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, 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
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
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
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
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
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
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
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
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
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
So the bottom line is most people are still susceptible to getting
infected and need to be vigilant and protect themselves against mosquito
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
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?
DR. ZIELINSKI-GUTIERREZ: Yeah.
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
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
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
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
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
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
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
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
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
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
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 www.cdc.gov/westnile.
The EPA press office is aware of this call today and if you need to reach
them, the phone number is  564-4355, and if you have any further
questions for CDC, give us a call at  639-3286. Thank you, everyone.
MODERATOR: That concludes today's conference.
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