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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.


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.

Listen to the telebriefing

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