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CDC Telebriefing Transcript
West Nile Virus in the United States
August 14, 2003
CDC MODERATOR: Welcome, everyone, and thanks very much for joining us.
Today, we are going to provide a West Nile Virus update and discuss an article in this week's MMWR, "Detection of West Nile Virus in Blood
Donations in the United States in the United States in 2003."
Joining us on-line are Dr. Stephen Ostroff, spelled S-t-e-p-h-e-n O-s-t-r-o-f-f, deputy director of the CDC's National Center for Infectious
Diseases, Dr. Tony Marfin, spelled T-o-n-y M-a-r-f-i-n, acting deputy director of the CDC's of CDC's Division of Vector-Borne Infectious Diseases;
and Dr. Hira Nakhasi from the FDA's Division of Emerging--I'm sorry--Director of the Division of Emerging Transfusion-Transmitted Diseases and the
Center for Biologics Evaluation and Research.
Dr. Ostroff will open the discussion with the West Nile Virus update and then followed by Dr. Marfin and Dr. Nakhasi, who will discuss highlights
of the article, briefly, before we open up the conversation for questions.
DR. OSTROFF: Thanks very much, Dave.
We appreciate the ongoing reporting of the West Nile situation. As we had anticipated, West Nile is currently really picking up momentum within
the United States. It's important to point out that based on prior seasons, we are just now getting into the peak period of West Nile activity
which, over the last several years, has been in late August and early September, and it certainly looks like we will be following a similar course
over the next several weeks.
Currently, we are reporting a total of 393 human cases of West Nile Virus infection within the United States. This represents a tripling of the
number of cases that we had reported only a week ago, and so of that 393 human cases, 240 of them have been identified and reported to us in the
Arbonet system over the past week.
About 50 percent of these cases are being reported from the State of Colorado, and the next-highest number is from the State of South Dakota,
followed by the State of Texas. As opposed to what was seen last season, where a lot of the earliest activity was in the Mississippi, Lower
Mississippi River drainage area, a great deal of the West Nile activity that we are currently seeing is in the high plains and in the Rocky
As of today, which was reported in the MMWR, there have been 42 states that have reported any West Nile activity, and information that is not
contained in today's MMWR, but was just reported officially to us this morning, the first recognition of any West Nile activity was reported in
the State of Arizona, which identified a single mosquito pool that was West Nile positive. This represents expected continued expansion of West
Nile into the far areas of the Western United States, and certainly would be a trend that we would continue to see over the next month or two.
In terms of recommendations for the public, as was stated by Dr. Gerberding last week, now is really the time to step up one's prevention
activities, whether it's taking measures to reduce sources of mosquitoes around the home or, in particular, taking personal protective measures to
reduce your risk of being bitten by mosquitoes when engaged in outdoor activities. This involves personal protective measures, such as use of
insect repellents, as well as wearing light, long sleeves and long pants, and also doing what can be done around the home to reduce sources of
standing water in order to reduce the likelihood of mosquito breeding.
The main purpose of today's telebriefing is to discuss one of the major changes that has occurred between last year and this year, which is in
recognition of the problems that occurred last year with transfusions, is the screening of the blood supply. And there is an extensive article in
this weeks' MMWR, describing the current efforts to screen and protect the blood supply and to reduce the likelihood of transfusion-associated
transmission of West Nile Virus.
And to discuss that further, I will turn it over to Dr. Tony Marfin to discuss the contents of that article.
DR. MARFIN: Thank you, Dr. Ostroff.
During the peak of the 2002 West Nile Virus epidemic, transfusion-associated transmission was documented for the first time ever.
Last year, 23 persons who received transfusions who became ill were identified during the subsequent investigations. Since that time, because many
have anticipated a repeat of the 2002 epidemic, the blood banking industry, the FDA and several biotech industries have worked to develop and
implement assays that can detect West Nile Virus in donated blood.
As of July the 14th of 2003, all civilian blood donations collected in the United States, including Puerto Rico, have been screened using assays
based on finding West Nile Virus' genetic material.
To assist with national surveillance efforts, the blood collection agencies have shared their screening data with state health departments and
with the Centers for Disease Control and Prevention.
Of the nearly 1,100,000 screened donations from mid-July to early August of this year, approximately 160 donations were found to be repeatedly
reactive using these assays. Almost all of these donors have had no symptoms at all. All of the blood and other components from these donations
have been removed from circulation.
Many of these infected donors have been reported to state health departments, to Arbonet, which, as you know, is CDC's surveillance system for
all mosquito-borne viral diseases. These donors have been reported from Colorado, Florida, Louisiana, Mississippi, New Mexico, South Dakota, and
Texas. There is a great deal of agreement between the list that I just raised to you and the list of states that Dr. Ostroff mentioned in his
State health departments have responded to these reports by increasing disease surveillance and control efforts in the counties of residence of
Although the current technology for blood screening detects most viremic donations, we strongly encourage physicians to report patients who have
received blood transfusions within the four weeks before development of an illness compatible with West Nile infection. These cases should be
immediately reported to state or local public health authorities.
In conclusion, because most West Nile Virus-infected persons remain asymptomatic, collection of data regarding these viremic donors has been an
invaluable surveillance tool, in addition to its intended value of screening and removal of potentially infectious products from the nation's
So, with that, I will turn it over to Dr. Hira Nakhasi.
DR. NAKHASI: Thank you, Tony, and thanks, Dr. Marfin, Dr. Ostroff.
I just wanted to, first of all, thank CDC and others for having FDA the opportunity to comment on this MMWR article and to highlight some of the
information which is provided in that article.
I just want to up-front state that there has been a tremendous amount of cooperation between CDC, FDA, blood establishments, test kit
manufacturers in the development of this test which is now being used as an investigational test to screen blood, as Dr. Marfin suggested.
This whole process started as of August 2002, when FDA issued an alert to blood establishments to exercise vigilance to exclude potential donors
with flu-like symptoms prior to reports or a demonstration that West Nile could be transmitted by blood.
Following that, subsequently, in October and in May of this year, we issued two guidance documents, basically, telling--to prevent the donors with
symptoms from donating and to manage implicated products.
In addition to that, I would like to thank the test kit manufacturers who really took upon themselves in a short period of nine months, last
year till now, that they developed these investigational tests, which are still in experimental basis. However, as you heard from Dr. Marfin's
presentation, we have already interdicted more than 150 samples which would otherwise have gone and transfused into people and may have caused the
So I think that, again, evaluation of these tests is being done, as of now, and as Dr. Marfin suggested, the blood supply is being tested.
And I would also like to add that in addition to that, the regulatory pathway for these developmental tests includes all donors under IND, linked
product released to the developmental test results. It requires confirmatory testing and unit donor management.
This investigation started this year in mid-June of 2003 and, as you heard just now, already has produced a fruitful--you know, the results of
that study, that we have interdicted many samples.
FDA is also developing reference material and standards which companies can use to validate these tests because they are still under
investigation, and FDA is also working with these IND holders to increase sharing of these positive samples to facilitate test validation and to
ensure that test performs at the same level.
Then, in addition to that, I should give credit to the blood organizations. They had voluntarily over collected some of the fresh frozen plasma in
anticipation of this West Nile activity this year so that there's no, you know, during the wintertime, when there was no West Nile activity, so
that blood sampling products could be used during this time if there is a shortage.
So, in conclusion, I would just like to say that for those individuals who need a blood transfusion, the benefits strongly outweigh the risks, and
I would like to remind potential donors that donating blood carries no risk of acquiring West Nile Virus.
Thank you very much.
CDC MODERATOR: Thank you, Dr. Nakhasi.
This is Dave, and I'm sorry I did not provide the spelling of his name. It's Dr. Hira Nakhasi. He's spelled H-i-r-a N-a-k-h-a-s-i.
And, John, at this time, we're ready to take questions.
OPERATOR: Certainly, and for those on the phone, just a quick reminder, if you do have a question, please press star, then one.
First, we'll go to the line of Michael Lemonick with Time Magazine. Please go ahead.
QUESTION: Thank you.
I had a more general question about West Nile this year. Early in the spring we were told that this was likely to be a much worse season for West
Nile than previous seasons due to heavy rains and so on, and at least up until this week, it looks as though it's about comparable, in terms of
number of deaths and number of cases. Are we still expecting the season to get much worse? If not, why not, and if so, why haven't we seen it?
DR. OSTROFF: Yes, this is Dr. Ostroff. I'll try to take that question.
It's always very, very difficult to predict. I think what most of us had indicated pretty consistently was that there was every reason to believe
that this year's West Nile season could be every bit as severe as the season that we saw last year.
As you know, last year's West Nile epidemic was quite unprecedented in its scope and scale, and I know that there were many of us that were hoping
that it wouldn't be as extensive and as difficult as last year's season was. That was part of the reason to take some of the measures which were
just mentioned, in terms of doing everything that we could to reduce the potential for disease transmission, particularly through the blood
And at least based on what we see at this point, it looks like that we're progressing pretty much at pace with what was seen last year. It's
always difficult to predict what might happen over the next month or so. But, again, if what has happened the last couple of seasons holds true
this year, we would anticipate we're just getting into the peak of transmission over the next several weeks. And so at least by every barometer
and parameter that we can measure, it looks like it's running fairly at pace with what we saw last year.
CDC MODERATOR: Thank you.
John, if we could have another question, please.
OPERATOR: And that's from David Wahlberg with the Atlanta Journal. Please go ahead.
QUESTION: Hi. Yes, I was wondering do we know how many of the 163 people whose blood donations tested positive during screening were symptomatic
or became symptomatic and if any of them are included in the 393 reported cases?
CDC MODERATOR: Dr. Marfin, do you want to take that?
DR. MARFIN: Yes, I will.
Part of the process of following up on the assay, which is a developmental assay, is to follow up with patients and ask them if they have
developed symptoms. So many of the 163, and I would venture to say most of the 163, are in the process of getting follow-up blood samples, as well
as questionnaires, filling out questionnaires with regard to symptoms.
So we do not have a complete number on the 163. We do know that some, and that's probably about as far as I can say, some have developed West Nile
fever. We know that at least one has developed West Nile encephalitis. And, yes, some of those are included in the overall total of cases reported
CDC MODERATOR: Thanks, David.
John, next question, please.
OPERATOR: That's John Lauerman from Bloomberg News. Please go ahead.
QUESTION: Hi. Thanks for taking my question.
In terms of the number of cases that you've seen so far, the number of positive screens that you've seen out of a million donations, is that more
or less in line with what you expected to see? Did you expect to see more or less?
DR. OSTROFF: Again, I think this is for you, Dr. Marfin.
DR. MARFIN: If we look back at last year, we look at 2002, when we had the largest West Nile meningoencephalitis outbreak that ever occurred ever,
we estimated there were probably somewhere between 400 and 500 donors who may have had West Nile virus in their blood. Today we've identified 160.
We estimate that we are approximately a quarter to a third through this year's epidemic. So it is comparable to what we would have suspected.
CDC MODERATOR: Thank you. Thank you, John.
And John, next question, please.
OPERATOR: And that's Jennifer Mitchell, NBC, Chicago. Please go ahead.
QUESTION: Hi. I got in a little bit later on this. I wanted to know if you could repeat what [inaudible]--
CDC MODERATOR: We're having trouble hearing you.
QUESTION: Hi. Is this better?
CDC MODERATOR: Yes, much.
QUESTION: I came in a little bit late after the beginning. Could you please repeat some of the states that you've seen West Nile now migrate too?
And also, can you also talk a little bit more about the screening process for the blood? Is that a test that is now being used across the U.S., or
just in certain states?
DR. OSTROFF: This is Dr. Ostroff. Let me take the first part of your question. And we apologize. We recognize that there's been some problems with
this computer worm that allows--didn't allow everyone to be aware of the fact that we were doing this telebriefing as expeditiously as possible.
As far as new locations for West Nile, at the end of last year there were actually very few states that hadn't recognized West Nile activity in
one way or another, either in equines, in birds, in mosquitoes or in humans. The only states that we had not seen activity last year of the
continental 48 states were the states of Oregon, Nevada, Arizona and Utah. So far this year virtually all locations have once again identified
West Nile activity. The only new state which has reported activity is the state of Arizona, which has recognized a positive mosquito pool.
For the second question, let me turn that over to Dr. Marfin.
DR. MARFIN: Thank you, Steve. I think that the question was asking about the test and whether it's being used in other ways. The tests in the
blood banks are based on finding the genetic material from the West Nile virus, so people actually have to have virus in their blood at the time
of the donation for it to be found, and that is--that's what makes them infectious, because of the fact that they have the virus in the blood. It
is not a test that's based on finding antibody to West Nile virus. By the time people develop antibody they are in fact well on the way to
being--resolving the infection in most cases.
With regard to the testing, it is now being done in all of the blood centers across the country. I think that you are asking if it is a test that
would be used more broadly than the blood banks, and, no, it would not be. In fact, most diagnoses of West Nile virus in this country are made by
detecting antibody, those proteins that are in the blood that actually fight the infection.
That is a much more efficient way of diagnosing infection in the general population.
CDC MODERATOR: Thank you, Jennifer.
John, next question, please.
OPERATOR: And that's Anita Manning with USA Today. Please go ahead.
QUESTION: Hi. I am wondering about the preponderance of cases in Colorado, and I have heard that Colorado is reporting all cases, and that some
states are only reporting the most severe cases. Is that correct?
DR. OSTROFF: Well, let me try to address that and then turn it over to Tony Marfin. Indeed you're correct that if we look at the data that has
been reported to us so far this year, a higher proportion of the cases that are reported are the milder form of West Nile which is West Nile
fever, than have been reported in previous years. Last season about a quarter to a third of all of the case reports that we received through
Arbonet were the milder form of West Nile fever. This year it's looking like it's running about half of them are the milder form of West Nile
fever, and that it's predominantly coming from the state of Colorado.
These things tend to oscillate over time, so that trend might not necessarily continue. I think the bottom line from our perspective is that we
know that there is a fair amount of severe disease that's occurring, and we fully expect a lot of that disease to show up in our disease reports
over the coming weeks.
Tony, do you have anything to add as to why there's so much disease activity in Colorado?
DR. MARFIN: Just to come back and say that the decision to report West Nile encephalitis or West Nile fever or both, really is a state decision
and it's based on the resources that states have available, and that in Colorado, because there has been utilization of a lot of the private
laboratories that are doing testing, they have been able to identify a lot more fever, and they choose to report it to us.
In terms of the importance of tracking West Nile fever cases, one has to remember that, you know, usually there are younger people that will
develop fever, although most of them don't develop any symptoms at all, and in fact, these people are living in neighborhoods where there may be
older people at risk. So we see a great deal of value to the tracking of West Nile fever so that we can assess human risk in some areas, some
neighborhoods, some counties, and I think it's a very valuable surveillance tool.
CDC MODERATOR: Thank you, Anita.
Next question, please, John.
OPERATOR: And that's from the line of Melanie Krum [ph], Fox News Channel. Please go ahead.
QUESTION: Hello. My question is actually looking towards the future, and how close are researchers to developing a West Nile vaccination for
humans? Is it months, is it years? And would a West Nile vaccine be something that the FDA would consider for fast-track approval?
DR. OSTROFF: Well, let me try to at least address the first part of your question. You know, there have been efforts that have been under way
since West Nile was first recognized in North America, which was in 1999, to develop vaccines not only for human use, but also for equine. And as
you probably are aware, the equine vaccine has been fully licensed by the Department of Agriculture and is being widely used in horses. Obviously,
there are a lot more steps that have to be taken in terms of the development, testing, for human vaccines, and these efforts are under way, being
principally coordinated by our colleagues at the National Institutes of Health, and we know that the vaccines are very close to going into Phase I
trials and would certainly hope that these are able to progress at a fairly rapid pace.
As far as what the FDA would do in terms of fast tracking them, I don't know if Dr. Nakhasi would want to make any comments. He's located in a
different part of FDA, but I think it's safe to say that the Department of Health and Human Services is committed to doing everything possible to
move these types of products forward so that they would be available for use.
DR. NAKHASI: This is Dr. Hira Nakhasi. I just want to echo your sentiment, Dr. Ostroff, as you mentioned, that I am in a different part of the
organization which takes care of the blood. The way we approach the donor screening testing, I think that's the overall commitment and sentiment
as you said, the agencies, that we would like to get these products as soon as possible, fast-track approvals, and make sure that the studies are
done. And we are virtually interacting with the people to do these things and get these things out as soon as possible.
CDC MODERATOR: Thank you, Melanie.
Next question, please, John.
OPERATOR: And that's from the line of Marilyn Marcione with Milwaukee Journal. Please go ahead.
CDC MODERATOR: Marilyn, are you there? Hello, Marilyn?
OPERATOR: And we will move on. We have a follow-up from John Lauerman with Bloomberg News. Please go ahead.
QUESTION: Thanks very much. What about using these tests to look at donated organs? I know that there were some cases last year that apparently
went through donated organs. Do these tests hold out promise for testing those tissues as well?
DR. OSTROFF: Dr. Marfin, do you want to take that, please?
DR. MARFIN: Yes, I will. Yes, you are correct. Last year the organ donor that resulted in infection in four organ recipients was our first clue
that there was virus being transmitted in the blood supply. We have been working very closely with HERSA, with the FDA, to look at extending the
use of these same tests that are being used in blood screening to organ donation. And this discussion is ongoing now. But you are correct, it
would be valuable possibly in screening organ donations as well.
The issues are very different though for screening organs and screening blood, and so I think that there were be ongoing discussion about that,
and it may result in a somewhat different testing algorithm, but I think it will play a role.
Dr. Nakhasi, do you have--
DR. NAKHASI: No. I think that's correct. I think we--as you know, we, from the very onset we encouraged the test kit manufacturers that the
indication for these tests should be to, in addition to screening the whole blood components, the other tissue and organ donors. And they are
pursuing this, and that means the test manufacturers are trying to look at that, and we are in constant touch with them, and see how these tests
can be extended to those indications.
CDC MODERATOR: Thank you, John.
John, we're ready for the next question, please.
OPERATOR: And we'll go back to the line of Marilyn Marcione. Please go ahead.
QUESTION: Hi, doctors. Thank you. I'm sorry. I had equipment issues on my end.
I'd like to ask about another article in MMWR, and that's could be related to West Nile, and that's the viral meningitis situation. I see that
it's not a nationally notifiable disease, but by putting this article here are you concerned that there's an increase? I see there are several
states with outbreaks. Can you talk a little bit about how that fits in with this picture?
DR. OSTROFF: Yeah. This is Steve Ostroff. I'll try to do that. Aseptic meningitis, of course, occurs fairly commonly. It's usually caused by a
number of different viruses and I think, as has been reported over the last couple of months, there are some areas of the country that are seeing
increased numbers of cases specifically due to a couple of viruses in the echovirus family, as is reported in the MMWR article.
One of the difficulties with these--with aseptic meningitis is that it does tend to peak in terms of activity at almost the same time of the year
as these mosquito-transmitted diseases, although these aseptic meningitis cases are not related to mosquitoes. I think that's one important point.
But the seasonal occurrence is similar to what we would see with West Nile. So there is opportunity to potentially confuse what the cause of
illness is. That's why it was important to make sure we got the information out about the fact that we were seeing some increases in aseptic
meningitis, and to make sure that from the standpoint of the health care provider that they go through the appropriate diagnostic algorithms to
determine what the specific cause is.
Most cases of aseptic meningitis that are caused by viruses tend to be milder than the types of meningitis that many of you report on, the
bacterial forms particularly from meningococcus, but they're still quite important. These disease, because many of these individuals are not
necessarily hospitalized and aren't necessarily have the appropriate diagnostics in order to definitively diagnose the cause of illness. That's
why in many of the states these aren't reportable and why aseptic meningitis specifically is not nationally reportable.
CDC MODERATOR: Thank you, Marilyn.
Next question, please, John.
OPERATOR: No further questions in queue.
CDC MODERATOR: All right. Well, thanks, everyone for joining us.
And thank you, John.
Listen to the telebriefing