Update on Distribution of H2N2 Influenza Strain
April 13, 2005
DR. GERBERDING: Good afternoon. Thank you for joining us here today. We're
going to provide an update on where things stand right now with the
inadvertent distribution of the H2N2 influenza A virus to a number of
laboratories around the world. I just really hope that we can put some
perspective into this discussion today. We want to leave you with one very
important message, and that is, while the risk of the situation is very low,
we're not taking any chances and we are doing everything we can to make sure
that there's no threat to human health.
Let me tell you what we know right now and then I'll comment on some
things that we don't know but are in the process of finding out, and then we
can review the steps that are under way to make sure that the virus that has
been distributed is destroyed and that the appropriate health monitoring is
The College of American Pathologists and three or four other organizations
that are responsible for testing the proficiency of laboratories around the
world inadvertently sent out proficiency testing panels that contained the
H2N2 influenza A virus. This virus is the virus that was associated with the
Asian flu pandemic in 1957, so it is a very important human virus in its
origin, it is a virus that we know can cause human disease, and obviously a
virus that we have not seen in this country for a long period of time. In
fact, the last known date when this particular strain of virus was
circulating was 1968. So anyone born after 1968 would not have had any
exposure to this and would presumably be completely susceptible. So the
concern is that our population does not have immunity to this H2N2 isolate,
particularly our younger people.
We do know that the virus was distributed to approximately 4,000 or more
laboratories. We don't know how many of the proficiency test panels went
out. We believe that the earliest dates that they were released was
September 10th of 2004, but we're verifying that by working with the
distributors and making sure that we can account for absolutely every single
lab. We know that, in total, the panels were sent to 18 countries, including
the United States and Canada, and we are working with officials in all of
these countries to take the steps necessary to contain the problem.
We also have very good surveillance for influenza in the United States. We
have not observed any unusual patterns of influenza this year, and in fact
the flu season is almost over in most parts of the country. We are not
finding any H2N2 isolates in our collection of flu strains--and let me just
say a word about how this works. When someone has the flu and a virus test
is done, the lab tests to determine whether it's flu A or flu B. And then,
in most of our labs, there's a further characterization to determine whether
it's an H1 or an H3 strain. If an H2 strain was included in that testing,
that strain would not normally be identifiable by the labs and they would
send it to the CDC. Part of what we do is characterize any strain that is
So we have not had any H2 strains come to us this year at all. In fact, as
I said, we haven't seen any of those since 1967 at CDC. So we are not
anticipating that there's an occult H2N2 flu circulating in the community,
because by now we would have been able to detect it.
We know that these proficiency test panels were to have been handled in
laboratories under Safety Level 2 precautions. That is the designation of
the kind strategies in a laboratory to protect workers and to protect
contamination. We at CDC believe that the best level of protection for these
kinds of novel flu viruses would really be Level 3. So part of our concern
for workers is that the labs would not have taken the extra precautions
necessary to be absolutely certain that there was no exposure. And as I
said, we believe that the Level 2 precautions would certainly protect the
workers, but we're erring on the side of extra caution, and in the future we
will be urgently recommending that a higher level of precaution be used for
any novel flu virus.
We also don't know about the specific strain of H2N2 that was used for
this proficiency test panel because the strain has been passed in the
laboratory many, many times. Our experience with viruses indicates that when
a virus is used in the lab like this, it very often loses some of its
infectivity so that it can't any longer infect people efficiently. We have
no proof of that in this case, but that's what we've seen when other viruses
have gone through this kind of process and various kinds of challenges have
been conducted with them. So it's possible that this strain of virus
actually poses a very, very low threat of transmission efficiently and to
the public, but we are not, again, taking any chances and we can't assume
that. So we have to err on the side of caution.
Here are some of the steps that are in progress right now to minimize
further any risk. First of all, CDC had advised the College of American
Pathologists and the other organizations responsible for distributing these
proficiency test panels to destroy any virus that remains from that process,
to completely autoclave it so that it is gone; and to do that immediately
and then to report within 24 hours back to the College of American
Pathologists or the other source that these steps have been taken. We are
also asking laboratories who have been involved in this kind of testing to
monitor their workers, and if the worker has recently had exposure to these
proficiency test panels, to test them for influenza if they develop any
symptoms or signs that are even remotely suggestive of influenza. And of
course, if such an illness develops, the individual should be tested for
influenza, CDC should be notified, and that sample should come here.
The World Health Organization has contacted the ministers of health in the
other 17 countries to be sure that similar processes are in place in each
and every laboratory that may have received these proficiency test panels.
And we are all collaborating very effectively to be sure that we don't miss
any labs and that we have a complete understanding of each and every
laboratory that may have been participating in the testing with this panel.
It's important to understand that proficiency testing is a good thing.
It's the way we assure that labs have the kinds of quality measures in place
that would allow them to accurately be able to identify a novel virus. But
we are very concerned that this particular strain of virus was used for
proficiency testing, and we will be working with the College and with the
other organizations to try to make decisions about how we can assure
effective laboratory practices without placing lab workers or the public at
any unnecessary risk from exposure to a novel influenza strain like this
one. So those steps are in progress, and the Department of Health and Human
Services, under Secretary Leavitt's direction, is reviewing all procedures
relating to handling influenza viruses to be sure that any opportunities for
something like this to happen in the future are prevented. And we will be
fully cooperating with those efforts as we go forward.
Let me just end, one more time, with an important perspective here.
There's no evidence that any person has acquired H2N2, and most of these
laboratories have already destroyed their proficiency test panels. But we
are ensuring that all steps are taken to identify every lab that may have
the virus and that it is quickly destroyed. We are doing everything we can,
without taking any chances that this virus could infect an individual or
spread to the public at large. And if we learn more about the situation as
we go forward, we'll certainly update you. We expect that we don't have all
the information today because this is still an unfolding story. So as we
learn more, we will definitely update you.
I want to take this opportunity to introduce my colleague Dr. Nancy Cox,
who is here today. Nancy is the leader of our influenza branch at CDC. She
has been a very busy person leading a very extraordinary group of scientists
across our agency for this problem, as well as the avian influenza problem,
the flu vaccine shortage this year, and a number of other challenges that
influenza has presented to us in recent. So I thank Nancy and certainly
appreciate an incredible scientific capability that she and her team bring
to bear in solving this particular flu issue.
So let me stop and take some questions.
QUESTION: Laura Biel from the Dallas Morning News.
Can you give more details, first about how this error was made, and second
about how it was discovered?
DR. GERBERDING: Thank you. The organizations that are responsible for
testing and approving or accrediting the quality of laboratories routinely
send out panels of unknown organisms to determine if the lab can accurately
identify them. And included in those panels sometimes are influenza viruses
because that's such an important part of laboratory functioning. In this
case, a company called Meridian Bioscience, Inc., from Cincinnati, Ohio, was
the organization that created the proficiency test panels, and they used
this H2N2 strain in their influenza test panels, perhaps because this strain
of flu is a reference strain and it's known to grow fairly readily and it's
a relatively easy one to process. So they made the decision to include this
particular influenza A isolate. We don't have other details about why or how
that decision was made and who participated in the decision. We also at this
point can't comment on what the College and the other organizations
responsible for accreditation actually knew or understood about the content
of the proficiency test panels, and that's something that we will be
exploring further as we go forward.
So what happened was that one of the labs who was participating in the
proficiency testing in Canada identified an unknown virus and, on further
characterization, discovered that they had an H2N2 virus in the laboratory.
And that was, of course, of great concern to them, recognizing that that
would be the first introduction of H2N2 since 1968. And so they
appropriately did a very thorough assessment of what was going on there and
consulted with CDC. I believe Dr. Cox was contacted. So CDC contributed to
the process of evaluating was this an isolate from a patient or was this
something that had happened in the laboratory by mistake. And it turned out
the detective work in the lab made the determination that the source of this
virus was in fact the proficiency test panel. That information was relayed
to CDC on March 26th, and we have been working through the understanding of
the scope and magnitude of the distribution of these proficiency test panels
So there have been a number of steps and I could delineate some of them.
March 26th was when the Public Health Agency of Canada informed CDC and the
World Health Organization. March 31st, Public Health of Canada and CDC
advised the laboratory to undertake the full stem-to-stern assessment of
what was going on in the lab.
That laboratory investigation was basically completed by the 8th of April.
On that day there were additional investigations to trace the source of the
sample, including work done by the National Microbiological Laboratory in
Canada, and their conclusion was that it was in fact related to the
proficiency testing package that had come from the College of American
Pathologists. CDC contacted the College and Meridian, the contract producer
of the test kits that day, and advised them to initiate immediate actions to
inform all labs that had received the test panels that they need to be
On the 9th, the health officials conducted further communication to
determine what each could learn about the scope and magnitude of the problem
so that we were sure to include all of the countries that were potentially
recipients of these test panels. And obviously, the World Health
Organization has been very engaged in this, in providing that kind of
On April 11th, we sent information to the College for the recipient labs,
to specify in detail the manner in which the specimens should be destroyed
and the process for reporting back to the College that the specimens indeed
had been destroyed.
And then finally, on April 12th, we learned that additional organizations
besides the College of American Pathologists had been engaged in proficiency
testing, so we initiated the same procedures for this broader group. If we
discover that additional labs have received the proficiency test materials,
we will of course repeat this process until we have accounted for each and
every one of the test kits. That will take some time, but I can assure you
that we're doing everything we can at CDC, and the World Health Organization
is doing everything it can, to speed this up and make sure the channels of
communication are completely open.
That's a very long answer to your question, but I did want to emphasize
the time line, that this is all happening very quickly and we're working as
fast as we can to solve the problem and also look to the future to make sure
that we prevent it from ever happening again.
QUESTION: Laura Abels from CBS 46 News here in Atlanta.
Do we know if any of the proficiency test panels have arrived in Atlanta,
DR. GERBERDING: I don't have that information. I'm not sure if we have
here, at CDC, the specific geographic distribution of the test panel, but
that's likely something we'll know over time.
I wouldn't be surprised because we have many labs in the region and all
labs that are accredited participate in proficiency testing. But we can't
confirm that right now.
QUESTION: Hi. I'm Beth Galvin with Channel 5 and thank you for talking
with us today.
I wanted to ask you a couple questions. How are these specimens destroyed?
If you could explain, in simple language. Also you talked about Safety Level
2, Safety Level 3. What kind of precautions were being taken in a Safety
Level 2 lab? And finally, what would you say to people at home who are, you
know, hear this and think this is kind a scary. We're talking about a very
DR. GERBERDING: Let me answer the last question first. I think it's the
most important one. For people at home hearing about this, we want to
reassure you that right now we have no evidence of any health threat to
anyone in the community from this situation and we don't have any evidence
that even a lab worker has been affected by this.
But we're erring on the side of caution and we are monitoring and we have
been monitoring all through the flu season, so that even if something
happened as far back as September and an unusual flu virus had emerged, we
would certainly know about it by now.
So our main focus at this point is just on the kits that have recently
been distributed, the panels that have recently been distributed because
those would be the people who would be most likely to be in an incubation
period for flu, and as we learn more about the timing and the use of these
panels at the various laboratories, we'll probably be able to narrow this
down to a much smaller list of potential hazard.
In terms of the specifics of what happens under different levels of safety
precautions, we can give you a short summary of that. I think it's on our
Internet but we can provide that to you.
But just to explain, in a Biosafety Level 3 facility, the entire
processing of a specimen is done under a specialized hood where there is
containment of the material and no chance of anybody working in that
environment, of inhaling or breathing in a specimen.
Because influenza is transmissible through that mechanism, the precautions
are designed to avoid any respiratory or other exposure to the virus.
So people working under those conditions not only wear gloves and
appropriate gowns but they also have respiratory protection to be sure that
they're not getting any contact with the flu and it's completely contained
in a hood so that it's not released into the community.
QUESTION: And in a Level 2, what kind of precautions are taken or how are
DR. GERBERDING: The specimens are--in Level 2 precautions, it doesn't
require that kind of biosafety hood that has the very high level air
containment. The destruction process is what we call autoclaving, which
basically uses a combination of steam and heat to bring the material up to a
temperature where it is not possible for viruses to survive. It's a routine,
it's done all the time in labs everyday, across our country, and it's the
best way to eliminate this kind of hazard.
May I take a telephone question, please.
MODERATOR: Thank you, Dr. Gerberding. Lisa Stark with ABC News, your line
is now open.
QUESTION: Dr. Gerberding, thank you. Let me ask you, a number of other
countries had already bumped this particular virus up to a Level 3. Was the
CDC remiss in still having this virus at a Level 2? Should it have already
gone to a higher safety level as it has in many other countries?
DR. GERBERDING: The decisions about the level of safety containment for
viruses are made collaboratively between CDC and NIH, and CDC has already
issued its interim recommendations about raising the level of precaution to
Level 3. Those haven't been finalized yet but you can be sure we will
expedite the review and decision on that method.
I don't want to imply that Level 2 is unsafe. We just believe that when
we're dealing with something that is even theoretically a risk to the
public, we should use the most prudent level of biosafety precautions, and
that, in our mind, is a Level 3 precaution.
Another question from the telephone, please.
MODERATOR: Thank you. Anita Manning with USA Today, your line is now open.
QUESTION: Thank you very much.
Can you tell us anything about whether this strain was attenuated, and if
it were attenuated--you made some slight reference to it-- if it were, and
somebody were exposed to it, what would the effect be?
And the other question I have is to go back to this Level 2, this H2N2
strain was a BSL 2 strain. So should the labs have somehow subtyped it, or
when they do these proficiency tests, do they just identify it as Influenza
A? Do they then go on to subtype it?
DR. GERBERDING: Let me take your first question about the concept of
attenuation. What we mean by attenuation, that the virus is somehow altered
so that it's less infectious or causes less severe disease. This strain is a
reference strain. That means that it is one derived from the outbreak of
Asian flu that occurred in 1957, and beyond.
But because it's been utilized as a reference strain in laboratories,
especially during those years when it was also circulating in people, this
particular version has been passed in cell culture, in laboratories, over
and over and over again. And that's just a process that often leads to
inadvertent attenuation, because viruses adapt when they're not inside of
We don't know if the virus has attenuated, we wouldn't be surprised if it
was, but we're not assuming that that would be the case. I just mentioned it
because it is an additional perspective that offers us some reassurance that
the risk here is not high. But we're not banking on that by any stretch of
the imagination and we are continuing to be aggressive about destroying the
With your question about the typing that's done under proficiency test
circumstances, the main importance in most laboratories, and what the intent
of the proficiency test is for influenza, is for labs often to just
distinguish whether it's an Influenza A or an Influenza B. In some
laboratories, they can go on to characterize it further as a H1 virus or an
H3 virus, and because we're concerned about avian influenza, more and more
of our laboratories supported by CDC and our state health departments, are
also able to distinguish H5. But virus strains that can't be characterized
or need to be characterized are sent to reference laboratories, including
CDC, where we can do the complete and comprehensive assessment of the virus.
So for purposes of accreditation, a lab mainly needs to know it's
influenza and they need to know whether it's an A or a B strain of
influenza, and so the virus would not have been characterized further and
that's why we didn't learn about this earlier on in the process.
Can I take another phone question, please.
MODERATOR: Thank you. Rob Stein with the Washington Post, your line is now
QUESTION: Yes. Thank you, Dr. Gerberding. First off, I was just wondering
if you could tell us how many labs have you confirmed have already destroyed
their samples and do you have any kind of tally on how many have been
destroyed and how many are left out there?
And the second question was do you have any indication on how this mistake
happened? Was it that the lab didn't realize what it was sending or it
realized what it was sending and didn't realize that they shouldn't have
been sending it?
DR. GERBERDING: The number of labs that are engaged in destroying the
virus is a work in progress right now and the first step of that
communication is back to the source organization, so we're capturing that
information on the fly, and I can't give you a frame on that right now. It's
So explanation for why H2N2 was used in the proficiency test panel by
Meridian Bioscience and/or why the accrediting organizations chose to use
those particular panels is something that we have not clarified at this
point in time.
I'm sure it was not an inadvertent use, because it would be almost
impossible to believe that they didn't know they were dealing with an H2N2.
It was probably a situation where the advantages of using a strain that
grows well and can be easily manipulated in the lab were the driving force,
without really considering that even a test strain in a panel could
potentially cause a hazard, not only to the workers in the lab but to the
people in the community.
So one of the steps that we are taking as an agency is to assemble our
best experts, and we do have experts here at CDC on proficiency testing. We
have worked with the American College of Pathologists in the past to try to
improve the safety of proficiency testing and we are going to assemble the
necessary experts and put this on a fast track to really create CDC guidance
on proficiency testing that we hope these organizations will take seriously,
participate in, and then use as quickly as we can get the expert input
It's not a simple matter because the balance here is making sure that labs
can test for dangerous pathogens, and at the same time they need to be able
to do that in a way that is as safe as possible.
Any questions here in the room? Go ahead.
QUESTION: Are laboratory workers being tested or offered prophylaxis?
DR. GERBERDING: There would be no indication for testing laboratory
workers at this point in time. Again, the focus will narrow down to those
that have had most recent exposure to the test panels.
If someone was working with a test panel last fall, it really doesn't
matter because the opportunity for infection, the incubation period is long
So we will be only concerned about those that had relatively recent
exposure, within days of the time that we initiated the monitoring, and I'm
sure that's going to be a very small number of people, but we don't know how
many will be included in that group.
And so since the risk of transmission is very low, we have elected to
recommend a monitoring process that's part of the information we've sent out
to the affected laboratories, and the early assessment of anyone presenting
with any illness that could conceivably be early influenza.
I'll take another telephone question, please.
MODERATOR: Thank you. Maggie Fox with Reuters, your line is now open.
QUESTION: Thanks very much.
Can you tell us, Dr. Gerberding, has anyone ever been known to have caught
a flu virus or any other infection from one of these proficiency panels?
DR. GERBERDING: I can't answer that question today. I'm not aware of any
but I think it's something that we'll be exploring as we go about the
process of developing guidance.
If it happens, it's an extremely unusual procedure, and as I said, while
we believe at least in theory that Level 3 precautions would be warranted
for dealing with a novel flu virus, Level 2 precautions, when properly
utilized, are also able to protect workers from this kind of exposure.
So those precautions are part of the standard operating procedure in
laboratories, and particularly accredited laboratories, which these are.
That's why they're participating in the proficiency testing program.
If you've ever been in a lab, you know that the SOP in the lab is to treat
specimens, especially unknown specimens with a great deal of respect, and I
think that the quantitative hazard posed here is very low but we can't
assume it's zero, and again, that's why we're erring on the side of caution
and be sure to eliminate any potential risk of exposure through this
Let me take another telephone question.
MODERATOR: Thank you. Larry Altman from the New York Times, your line is
QUESTION: Yes. Two questions to clarify points that have been raised, and
then two new questions. First, it's not clear how you're saying this was
attributed to the panel in the laboratory in Canada, because if it was from
the proficiency panel, they would have known that from the beginning. So
somehow, the way this is being described, it sounds like the virus got loose
and was detected.
The second is the number of 4,000 labs being tested for proficiency sounds
high. Do most community laboratories test for influenza? I thought most of
them were sent to the health department and so forth. If you could clarify
And then the new questions are why wasn't this information released by CDC
earlier, and what authority does CDC have either before or such an event to
regulate or oversee the distribution of such pathogens?
DR. GERBERDING: I'm not sure that the exact mechanism by which the
Canadian laboratory identified the H2N2 will ever be known but the
hypothesis under which we're operating right now is that because this
particular reference strain does grow so easily, that in the conditions that
the lab was using there was potentially a crossover.
So that what was thought to be a human influenza specimen in culture was
actually contaminated with the proficiency test strain that was perhaps
being used under the same hood.
I don't know that that's the case and I'm sure those details will be
There was no evidence that the virus was "on the loose" in the laboratory
and it took a great deal of investigation to identify that in fact the
source of the H2 was the test panel, but I would also refer you to speak
with the people from the lab there, because they would be able to give you
the most accurate understanding of that.
There are actually many, many more laboratories, Larry, than you might
realize. Keep in mind that we're talking about 18 countries here as well, so
this isn't just a U.S.-based collection of laboratories. This is an
international set of laboratories. And so what the total number is remains
to be seen and most clinical laboratories associated with health care
organizations can determine that they have influenza and many of them are
able to make the distinction between H1 and H3 as well.
That's been increasingly relevant in these days where flu is in the news.
The last question about CDC's authority to regulate the process of
managing this kind of situation. As you know, in general, CDC is not a
regulatory agency. We have regulatory authority to deal with select agents
that are relevant to bioterrorism. Avian influenza strains, if they are of
the highly pathogenic nature, are included as select agents, and so in that
case we do have the regulatory authority and responsibility to assure the
safe distribution and use of these viruses.
But regular flu viruses are not considered to be select agents and so we
are not empowered in our regulatory capacity to deal with them.
And this is one of those advantages and disadvantages of being a
nonregulatory agency. But I must say that as you know from most of the work
we do, the kind of cooperation that we have in engaging organizations with a
credible reputation of places like the College of American Pathologists, we
feel that we can accomplish the goal of improving laboratory safety without
imposing regulatory efforts.
But, in fact, that's why the accreditation process is so important,
because accredited laboratories not only have to be able to accurately
detect pathogens but they also have to adhere to the appropriate standards
of biosafety and biosafety containment in order to sustain their
So the regulatory authority there really comes through the accreditation
process and not directly from the CDC.
I'll take another telephone question, please.
MODERATOR: Thank you. Kevin Freking with the Associated Press, your line
is now open.
QUESTION: Thank you. Doctor when did the CDC decide that it needed to
issue more clear guidelines on how labs should be handling these samples?
DR. GERBERDING: I would have to ask Dr. Cox when we evolved our internal
recommendations about enhancing the safety precautions for influenza. It
didn't happen this week. I can tell you that right now.
Do you know when those were first drafted? Want to come to the microphone.
DR. COX: Yes. The CDC works with the NIH and a whole variety of influenza
experts to determine the level of biocontainment for a whole variety of
pathogens, including influenza viruses.
And so over the past several months, we have been working with our
partners at NIH to revise what is called the agent summary statement for our
microbiological laboratory safety guidelines, and so this is a process that
has been ongoing for a number of months.
The documents are still in draft form but as Dr. Gerberding mentioned, we
will be working very hard to get these new recommendations finalized as soon
DR. GERBERDING: I think I can take one more telephone question.
MODERATOR: Thank you. Helen Branswell with the Canadian press, your line
is now open.
QUESTION: Thank you very much. I'm sorry to do this but my question was
answered earlier. Thank you.
DR. GERBERDING: I'm sorry. I'll take the next question.
MODERATOR: Thank you. We'll go on to the next question. Our next question
comes from Maryn McKenna with the Atlanta Journal-Constitution. Your line is
QUESTION: Hi. Thanks for doing this.
Just some clarification. Dr. Gerberding, is it clear at this point that
the source of the virus was Meridian Bioscience or was it some organization
further back in the chain than them?
And wherever this originated, is it clear that they did know that this was
the 1957 H2N2, rather than--or a daughter virus of--the pathogen virus of
that rather than it being something that had been accidentally mislabeled?
And then my broader question is how confident are you that this is a "one
off" occurrence and that there's not a broader vulnerability here to
potentially dangerous viruses being accidentally, or negligently circulated
in this manner?
DR. GERBERDING: Our information right now is that Meridian Bioscience
created these proficiency test panels, knowing that the H2N2 virus was in it
and that there is no proximate source beyond that that's relevant to the
situation that we're dealing with.
The content and the approach to proficiency testing is something that
continues to evolve as the needs for laboratories evolve, and as I mentioned
earlier, CDC has a tradition of working collaboratively with the College of
American Pathologists to improve on the safety of the proficiency testing
In the past, for example, similar situations where proficiency test
viruses were sometimes mixed up in the lab with human specimens
under the same hood occurred when laboratories were conducting their
proficiency testing at the same time they were busy with flu season or other
high-priority work. So one of the things that we worked on in the 1990s was
the timing of the proficiency testing so that labs were concentrating on
that when the individuals weren't busy with other activities. And I think
when we sit down to go through the guidance for how this should be done in
the future, we're going to be looking not just at what's tested, but looking
at when it's tested, who's testing it, under what levels of safety it's
being tested, and what are the criteria for inclusion of pathogens in the
Inclusion of pathogens is an important part of accrediting laboratories,
as I mentioned. We have to know that labs have the ability to detect these
organisms, because that's what they're there for. We want them to be able to
do this and we need to assure that they can. But at the same time, we have
to also be sure that we don't put an unnecessary risk into the system. And
we can certainly evaluate the proficiency of testing for influenza without
using a novel strain that we haven't seen in recent years, and just
completely take that hazard off the table. And that is what our intent is.
So let me just conclude today by thanking you for coming for the briefing
on such short notice. I personally want to thank our influenza branch and
our colleagues in the Department of Health and Human Services who have been
working virtually around the clock since news of this possibility first
became clear. I can't tell you how much work goes on in tracking down all of
these laboratories and assuring that we have cast a broad net.
We are, again, seeing no evidence of a human health hazard here, but we
must take these steps to be sure that all of this H2N2 is eliminated, and
that's exactly what we're working on right now. I think this is CDC in
action and I really appreciate and respect the hard work that's gone into
this from Dr. Cox and her team.
Thank you all for your interest in this story and for helping us reassure
the public. Thank you.
[END OF PRESS BRIEFING.]
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