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CDC Telebriefing Transcript

West Nile Virus Update

August 5, 2002

CDC MODERATOR: Thank you, Cindy, and thank you all for joining us today for this telebriefing.

We have with us Dr. Julie Gerberding, the director of the Centers for Disease Control and Prevention, and DR. James Hughes, director of CDC's National Center for Infectious Diseases.

Dr. Gerberding will be providing some opening comments and providing an update on the West Nile outbreak in the United States and will follow that with some Q&A.

So at this point I'd like to turn it over to Dr. Gerberding.

DR. GERBERDING: Thank you, Tom.

Let me just say thanks to everyone for joining us on this call. The goal of the call is really to give you a chance to get some information about the West Nile virus epidemic and also for us to provide you with an oversight of what we are doing and where we are right now, and where we expect to go over the next several days.

So let me just start with just a brief recap.

The current situation as we know it today is a total of 88 cases that have been reported, 58 in Louisiana, 22 in Mississippi and eight in Texas.

In addition, there are four deaths that attributable to the infection. Thirty-four states have recognized West Nile virus in mosquitoes or birds, and those states are primarily in the East Coast of the United States. So far we have no documented activity of West Nile virus west of a line that roughly extends from about Winnipeg to Houston. So it has moved east and south over the last two years but it is not yet known to be affecting the West Coast, and obviously we have the bird evaluation and mosquito evaluation programs going on in the states to identify movement of the virus because infection in mosquitoes and birds is the best sentinel for where we might see future human cases, and gives us the early alert that vector control programs need to start in those areas to reduce the chance of human cases.

Let me just remind you all of what we are talking about here in terms of West Nile virus illness.

It's very important to appreciate that of the people who are actually known to become infected with the virus as we detect it through antibody testing, only about one in five of those infected people will have any clinical sign of the illness at all, or any fever, or any awareness that they've been exposed, and only one in 150 infected people will develop the more serious complications.

So most people who are exposed to the mosquitoes or the virus are perfectly well and have absolutely no complications.

In this particular set of cases that have been diagnosed in Louisiana, Mississippi, and Texas, we're a little concerned because the cases are appearing a bit earlier in the year than they have in the past, and that there's a suggestion that maybe some of the people with the encephalitis syndrome are a bit younger than the patients in the previous years, but it's really too early to say for sure whether there's any change or evolution in the pattern of the outbreaks.

We are certainly impressed with the excellent job that the state and local agencies are doing in preparing and responding to West Nile. I think it's an example of how the investments that have been making since 1999 have really paid off. Some of the things that have been done in the states include expanding the capacity of the laboratories to actually accurately diagnosis West Nile virus.

You know, keep in mind, we didn't even have this virus here prior to 1999, and today the states have done just a very accurate job of detecting and confirming their specimens as being West Nile.

In addition, the clinicians are recognizing cases and reporting them effectively, and we have a great network called ArboNET which allows us to track the epidemic and to share information among various health agencies as we go, and certainly, and perhaps most importantly, the programs to control the mosquitoes in the affected areas are in full swing and certainly contributing to reducing the impact on human health.

So one of the real important messages we want to get out to the public, that while we're concerned about the increase in cases, and we want to do everything we at CDC can do to support the program for mosquito control, there's no need to panic. We're not in a crisis mode. This is certainly not unexpected evolution, based on what we've learned in the last three years, and it's certainly one that we have been working toward responding to with the investments that have been made so far.

I think people need to appreciate--again, no need to panic--but some common sense measures that individuals can take, that will help protect themselves or their families, and most importantly in that is to kind of inspect their property and look for stagnant water, which is a breeding ground for mosquitoes. Just empty out vessels, children's toys, flower pots, things like that that hold water in a stagnant state.

In addition, wear loose clothing or cover the skin when spending time outdoors, and, finally, using a insect repellent, preferably one that contains DEET.

And just a quick reminder, for children, the concentration of DEET should probably not exceed 10 percent, but for adults, 10 percent up to 50 percent is a very effective way to deter mosquitoes.

I'd also like to remind you in terms of encouraging the public with questions to contact CDC.

We've set up quite a few systems to facilitate that contact. One is our toll-free number for general questions. That number is 1-888-246-2675, and for those who are Spanish speaking, the number is 1-888-246-2857.

And also our Web site is, and to remember that the most important resource for managing this is really at the level of the local or state health department, and the folks there are in the best position to know what are the appropriate measures, and what's really happening in a specific region of the country.

So with that, let me stop and offer to take questions, and Dr. Hughes will certainly be serving as a expert scientist and can help address questions that specifically relate to the details of West Nile.

CDC MODERATOR: So Cindy, with that I think we'll say can we have questions, please.

AT&T MODERATOR: Thank you. Ladies and gentlemen, if you wish to ask a question, please depress the one on your touchtone phone. You will hear a tone indicating that you have been placed in queue. You may remove yourself from the queue at any time by depressing the pound key.

If you are using a speaker-phone, would you please pick up your handset before pressing the numbers. And for our first question we go to the line of Seth Bornstein [ph], Knight-Ridder. Please go ahead.

QUESTION: Yes. Dr. Gerberding, thank you so much for doing this.

A question on the younger onset. Can you tell us, last week the median age was 57, and I believe--can you tell us what the median age pre this year's outbreak has been, and looking with all the new cases, what is the median age of the victims right now, and I know you've had as young as eighteen.

Can you tell us, for example, how many of these are under forty, which is--

DR. GERBERDING: I can't give you those details right now because we're just getting the early information from some of the cases that are included in the total of eighty-eight.

So as we get the details of those cases into the ArboNET, we'll be able to give you more specificity on that; but not today.

QUESTION: Okay. Can I just follow up then. In terms of--you said this is not unexpected, but it is earlier, it is younger, and is spreading further west.

Considering all the other health issues that are always out there, and seasonal, how would you put this in perspective to some of the other health issues out there, that we get in the summertime?

DR. GERBERDING: Well, you know, I'll let Dr. Hughes respond to this as well, but I think this is something we're going to have to learn to live with because this virus is very well-established now in the bird and mosquito population, and so as we study the patterns of migration of birds and the patterns of mosquitoes, I think we could use some common sense and kind a predict that where mosquitoes go, this is going to be a problem.

So the fact that it's gone further into the south and further west is really very consistent with what we understand about the biology of the organisms that contain it.

You know, this is something that we want to stay on top of. It's a focus, one of the many focuses of CDC prevention and control activities, but it fits into the overall framework of our capacity to respond to emerging infectious diseases, regardless of whether they're naturally acquired or bioterrorism in origin.

QUESTION: Thank you.

DR. GERBERDING: Now I should just add to that, that because we feel that this is part of business as usual for us, and we want to continue to provide the optimal coordination of things going on in these various jurisdictions, we're handling this particular situation through our Operations Center at CDC. So we'll be coordinating things using some of the same frameworks that we might use for true public health emergency, but it I think illustrates the dual function of the various investments that we've made in preparedness and response capacity over the last couple of years.

QUESTION: So even though you used the word epidemic earlier, you don't consider this a true public health emergency at the moment; right?

DR. GERBERDING: I think we don't want to overstate the situation. This has been an evolving problem since 1999, and we see it expanding into new areas, so there's a certain sense of urgency in making sure that the response is optimized; but I don't think we need to send a message that we're dealing with a crisis.

CDC MODERATOR: Cindy, to get as many reporters asking questions as possible, we'll limit it to one question and one follow-up from each reporter. So next question, please.

AT&T MODERATOR: Thank you. The next question is from Erin Hayes, ABC News.

QUESTION: Yes; thank you again.

I understand that for West Nile virus, typically, August and September are the months when you see the highest number of cases.

What are you anticipating over the next few weeks in terms of an increase in the number of cases and/or deaths?

DR. GERBERDING: Jim, do you want to take that question?

DR. HUGHES: Sure. You're right. In the previous years, the bulk of the human disease activity has occurred between mid-July and mid-September. The onset of the first cases this year actually occurred in mid-June. So a month or so earlier than we'd seen in the three previous years.

Given that the focus has shifted to the south and to the west, this really is not that surprising, given the differences in climate, the differences in bird populations, and the differences in mosquito populations.

I would just further emphasize that this is an excellent example of an emerging vector-borne disease, with introduction initially into the New York City area, and then movement, as Dr. Gerberding has said, to the south and to the west.

The disease will not necessarily behave exactly the same in all geographic areas.

QUESTION: What are you anticipating, though, in terms of caseload over the next couple of months? I mean, you have 88 cases so far. I realize I'm asking you to sort of extrapolate and predict; but what do you expect?

DR. HUGHES: Well, we have more cases already this year than we have had in any of the previous three years, so this will be obviously a peak year. Given that we're early still in the transmission season, we are concerned that we'll see more cases and it highlights the need to continue to work to strengthen surveillance programs both for infection in birds, infection in mosquitos, and certainly infection in humans, and to place strong emphasis on the sort of personal measures that people can take to minimize their risk and the risk of their household members for acquiring infection.

QUESTION: Is it fair then to say--

CDC MODERATOR: We're going to limit the questions. Cindy, next question, please.

AT&T MODERATOR: Our next question comes from John Pope, Times Picayune. Please go ahead.

QUESTION: Good morning. This is an open question for Dr. Gerberding or Dr. Hughes. Are there any other epidemiologic trends that you've been able to tease out from the information you've gotten about this year's outbreak, and how it might differ from the previous years?

DR. GERBERDING: I think we've pretty much mentioned what we know so far. The change in the geography, the earlier onset, and possibly some differences in the age of onset. But I stress that that's a possible. We really don't have enough information yet to draw any conclusions about the pattern of how this is affecting adults.

Actually, there are a large team of CDC investigators supporting the intervention programs that are ongoing in Louisiana, and some of the questions those investigators will be looking at include the question you asked--are there any differences in the pattern of the epidemiology this year compared to previous years.

QUESTION: And what are the per capita figures for the states in which you found cases?

DR. GERBERDING: Well, again, we don't have that infrastructure stratified by age yet because we're just--

QUESTION: No; no. Per capita as in cases per.

DR. GERBERDING: I don't have that information.

CDC MODERATOR: John, I think that's something that if you contact the press office, we may be able to run that down for you; but we don't have that right now.

QUESTION: It can take a while to get an answer from your press office. That's why I'm asking you.

CDC MODERATOR: Okay. Well, we can get that information for you, John.

QUESTION: Okay. Thank you.

You've got the case counts by state, though, right?

QUESTION: Yes. When I was at CDC lt year, we put great store by per capita numbers and I was just trying to get those.

CDC MODERATOR: We'll try to get those for you, John.

QUESTION: Thank you.

CDC MODERATOR: Cindy, next question.

AT&T MODERATOR: Our next question is from Anita Manning, USA Today.

QUESTION: Hi. Thank you very much, Dr. Gerberding, and hello everybody.

I have two questions. One of them is about these younger cases. Is there anything--my understanding was that the younger cases also had other health problems, and we've always said with this disease that it's most dangerous for the elderly and people with weakened immune systems.

Is that not correct? With these younger cases, are they healthy young people?

DR. GERBERDING: Let me just say one more time that the early information as was reported by CDC last week, suggesting that there may be earlier age distribution than we've seen in the past is very preliminary, and so the majority of people who have developed encephalitis are older people who have, you know, advanced stage as their major risk factor, and the others, most of the others also have underlying illnesses.

QUESTION: Thank you. And then my second question is about the number. You said it's 34 states. Is that 34 states plus D.C. or including Washington, D.C.?

DR. GERBERDING: It's 34 jurisdictions, plus D.C.

QUESTION: Okay. Thank you very much.

AT&T MODERATOR: Thank you.

Our next question is from Ann Kerns [ph] from Wall Street Journal.

QUESTION: Hi; good morning. Thanks. I have kind of a follow-up question on the issue of the possibly earlier onset that you're seeing. I understand that June is early in terms of West Nile, but I was wondering if it's considered early in this part of the country for other types of mosquito-transmitted encephalitis, like St. Louis, or some of the other kinds that are known to exist there already?

DR. GERBERDING: Jim, do you want to take that question?

DR. HUGHES: Yes. St. Louis encephalitis is not predictable from year to year, but it's not surprising, given that the virus has gotten into the Gulf Coast states, in my opinion, that we're seeing cases earlier in the season.

QUESTION: Okay, and can I ask one other question. I was just wondering if you could tell us a little bit more about ArboNET, what it is, and how it works, and how it's helping in this particular situation.

CDC MODERATOR: Ann, we could probably get you more detailed information if you call us.

Jim, do you want to--

DR. HUGHES: Well, I can just say that ArboNET is one of the many surveillance networks that we have for emerging and reemerging infectious diseases, and it's a network that connects state public health labs with CDC and it's used to share information in a timely fashion in both directions.

QUESTION: Okay. I'll follow up with that later. Thank you very much.

CDC MODERATOR: Next question?

AT&T MODERATOR: Our next question is from the line of John Lehrman [ph], Bloomberg News. Please go ahead.

QUESTION: Hi; it's John Lowerman [ph] from Bloomberg News. Can you hear me?


QUESTION: Great. Okay. I'm wondering what the data on mosquitos, chickens and other monitoring systems you have--what does that say about the velocity of spread in nonhumans, in other states? Particularly I'm wondering about states where we've already seen the virus as opposed to these new states.

DR. GERBERDING: Jim, can you take that question. I had just a little bit of break in my hearing, so I didn't catch it.

DR. HUGHES: Okay. I think it's really too early to say in terms of, you know, trends in individual states. If we're looking at the map to indicate where infected birds have been found, where infected mosquito pools have been found, where infected horses are found, and where humans are found, it's a little bit early in the season to be able to make any comments in terms of the temporal sequences here. It gets quite complicated. This will be certainly a focus of a lot of the data analysis as the season goes on.

QUESTION: So you haven't seen any increases over previous years?

DR. HUGHES: Increases in...?

QUESTION: In infected birds, infected horses.

DR. HUGHES: Well, I don't have the counts of the individual bird and horse findings from previous years in front of me; but suffice it to say with--you know, we've got a number of new states involved for the first time this year. So things are evolving.


CDC MODERATOR: Next question, please.

AT&T MODERATOR: Our next question is from Cathy Kirk [ph], NBC 33, Fort Wayne, Indiana.

QUESTION: Thank you.

I was wondering about, in Indiana we have had no human cases of the virus, mainly out of mosquito pools and dead birds.

Now the local health officials have been spraying the area. My question is, this spraying that they're doing, the public is worried about it being harmful to them because there's so much going on, because we found so many, like the mosquito pools and dead birds all over our city.

So I'm just curious about the spraying, the preventative tactic, locally, that they're using. Can anybody respond to that.

DR. GERBERDING: Well, I don't know specifically about the spraying program in your jurisdiction, but, in general, the way to combat the mosquito population involves either treating water with chemicals that destroy the larvae of the insects, or spraying chemicals that are effective against the adults, and often both measures are used simultaneously or in sequence.

The experience so far in the states where these programs have been going on now for several years suggest that there are very, very few, if any, serious health consequences with either of those approaches, and that, in general, the safety and tolerance to the chemicals is excellent in the population, and basically that they're safe, and certainly the risks that are present, if any, are outweighed by the benefits of dealing with the mosquito population.

The chemicals that are most commonly used come in two major categories, and without really knowing what's involved in the program in Indiana, I couldn't really say any more about what we know about them.

QUESTION: Okay; thank you.

CDC MODERATOR: Next question, please.

AT&T MODERATOR: Our next question is from Amelia Escari [ph], Detroit Free Press. Please go ahead.

QUESTION: Hello, and thank you very much.

I was wondering if it's fair to say, given the spread of the disease so far in the season, that we might see up to twice as many people infected before the end of the season this year?

DR. GERBERDING: You know, what you said at the beginning is the answer to your question. It's too early in the season to really make those kinds of predictions or projections about where we're going to go from here.

In addition to the extent to which we can get adequate control over the mosquito population, the weather, the rainfall, the migration of the birds involved, and many, many other factors, are going to influence how this affects the human population, and probably the biggest factor of all is whether or not people can really follow the precautions that we've recommended, including using the insecticide and doing the common sense things they can do to avoid insect bites.

So it would be really impossible to predict the pattern of the epidemic.

DR. HUGHES: These questions really highlight, again, to me, the importance of continued surveillance at the local level and the need for continuing close interaction between clinicians involved in caring for patients and local and state public health officials.

I don't think we can emphasize that strongly enough.

QUESTION: And further, I'm wondering if there is some threshold number of infected birds or infected animals in a given area, that would predict for you that the virus would likely pass to humans in that area?

DR. GERBERDING: So far we have not been able to identify a threshold effect, and in part that's because we don't have a direct dose response relationship and in part because our capacity to detect the infection in birds and insects is somewhat subject to sampling bias. So the more birds we are able to locate and test, and the more mosquitos that are pooled and tested, you know, the more documented foci we have in a particular community. But that doesn't necessarily reflect the true density of exposure in a specific area.

CDC MODERATOR: Next question, please.

AT&T MODERATOR: Our next question comes from John Pope, Times Picayune.

QUESTION: This is a wonderfully helpful session. I just have two housekeeping questions because I am down in the thick of it here in New Orleans.

How often will we have these briefings and how often can we expect case updates?

CDC MODERATOR: John, I think that's something we're still deciding. I think we'll definitely be going to these more than once a week. We can assure you of that.


CDC MODERATOR: We'll be doing these daily or not, we haven't decided.

QUESTION: Okay; thank you.

AT&T MODERATOR: Thank you, and we go to Seth Bornstein of Knight-Ridder. Please go ahead.

QUESTION: Thanks again.

Dr. Gerberding, you were talking about how this is something we're just gonna have to live with in the future because it is now well-entrenched.

If you take a step back from the current outbreak, in terms of long range, how many cases do you see eventually?

Is there sort of a level, once we're sort of, in the future, all exposed? Do you see sort of a level of how many deaths or cases we'd see a year, once this goes throughout the whole country?

DR. GERBERDING: I wish we had an answer to your question, but, truthfully, it's just not possible to predict or to project into the future how this will evolve, and, again, the biggest factor that will determine the extent to which we see more cases, or fewer cases, is how well people are able to accommodate to the protection measures, and how successful mosquito eradication programs can--or mosquito reduction programs, I should say, will be over time.

QUESTION: Just to follow up. What I'm trying to do is put this in perspective for people.

If this is going to be sort of a common summer thing for us across the nation as it gets hotter, and more mosquito prone for much of the nation, are we looking at putting--I mean, obviously, it's nowhere near the amount of deaths we normally see from flu, but I mean where, in the long range, does this rank in terms of other health diseases? I mean, so as we don't alarm people too much or not too--too little.

DR. GERBERDING: What we can say from looking at the experience over the past three years in the areas of the country where there clearly have been human cases and a lot of infected birds and mosquitos, the number of people affected has not been nearly the kind of scope and magnitude we would associate with something like influenza, which is also a very seasonal illness of course.

So I think there's room for optimism here, that the kinds of control programs that we recommend do have a very favorable impact, and that this is a problem that can be managed without evolving into much larger proportions.

But that does depend on the things that I mentioned earlier, and some of them are not necessarily completely controllable, like the weather.

DR. HUGHES: This experience is a reminder that we have become somewhat complacent in this country about mosquito-borne disease, and we will not be able to remain complacent in order to deal with this problem. As Dr. Gerberding said earlier, we've rebuilt the diagnostic capacity for mosquito-borne viral diseases in states' public health laboratories around the country, but there is more work to be done, and people really should care about the capacity of their local and state health departments to deal with these issues and vector-borne disease specifically.

CDC MODERATOR: Next question, Cindy.

AT&T MODERATOR: Ladies and gentlemen, if you wish to ask a question at this time please press the one. We do have a follow-up from John Pope. Would you like to take that one?

CDC MODERATOR: Yes. This will be the last question we take then.

AT&T MODERATOR: All right. We do have two others on line.

CDC MODERATOR: All right. Yes. Go ahead, John; real quick.

QUESTION: Okay. This may fall into the category of stuff you can't predict yet and we shouldn't let down our guard, but based on previous years, is there any way to tell when people can stop being so scrupulously intent about mosquito, defensive measures regarding mosquitos ? Is there a season for this disease, in other words?

DR. GERBERDING: Jim, I'll let you take that one cause I think you kind of said it before.

DR. HUGHES: I think we're still learning about seasonality in different areas. It won't be the same in all areas. In more northerly climates, obviously, the transmission season will be shorter than in the south, and so, again, it will hang on surveillance data that's collected in different geographic areas from birds, mosquitos and humans.

I think give years from now, we'll be able to have much clearer answers to these questions.

CDC MODERATOR: Next question, Cindy.

AT&T MODERATOR: We have Sharon Collins from CNN Headline News. Please go ahead.

QUESTION: I have kind of a two-part question. What other mosquito-borne diseases might you be concerned about in the future? And I say that in relation to all of the climate change reports that I've read which seem to indicate that we'll not only see warmer weather but the seasons will perhaps last year around, and in that possibility, in that forecast, could this be a more serious problem than it is today?

DR. GERBERDING: Jim made the point earlier about complacency and mosquito control, and I think that, you know, as geographic and weather patterns evolve over time, certainly those factors could make this problem worse.

They could also interact to make it better. We just don't know.

DR. HUGHES: I could add that I think most of you are aware, but you should remember that in this country today, we have mosquitos that are perfectly capable of transmitting malaria, of transmitting dengue, and of transmitting yellow fever.

CDC MODERATOR: Okay. We'll take one more question, Cindy.

QUESTION: Thank you.

AT&T MODERATOR: Our next question is from the line of Isola Pegeurro [ph], Telemundo Network.

QUESTION: Yes; good afternoon. I just came in the conference. I'm putting together, a story together for today's newscast, and my question is how many states have we accounted for as of now in the United States, that are going through the West Nile virus [inaudible]. Louisiana has been testing. Any other states as of now?

DR. GERBERDING: Right now, we have human West Nile infection with disease in Louisiana, Texas, and Mississippi.

QUESTION: Texas and Mississippi. And what would be the best advice that you [inaudible] New York where the virus was first detected here. What are the concerns or things that people should be aware of as of now? Any general advice for the nation, in general?

DR. GERBERDING: Well, the main advice that we're giving to the public is to examine their property and make sure that they have eliminated sources of standing water, to try to cover their skin to the extent possible when they're outdoors, and to use an insect repellent when they're outdoors.

QUESTION: Great. Thank you very much.

CDC MODERATOR: Okay, Cindy, I think that's it. I want to thank everybody once again on behalf of Dr. Gerberding and Dr. Hughes for participating in this telebriefing, and once again I'd like to just go over the phone numbers for our public inquiry hotline that Dr. Gerberding shared with everyone earlier.

The English number is 1-888-246-2675. The Spanish hotline is 1-888-246-2857, and we have a hotline for the hearing-impaired, 1-866-874-2646. So thank you once again.

AT&T MODERATOR: Ladies and gentlemen, that does conclude our conference for today.

Listen to the telebriefing

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