strains of the
virus circulating.
Again, I think I would like to make the point that the reason we're
probably seeing younger people this year is that we're picking up milder
illness through our surveillance systems.
CDC MODERATOR: Next question, please.
DR. PETERSEN: And that's from Sabrina Gibbons with WSB Radio. Please go
ahead.
QUESTION: This is Terry Brown. Sabrina had to step away.
We were curious about we had a report here in Metro Atlanta, a man's
family told us that the CDC had confirmed he had West Nile Virus, and his
doctor said the CDC had told us that, but apparently this morning they
were saying that they had not confirmed this case. Could you clear up the
question there?
DR. PETERSEN: The CDC has not confirmed any laboratory test results from
humans in Georgia this year, but, as I mentioned earlier, that there are
some in various stages of being tested or being sent to CDC.
QUESTION: Okay. So you don't know where the doctor got the impression that
the CDC had told him they had confirmed this?
DR. PETERSEN: I cannot speculate on where people get their information.
QUESTION: Okay.
CDC MODERATOR: Next question, please.
AT&T OPERATOR: That's from the line of Lee Hopper with the Houston
Chronicle. Please go ahead.
QUESTION: Thank you. This goes back to the number of children infected and
showing symptoms. I just wanted to see if you could clarify, do you think
that there are lots of young children that are infected, but they just
don't get sick?
DR. PETERSEN: Yes, I do. As I mentioned earlier, that mosquitoes bite
anybody, and so the studies that we've done so far in the United States,
mainly up in the Northeastern United States, show that the infection rate
among age groups is fairly constant. We do not have a lot of information
about infection rates in very young children, but we would suspect that
they would be similar to anybody else.
So infection rates among people, by age, are probably very similar this
year, like we've found in previous years. What is different, though, is
that people, and older individuals have a higher tendency to get symptoms,
and more severe symptoms. That's the general pattern that's occurred in
the last three years, and we think it's the same way this year.
CDC MODERATOR: John, how many more questions are in queue?
AT&T OPERATOR: We still have seven participants in queue.
CDC MODERATOR: We'll take questions for maybe five or ten more minutes. Go
ahead.
AT&T OPERATOR: Next question is from Adam Marcus with Health Scout.
Please go ahead.
QUESTION: Hi. I apologize if you've already answered this question, but is
there any way to estimate, from the number of confirmed cases and the
number of infected mosquitoes, what the possible total caseload might be?
DR. PETERSEN: I cannot speculate on that. What I will do is give you a
couple of facts.
One is that, overall, we have found--and this has been very
consistent--that of all of the cases of encephalitis and meningitis, there
are probably about 150 more people who have become infected.
So a rough calculation one could make is that, let's say, if you have 10
cases of encephalitis or meningitis, that about 1,500 people have actually
been exposed to the virus. We've done a number of sero surveys, both in
the United States and in Romania, and have found this to be a very
consistent finding.
Now we've also found, from our serological surveys that have been done in
New York City during the 1999 outbreak, that suggest that about 20 to 30
percent of those persons who do become exposed to the virus, and infected
with the virus, develop some kind of mild symptoms.
QUESTION: Thank you.
CDC MODERATOR: Next question, please.
AT&T OPERATOR: That's from Robert Bazell, NBC News. Please go ahead.
QUESTION: Hi. Two related questions.
One is the number of cases doesn't seem to have changed much in the last
week, and should we read anything into that about either the epidemic
slowing down or perhaps the labs backing up?
And the second thing is, in terms of your case definition, if you happen
upon somebody who has a mild flu-like illness, and for whatever reason
they manage to get tested for West Nile, are they considered a case or
does somebody have to have encephalitis or meningitis?
DR. PETERSEN: We are taking reports of anybody who has laboratory evidence
of West Nile Virus infection, and what evidence is required is detailed in
our guidelines that are on our website, regardless of clinical symptoms.
Now, this year, we have noticed a higher proportion of the cases reported
to us than previous years to have milder symptoms. Again, this is why we
think that the age distribution this year may be younger than previous
years.
Now, as far as the potential leveling off of the epidemic just because
there have not been as many cases possibly reported this week as previous
weeks, I cannot speculate on. There are many factors which determine how
many cases are reported on a given day. One factor is how much the state
laboratories are--how many of these specimens the state laboratories are
asking CDC to confirm, for example, which will cause some inherent delay
in the system.
Other factors may include just the timing of the laboratory testing in
laboratory, as well as a number of other factors, which could influence
exactly when cases would be reported.
What I would say for sure is, is that judging from the number of cases
reported on a day-to-day basis is not going to be very accurate. I think
we have to look over a longer period of time to look for a trend.
QUESTION: Thank you.
CDC MODERATOR: Next question, please?
AT&T OPERATOR: That's from April Nelson, CBS, Atlanta. Please go
ahead.
QUESTION: Thank you. Yes, I have a couple of questions.
One, the medicine used to treat West Nile Virus, can it be used as a
preventive, and is there any thought being given, since we're seeing more
cases, of like mass inoculation?
DR. PETERSEN: Okay. I would like to be very emphatic about two points. One
is that there is no vaccine for this disease, so there is no need for mass
inoculation. There are vaccines under development, but they will be a
number of years off before they could ever be applied to the general
population.
The second thing is about medicine for West Nile Virus. There is no
specific proven treatment for the treatment of West Nile Virus infection.
There are some experimental protocols that are out there. The one that is
probably being applied most this year is the experimental protocol for the
use of alpha interferon, which was just allowed by the FDA to proceed as
of yesterday, but that is it. There is no proven medicine for West Nile
Virus infection.
QUESTION: So how do you treat the disease?
DR. PETERSEN: The treatment of the disease is supportive. Many of these
patients require ventilatory assistance or help breathing in the intensive
care unit, but basically it's supportive care.
QUESTION: Thank you.
CDC MODERATOR: Next question, please?
AT&T OPERATOR: That's follow-up from Miriam Falco. Please go ahead.
QUESTION: You answered one of my questions on alpha interferon, so thank
you.
One more question. Based on where you're seeing the reports of animal
cases, and the bird cases, in particular, the amount, you said the
Southeast seems to be harder hit this year than in previous years. Are
there any other areas that you expect you might see more this year,
besides the Southeast?
DR. PETERSEN: Well, I can't tell you, to answer your--let me start over
again. I cannot precisely answer your question for every part of the
United States. What we are seeing in many areas of the United States is
viral activity that is similar or greater than in previous years,
particularly in the Southeastern United States, but I think what I'd do is
I'd prefer to have you go to state and local health departments for
locally specific information.
QUESTION: But would you say--how does it compare August 2002 to August
2001, overall, when you look at the numbers?
DR. PETERSEN: As far as?
QUESTION: Nationwide.
DR. PETERSEN: As far as infections in birds, for example?
QUESTION: No, in humans.
DR. PETERSEN: In humans. As I mentioned earlier in the telecast or in the
conference here this morning, was that what is unusual this year is the
large number of humans that have been infected in Mississippi, Louisiana,
and Texas earlier in the year. Infections in those states began to appear
in the middle of June. The earliest infections we noticed in humans,
before this point, was in the middle of July. So infections started
appearing about a month earlier.
What we see for the rest of the country is human infection starting to
appear in various parts of the country. This is the time of year we would
expect to begin identifying infections in humans if it were a normal year.
What is different about the rest of the country this year is that
infections are being noted in humans in more and more states. So we can
expect that, since we know that the virus has spread.
CDC MODERATOR: John, we'll take one more question, please.
AT&T OPERATOR: That's a follow-up from Robert Lee Hobbs. Please go
ahead.
QUESTION: Thank you, sir.
I wonder, and perhaps this is appropriate as a concluding thought, if you
would put West Nile virus, and the activity in the last three years, in
the context of a broader pattern of emerging diseases.
I mean, there have been a number of instances in the last decade or so
where previously, I don't want to say unknown, but not significant
diseases have kind of found a new foothold in the United States due to
various kinds of ecological or environmental or lifestyle changes, and I
wonder how West Nile Virus fits into that context.
DR. PETERSEN: West Nile Virus fits very well into that context, and I
think I'd like to put that into the context of vector-borne diseases in
general or diseases spread by insects.
If you look at the pattern over the last decade or the last century, you
will see that these viruses have been imported over the centuries as
commerce, and trade, and travel and human movement has progressed
throughout the world. Examples would be yellow fever and dengue were both
introduced into the United States more than 100 years ago. They were since
eliminated, for the large part, out of the United States due to mosquito
control activities.
But if you look at dengue, which is probably the recent problem we've had
here in the Americas, you know, this is an imported infection into the
Americas. It was largely eliminated back in the 1960s, and late 1950s,
because, through the use of DEET in controlling aedes egyptae, which is
its vector mosquito.
But since then the virus has come back in full force and has caused
hundreds of thousands of infections even in the last year throughout the
Americas, and is basically on our border. We had an outbreak with this a
couple of years ago in Texas, on the border of Texas and Mexico.
So all of these vector-borne diseases are basically reemerging and, in
part, due to the movements of people, movements of commerce, as well as
the human populations increasing in density and encroaching on natural
habitats where these infections naturally occur.
CDC MODERATOR: John, I think we need to conclude. I appreciate everybody
joining us on today's MMWR telebriefing. Any follow-up calls or
questions can be directed to the main CDC Press Office at 404-639-3286,
and we'll do the best we can to answer all of the questions.
I want to remind everyone to continue to check back to the CDC website for
period updates on West Nile Virus.
Thank you.
Ladies and gentlemen, that does conclude your conference for today. Thank
you for your participation, and you may now disconnect.
