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Telebriefing Transcript
CDC Adopts New Repellent Guidelines for
Upcoming Mosquito Season

April 28, 2005

MS. MORCONE: Thank you very much and thank you, everyone, for joining us today.

Today, CDC, in addition to hosting this telebriefing, will issue a news release, so look for that in your mailboxes shortly. We're adopting new West Nile Virus repellent guidance for the upcoming mosquito season.

I am pleased to introduce Dr. Lyle Petersen, director of our division of vector-borne infectious diseases, and Dr. Emily Zielinski-Gutierrez, who's a behavioral scientist in that division, who will talk about the recommendations, our prevention messages and key facts about West Nile Virus itself.

Dr. Petersen, please go ahead.

DR. PETERSEN: Thank you, Jennifer. Good morning. As all of you know who have been covering West Nile Virus for the last couple of years, that mosquito season is now rapidly coming, if not already here, and with it, West Nile Virus.

This morning we'd like to emphasize that Americans now have more options than ever to use in protecting themselves from mosquito bites, which remains a mainstay of protection against West Nile Virus and other mosquito-borne diseases. Today, the CDC is releasing new guidance about effective mosquito repellents now available in the United States. This updated guidance includes addition of two active ingredients, the Picaridin and oil of lemon eucalyptus, which have been shown to offer long-lasting protection against mosquito bites.

Repellents containing DEET, may I emphasize, these repellents containing DEET continue to be a highly effective repellent option and are also included in the CDC guidelines.

DEET, actually, we have the most experience with over the years and it's been shown to be an extremely safe and effective repellent and remains a very important option for consumers.

Picaridin, which is one of the ones we're now adding to our list of recommendations as far as effective repellents, is also known as KBR 3023, and this is an active ingredient that has been available in Europe, Australia, Latin America and Asia for some time.

Evidence indicates that it works very well, often comparable with DEET, and with Picaridin there's been, as I emphasize, there's been a long-standing experience in other parts of the world which have shown it to be safe and effective.

One product containing 7 percent Picaridin is being distributed in the U.S. this year, and I'm confident that other products containing Picaridin will be on the market also shortly.

The other ingredient that we're adding to our list of recommendations is oil of lemon eucalyptus, also known as P-menthane diol, or PMD, for short. PMD is a plant-based repellent that gave protection time similar to low concentrations of DEET products in two recent studies, and is available in a variety of formulations throughout the United States.

Now I must emphasize that oil of lemon eucalyptus, although it appears to have a efficacy similar to low concentrations of DEET, the experience with oil of lemon eucalyptus is less than the many years of experience that we've had with DEET over the years, but it does appear to be a good alternative to DEET.

Now I'd like to just mention a few things about the upcoming West Nile Virus season as I'm often asked, What's going to happen this year?

West Nile Virus has reached from coast to coast and last year was present in 47 of the 48 continental states in the U.S. and what we've observed over the last years is that once West Nile Virus has entered a state, it's stayed there, it doesn't disappear. So this is something that we're going to have to learn to live with over the upcoming years.

What it's very difficult to do is to predict how much West Nile Virus activity will occur in a given place in a given time, and therefore throughout the United States we must be vigilant and be prepared for a West Nile Virus epidemic occurring in a place where it has been before or in potentially new places as well.

I expect to see continued, if not increasing West Nile Virus activity in the western part of the United States as late last year West Nile Virus entered new areas of California and Oregon, and I expect that continued transmission and expansion of the virus into the Northwest to occur.

As far as the rest of the country, as I mentioned earlier, it's difficult to determine how much West Nile Virus activity will occur, because, for example, West Nile Virus activity is dependent on such factors as weather, which is difficult to predict months in advance.

However, as I emphasize, we must be prepared, and I think the new addition of these additional repellents will help prepare people to prevent mosquito bites this summer.

That is what I'd like to say this morning. I would like to turn it over to Emily Zielinski-Gutierrez, who can maybe fill you in a little bit on some of her data about the use of repellents in the United States and some studies that have been done in the last couple of years.

DR. ZIELINSKI-GUTIERREZ: Thanks very much, Lyle.

Nationwide, about 40 percent of people report that they use mosquito repellents with any regularity, and that's data from just last, a survey in October-November.

Use in the Pacific region was even lower. It was only about 23 percent of people in the states of California, Oregon and Washington, citing that they used any mosquito repellent regularly, and that's even during last West Nile Virus season. So what's clear from that is that there are a great many people who are unprotected from mosquito bites, that could very well be carrying West Nile Virus.

This change in our information is simply to help people interpret what they're going to find when they go to the shelves in their stores nationwide, and the key is really that people remember to use a repellent in the first place, and then to apply it, according to label instructions when they start getting--to reapply it when they start getting bitten, really, no matter which of these repellents that they're choosing.

Our hope is that in providing some additional information about the things that people are going to find when they go to the store will remind folks to use repellents and to make them a regular part of outdoor activities during warm weather. It really only takes a few seconds to put on a repellent and doing so can reduce your risk of becoming infected with West Nile Virus.

It's hard to think that something as small as a mosquito can alter your life, but, really, West Nile Virus can be a terrible disease and it's worthwhile to take those few seconds to do something to avoid becoming infected.

Notably, people over 50 have significantly lower rates of repellent use than younger people, and we found that in our research, research done by Harvard University as well. But people over 50 are at a higher risk for getting severely ill if they become infected with the virus.

So I would challenge adults to remind each other to use repellent. We often focus on worrying about infection in children, which is much less of an issue with West Nile Virus, and in fact it is the mature adults who are at higher risk.

So I would say that people can make it easier on themselves, have repellent at the picnic table, near the back door with, you know, gardening or golfing supplies, for instance.

And in some of our studies, talking with people in areas that have large Latino populations, and also from survey data, we've been able to see that there are notably lower rates of repellent use among Latinos as well, and so certainly if we're looking at areas that were affected last year, like Arizona and California, that do have large Latino populations, this means that there's a particular challenge to make information and products accessible and available to Latino audiences.

Some of the other things that people can do to prepare for this session: watch for mosquito breeding sites that may, places that may have standing water, around your yard, around your house, and to certainly find out if your community has a mosquito control program and insect repellent--I'm sorry--an insect control program, and if it doesn't, really work with the local officials to mobilize and find ways to approach community control from a larger communitywide perspective.

I think that's the end of my remarks for the moment, Jennifer.

MS. MORCONE: Great. Thank you both very much and we're ready for questions. Sara, we're ready for questions.

OPERATOR: Thank you. We will now begin the question-and-answer session. If you'd like to ask a question, please press star one. You will be prompted to record your name. To withdraw your request, press star two. One moment, please, for the first question.

Miriam Falco with CNN, your line is open.

QUESTION: Hi. Thanks for taking the call. Two questions. Number one, any side effects, any concerns people, especially moms might have about these new things that should be in your repellent? And what have we learned over the several years now that we've had West Nile Virus in this country about people who've already been exposed to it? Anything in terms of how resilient folks in states where it's been several years now have become to? Any details on that?

DR. PETERSEN: Thank you, Miriam. This is Lyle Petersen. Your concern is about side effects, your question about side effects or concern. One thing I would like to emphasize is that these products are all EPA-labeled products, and so the EPA has determined that they are safe to use on humans, and we are relying on EPA to make an effective determination about that.

Oil of lemon eucalyptus is not currently recommended for children under three years of age, it's not labeled for that, and the best thing that people can do is to follow the instructions on the label of the bottle, and if they do that, there should be no safety concern.

Now what we've already learned about people already exposed. Right now, we estimate that about a million people in the United States have been infected with West Nile Virus. That means the vast majority of people are still susceptible to infection and even in places where we've had substantial outbreaks, less than 5 percent of the population has been exposed to the virus.

So the bottom line is most people are still susceptible to getting infected and need to be vigilant and protect themselves against mosquito bites.

For people who have already been infected, we believe that an infection with West Nile Virus will confer lifelong immunity.

MS. MORCONE: Thank you, Lyle. Next question, please.

OPERATOR: Todd Zwillich, WebMD News, your line is open.

QUESTION: Hi. West Nile Virus in 48--47 of 48 states. So which state is the lucky one so far?

DR. PETERSEN: Washington State.

QUESTION: I beg your pardon?

DR. PETERSEN: Washington State.

QUESTION: Oh. Washington State. But you also said, Dr. Petersen, that you expect, because it's now in Oregon and parts of California, it's essentially a matter of time before Washington State is affected as well?

DR. PETERSEN: That is correct.

QUESTION: And would you expect it this year or is that unpredictable?

DR. PETERSEN: Well, it's hard to make predictions but it would not surprise me to find it in Washington State this year. Given the speed that the virus has spread across the country, it's virtually on Washington State's border at this point, and so it would not be surprising, at all, to find West Nile Virus activity in Washington State this upcoming year, but I can't say that with absolutely certainty.

QUESTION: Have there been any reported cases north of the border, in British Columbia, or any of those regions? Or does it not range that far?

DR. PETERSEN: There have been no reported cases in British Columbia. There have been reported cases in Alberta.

QUESTION: Okay; thank you.

MS. MORCONE: Next question, please.

OPERATOR: David Wahlberg, Atlanta Journal-Constitution, your line is open.

QUESTION: Hello; thank you. I've got two questions. The first one is you mentioned that there's one product being distributed this year in the U.S. Can you verify that that's the Cutter Advance repellent? And why, if this chemical was available in repellent in other countries for so long, why did it take so long to appear in the U.S.? That's all my first question.

And my second question is why not soybean oil? There's been some talk about that too.

DR. ZIELINSKI-GUTIERREZ: This is Emily Zielinski. I can field that question for you. Yes, the product that we're referring to is in fact Cutter Advance.

DR. PETERSEN: Or Picaridin.

DR. ZIELINSKI-GUTIERREZ: Or Picaridin. And the reason that it was not approved in the U.S. previously is essentially that the active ingredient had been gone through registration with EPA a number of years ago but simply none of the commercial interests had brought it to market, probably because many consumers were satisfied with DEET, and now with greater attention to mosquito repellent, which is certainly good news to us, and more consumers interested in using mosquito repellent, the commercial interests just felt like it was a good time to bring that.

So I think that is really the answer to that question.

And your other question was about the soybean oil, and one product with soybean oil has tested well in several studies but I would note that they haven't gone through EPA registration as a mosquito repellent because there is a status of being exempt as a foodgrade product, though some products that are foodgrade can also choose to go that extra step with EPA with registration as a biopesticide.

So given that it's really EPA's mandate to review products for safety and efficacy, we defer to their judgment and those products that have chosen to pursue registration with them.

MS. MORCONE: Thank you, Emily. Next question, please.

OPERATOR: John Lauerman, Bloomberg News, your line is open.

QUESTION: I was wondering, can you tell me who makes the other products, the ones that are available in Europe right now. Do you know which company makes them or what the names of the products are?

DR. ZIELINSKI-GUTIERREZ: It's often sold as Autan, A-u-t-a-n, in other countries, pretty widely, both Europe and parts of Asia, to my knowledge.

QUESTION: That's Autan?

DR. ZIELINSKI-GUTIERREZ: The product name also sometimes goes by Bayrepel, the actual active ingredient.

QUESTION: Okay. So it's Autan and Bayrepel?


QUESTION: Any idea who makes it?

DR. ZIELINSKI-GUTIERREZ: I believe that the active ingredient is a Bayer product but it's licensed to different commercial interests in different countries.

QUESTION: Okay; thanks very much.

MS. MORCONE: Next question.

OPERATOR: Mandy Gardner, Health Day, your line is open.

QUESTION: Yes. You had mentioned before that one of the ingredients wasn't suitable for children under the age of three. I'm wondering if there are any other ways to distinguish which product would be good for what type of person in terms of both efficacy and safety?

DR. PETERSEN: Yeah. First, just to correct you a little bit, "not suitable for children." It's not approved for children under three. That doesn't mean it's dangerous or anything. It just hasn't been sufficiently tested in young children. And the best thing the consumer can do is look on the label because the label will give the approved usage.

MS. MORCONE: Thanks. Next question, please.

OPERATOR: Richard Knox, National Public Radio, your line is open.

QUESTION: Yes; thanks. A couple of things. One is are there any advantages to this new ingredients? Will some people, is it thought, will some people prefer one of these new ingredients to DEET, and if so, why so? I have a second kind of question but maybe we should do that one first.

DR. ZIELINSKI-GUTIERREZ: Sure. This is Emily. I'll take that question. There are some essentially cosmetic differences among the different repellents, and consumers I think will just have to try them out and see which ones they prefer. I'm sure the manufacturers will be more than happy to tell you their, you know, the relative merits. We're really focusing on the efficacy issues.

There are always people who say that they prefer a plant-based repellent, and that's really why we made the effort to evaluate the literature that was available on the biopesticide such as the oil of lemon eucalyptus.

So in terms of efficacy, these are equivalent at the lower range now, because the Picaridin's only at 7 percent, and the oil of lemon eucalyptus at about 30 percent equals a low concentration DEET product. People are also going to have to take into consideration how long they're going to be outdoors, and either reapply any one of these repellents, you know, when they start getting bitten, or choose one of the DEET repellents that's available in a higher concentration if they're going to be outdoors for, you know, six or more hours, for example.

I mean, the message is always people have to take responsibility and use something they're going to reapply as needed, and if you start getting bitten, you know, go ahead and put more repellent on.

QUESTION: Maybe I could just follow up on that by asking without having you do the marketing for the companies, in behavioral terms, would you expect, or are you hoping, anyway, that having these new alternatives will increase compliance with your advice?

DR. ZIELINSKI-GUTIERREZ: Yeah; absolutely. We're hoping that by consumers having more options available and not feeling that they just have sort of one category of products that they can use, that they'll find something that they really feel more comfortable using, either because they like the smell of it better, they like the feel of it better, or it's just, you know, more comfortable for them to use.

So we see this as an advantage in the fact that people have just a wider array of choices.

QUESTION: And if I'm allowed, my other question had to do with just getting an update from, I guess Dr. Petersen, about the West Nile numbers. How many cases did we see last season? What sort of mortality did we see? Do we know anything about long-term effects of people who had West Nile and recovered? And what about organ transplants and that problem?

DR. PETERSEN: Okay. Let me start out with--your question's multiple. How many cases did we see last year? I will get that number for you in a second. I actually do not have it in front of me; but I will get that to you.

The second question about long-term effects. We know that with people who get the more severe manifestations of West Nile Virus, particularly the encephalitis syndrome, that a fairly high percentage of them will have some kind of long-term sequelae, and many of them do not report to their previous level of living. In other words, many cannot return back to work because of various neurological problems.

We are currently in the process of studying the long-term effects of West Nile Virus, which is hard to do because the virus has only been here for a few years. So we don't have years and years of experience. But we're in the process of trying to evaluate the long-term effects.

We have been looking, in particular, at people who have the paralysis syndrome and what we found with people with the paralysis syndrome, that complete recovery from the paralysis syndrome is uncommon. It can occur but it's less common.

It's similar to what occurred with the poliomyelitis outbreaks years ago, with the polio virus.

I do have the numbers for you from last year. We had 900 cases of persons with, reported with severe neurological disease, meaning meningitis, encephalitis, or acute flaccid paralysis.

We had 1,017 people reported with West Nile fever, [Editor’s note: 553 people with unspecified/other clinical manifestations] for a total of 2,470 total. There were 88 fatal cases or 88 fatalities reported to us.

I would emphasize that we know that there's a considerable underreporting among people with West Nile fever, because many people have milder symptoms and don't go to the doctor or it's not diagnosed, and the true number of cases with West Nile fever is undoubtedly substantially higher.

There was a third part of your question, I think, something with effects?

QUESTION: Yeah; thank you. About organ transplants. What can be said about that?

DR. PETERSEN: Yes; thank you for reminding me. The data--we know for a fact that West Nile Virus is particularly severe in people who've had previous organ transplantation, probably due to the immunosuppressives that they take to prevent rejection of their organ, and some studies in Canada indicated that among people with organ transplantation, once they get infected with the virus, about 40 percent of those people will develop severe neurological disease.

That contrasts with less than one percent in the population at large. So people with organ transplantation are at extremely high risk for severe disease, if they're exposed to the virus, and need to be especially vigilant to protect themselves from West Nile Virus.

MS. MORCONE: Thanks. Next question, please.

OPERATOR: Jim Erickson, the Rocky Mountain Newspaper, your line is open.

QUESTION: Hi. This is for Emily and it's a follow-up on a previous question. Did you in your research find that some people were reluctant to use DEET because of lingering safety concerns, if unfounded, and are you hoping to convince some of those people to try these new products, in part, because they may appear to be safer or innocuous, whereas there is, at least among some people, a feeling that DEET is unsafe?

DR. ZIELINSKI-GUTIERREZ: Yeah; thanks, Jim, that's a good question. And definitely there are people out there who, for whatever reason, when we go out and talk to people, we find a lot of just sort of lingering uncertainty about DEET.

And, you know, as you mentioned, it's often very unfounded, but the fact is, you know, very few people pay as much attention to mosquito repellents as we do, and so, you know, they get to the grocery store and just need to make a determination about what they want to pull off the shelf.

And so we are hoping that those people who are just, you know, solidly not comfortable using DEET will find that one of these other products is, you know, is more to their liking, and, you know, that's emphasizing that those concerns DEET aren't based on data but certainly we've tried everything to convince people that it's a, you know, a completely reasonable product to use.

But if there are more options out there, yeah, we're definitely hoping to convert those nonusers into people who do use repellent.


MS. MORCONE: Next question, please.

OPERATOR: Kevin Darst, Fort Collins Coloradan, your line is open.

QUESTION: Yes; thank you. I have a question about the community programs you talked about earlier. It seems like in northern Colorado, this year, a lot of cities, governments, whatever, have abandoned especially spraying programs, and are going instead with sort of smaller-scale larvacide.

I guess I'm curious to know what you think about that trend, and also behaviorally, do we know if people are more or less inclined to use repellents if they know that their community has such a program?

DR. ZIELINSKI-GUTIERREZ: I'll answer your question about the repellent first and then turn over to Lyle for the question about larvaciding.

That definitely people make decisions to, you know, actually remember to--or they're motivated to pick up and use a repellent on their way out the door, if they're aware that there's West Nile Virus in their community and that just emphasizes the importance of all the surveillance or disease-monitoring activities that are going on -- the collection of birds, the reporting of people in their community with illness. And what we hope that people are proactive and, you know, preparing for the season and using repellent, we also want people to be smart and to, you know, respond to the data.

That's part of what makes surveillance worthwhile, so people can make informed decisions about, yeah, the risk is higher, I should go ahead and use repellent. We definitely see people reacting to that, you know, that perception that yeah, risk is higher, I better do something.

DR. PETERSEN: Yeah, and as far as your question about mosquito control, West Nile Virus is actually very cruel from a public health standpoint because what--I explained earlier, that West Nile Virus is a episodic disease and in a given area you can have a huge outbreak one year followed by moderate or even no activity the following year, and one or more years may go by with relatively low activity and then there's another outbreak.

And I think it's human nature to respond to a crisis and once an outbreak happens, then everybody's vigilant and mosquito control programs are well-funded, and then nothing happens for a couple years and then we let down our guard and then there's another outbreak.

So my point is that mosquito control programs need to be in place over the long run because it's a very unpredictable illness.

Now as far as larvaciding or spraying goes, the one thing that I would like to emphasize is that you can imagine that across the United States there's a wide variety of ecologies. You go from desert climates all the way to forest climates and to tropical climates, and what works in one area, or may be appropriate in one area may not be appropriate in another area.

For example, in Phoenix, Arizona, where they had an outbreak last year, abandoned swimming pools were a huge problem. Well, that's not a problem in New England, for example. So the strategy is very location-dependent.

Now as far as larvaciding or spraying, you have to differentiate what is done prophylactically versus what is done during an outbreak.

Prophylactically is to get rid of mosquito breeding habitat, to put larvicides down, to prevent mosquitoes from breeding in aquatic habitat, so to kind a knock down the mosquitoes when they're still in the aquatic stage, where they're much easier to get rid of.

Later on in the season, if an outbreak does occur where there's a lot of human cases occur, that's when the aerial spraying and other activities go on, where you're trying to kill adult mosquitoes.

That strategy is a very short-lived strategy but it's effective in the case of a crisis and that's what most people think about mosquito control. They see, you know, the spray trucks going by.

But, really, the name of the game is to be vigilant, keep the larviciding, keep down the, early in the season, to try and knock down those mosquito populations early before it becomes a problem.

Also trying to get rid of the mosquito breeding habitat. And having lived here in Fort Collins with you, those activities are definitely going on and quite effectively.

MS. MORCONE: Great; thank you.

QUESTION: Thank you.

MS. MORCONE: Do we have any more questions?

MODERATOR: Elaine Aradillas, Orlando Sentinel, your line is open.

QUESTION: Hi. I just had a quick question about the statistics on Latinos. You said that Latinos are less likely to use repellent and I was wondering if you had any idea what causes that or reasoning for that?

DR. ZIELINSKI-GUTIERREZ: Yeah; sure; that's a great question, Elaine. We have done some, a number of focus groups in different areas along the border, as well as here in Colorado with Latinos and some of the different issues that can come up, if people are more recent immigrants, part of the issue may be that repellents simply aren't an affordable option in a lot of Latin America and so people don't grow up being accustomed to using them.

And another issue may be that, especially among people who primarily speak Spanish, the marketing hasn't always targeted Latinos as much, and also some of the names used for products in this country were not necessarily familiar because the Picaridin products have been available under completely different names in Mexico for a long time, for instance.

So a lot of it just has to do with background, what did people grow up using, you know, what's their default activity to get rid of mosquitoes, and so we're hoping to be able to change some of that through, you know, Spanish language targeted materials.

QUESTION: Okay; thanks.

MS. MORCONE: Great. Any further questions?

MODERATOR: Our final question, David Wahlberg, Atlanta Journal-Constitution, your line is open.

QUESTION: Thank you so much. I just had a quick follow-up question for Emily.

When was Picaridin registered as an EPA product for mosquito repellent?

DR. ZIELINSKI-GUTIERREZ: David, I have to admit that I'm not exactly sure what year it was--that the active ingredient itself was first registered. I want to say it was at least three years ago but I would recommend that you check with EPA for specific information on that.

The registration of--just to clarify, the companies have to register the active ingredient and then the individual products have to be registered as well.

And so this Cutter Advance product that we're looking at on the market now, I believe got its registration approved some time in December of 2004.

QUESTION: Thank you very much.

MS. MORCONE: Great. Thank you all for joining us today. We really appreciate it. As always, you can find a host of West Nile materials on our Web site at The EPA press office is aware of this call today and if you need to reach them, the phone number is [202] 564-4355, and if you have any further questions for CDC, give us a call at [404] 639-3286. Thank you, everyone.

MODERATOR: That concludes today's conference.

Additional materials:

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