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Update on Anthrax Investigations
with Dr. Bradley Perkins
November 9, 2001
CDC MODERATOR: Good afternoon. Today, Dr. Bradley Perkins will be the
speaker for our telebriefing. Dr. Perkins is going to discuss an article
that's no available online in CDC's Emerging Infectious Diseases Journal. It
discusses the first ten cases of inhalational anthrax relating to a
DR. PERKINS: Good afternoon. The first ten cases of inhalational anthrax
related to bioterrorism shares similarities with previously reported
inhalational anthrax cases, but also has some important differences that are
outlined in the article that's available online in the Emerging Infectious
Diseases Journal. The article summarizes each of the ten cases and notes
that the survival rate among the group of recent cases was higher than
previously had been expected.
Prior to October 2001, the last case of inhalational anthrax in the United
States occurred in 1976. Between October 4th and November 2nd, CDC, and
state and local health officials confirmed ten cases of inhalational
anthrax. Of these ten patients, 70 percent were male, and the average age
was 56 years. Four of these individuals died. Previous studies indicated a
survival rate of less than 15 percent for persons with inhalational anthrax.
The survival rate in this group of ten patients is at 60 percent.
The combination of antibiotic therapy begun during the initial phase of
illness and aggressive supportive care may have markedly improved the
survival rate for the recent ten patients. All but one of the patients in
this investigation were Postal workers, mail handlers, sorters or
journalists who were known to be or believed to have processed, handled or
received letters containing Bacillus anthracis spores.
We think this is critical information to urgently get out to the front-line
clinicians that may be seeing future cases of anthrax in either its
inhalational or cutaneous form and look forward to their continuous support
in early identification and treatment of these individuals.
CDC MODERATOR: Okay, John, we're now ready for questions.
AT&T MODERATOR: Certainly. And once again, ladies and gentlemen, if you do
have a question at this time, please press the one on your touch tone phone.
Our first question today is from the line of Sanjay Baht with the Palm Beach
Post. Please go ahead.
QUESTION: Yes. Thank you for holding these briefings. I have two questions.
The first, in light of September 11th and the anthrax attacks, there's been
a lot of discussion about expanding the laboratory response network and
training at the local level. Is expanding the number of EIS officers also a
priority and how big of an expansion would you like to see?
DR. PERKINS: I think that the EIS officers, during the conduct of this
investigation, have been critical because they are a very highly trained,
mobile and rapid--rapid-deployment force that can do essentially most all of
the critical epidemiologic investigation functions that are needed to do
I think consideration of expanding the class of the EIS officers has been
discussed at CDC at the highest levels. I don't know that there have been
any decisions made about expanding the EIS officer class, but they have been
a critical asset of CDC during this investigation.
QUESTION: [Technical problem with phone line.] Can you tell us anything
about the select agent registry, such as how many labs are registered with
the CDC [inaudible] select [inaudible] or the direction of the changes the
CDC would like to see in current shipping or storage rules?
DR. PERKINS: I'm sorry. I did not hear the beginning of your question.
DR. PERKINS: Can you restate?
QUESTION: Yeah. Can you tell us anything about the select agent registry,
such as how many labs are currently registered to mail select agents or what
direction the CDC would like to see in the changes made to shipping or
DR. PERKINS: No, I cannot comment on that question.
AT&T MODERATOR: Our next question is from the line of Gina Colloda with the
New York Times. Please go ahead.
QUESTION: I have two questions. First of all, you may note that on Table 1
it's supposed to be ten patients and we can only see eight. I don't know
why, but it seems like the last two were cut off. But I was really curious
to know whether there's anything you can look at in the laboratory findings
or anything else which would differentiate the people who lived from the
people who died.
And, number two, I was wondering, when you talk about the numbers of people,
the distribution of the patients, when you say that 70 percent were male,
with an average of 56 years, that sort of is like a numerator, but we don't
know what the denominator is. I mean, like were most of the people who were
in that mail room males? Do they tend to be middle-aged or, in other words,
is this a significant finding or not, in terms of the number of people who
may have been exposed?
So those are my two questions.
DR. PERKINS: Taking your second question first, we're working to compare the
age distribution, the demographic comparisons between the cases and the
occupational groups that they represent, working with the Post Office to do
that, primarily, and that information is not completely together or known.
I will say that, anecdotally, working with the Postal Service and being in
these environments that the age distribution of the inhalational cases we've
seen is slightly older than what you would expect based on what's been
observed in those settings, but we're working to get more quantitative
comparisons to draw that conclusion more firmly.
Your question, I'm not sure, can you restate that?
QUESTION: The age distribution is slightly older than what you'd expect
based on what's been observed, but what about the gender distribution, were
they mostly men in these Postal facilities?
DR. PERKINS: Yes, men are disproportionately represented in some of the
settings where cases have occurred, and again that's part of the
demographics comparison that we're carrying out.
AT&T MODERATOR: We'll go to the next question from--
CDC MODERATOR: John, I'm sorry. Let me interrupt you for a minute. Gina had
a question about the tables on the other cases.
CDC MODERATOR: Gina, it has the day with the way you printed it. The table
was set up in a Landscape format. You probably printed the text. That's in
Portrait. Simply change it to Landscape on your printer, and you'll get all
QUESTION: Okay. But my question was beyond that. The question was can you
tell the difference, in looking at this data, between those who lived and
those who died? In other words, were there any distinguishing or other
findings in the people who survived this inhalational anthrax as compared to
those who died of it?
DR. PERKINS: In general, the persons that did poorly and died presented for
medical attention, at least at the time of admission, with more critical
illness than those that survived, suggesting that early identification and
prompt treatment was important to the increased survival rate that we saw
given the experience with the patients that have been treated, do we have a
preferred treatment when we think we have meningitis? And the other question
is do we have a sense of the role of the protein inhibitors like Clindamycin
in treatments of serious cases?
DR. PERKINS: Yes. Those are both very good questions. We think that
treatment with multiple drugs containing at least one chloroquinolone class
drug is important, and that the selection of particular agents should be
driven by considerations of involving the use of at least one drug that may
be--may have activity in inhibiting the production of anthrax toxins, such
as Clindamycin as a representative of that group.
We also feel like that in cases where meningitis is suspected or
demonstrated that choosing appropriate antibiotics that penetrate into the
cerebral spinal fluid is also an important clinical consideration because
among the antibiotics that could be chosen from, there is variable
penetration into that protected central nervous space.
The other, I think, critical factor to recognize is that cephalosporin
should not be used for treatment of anthrax because of the innate capability
that Bacillus anthraces has to produce a cephalosporinase that inhibits the
antibacterial activity of the cephalosporin such as stef-triaxon.
AT&T MODERATOR: Thank you. Our next question is from Pete Williams with NBC.
Please go ahead.
QUESTION: Dr. Perkins, can you tell us how old the Ames strain is? There's
some indication that it's been around since the early 1900s, some indication
that it was isolated later. How long has it been around?
DR. PERKINS: The Ames strain has been certainly through the most recent
decades a strain of preference among researchers working on a variety of
aspects in anthrax, either in animal models or in other research settings. I
do not know the precise date that that isolate was obtained, but certainly
for the last two decades it has been a strain of choice among researchers
working in this area.
AT&T MODERATOR: Thank you. Our next question is from Miriam Selko with CNN.
Please go ahead.
QUESTION: Hi. Thank you for these teleconferences. Can you tell us if the
CDC told Iowa State University to destroy their strain of the Ames anthrax,
and if so, why?
DR. PERKINS: I cannot tell you that. I know that I have not been in any way
involved in making any such recommendations.
CDC MODERATOR: Next question.
AT&T MODERATOR: Thank you, and that's from the line of Jeremy Meniere with
The Chicago Tribune. Please go ahead.
QUESTION: Hi. Thanks very much. Let's talk a little bit--two questions. One
is in addition to antibiotics, you mentioned aggressive treatment as a
factor in [inaudible]. Would you talk about some of what doctors have been
able to do in that respect that they might not have done in cases decades
ago? Are we talking about chest tubes or other things like that that might
have been a factor?
Also I'd like you to talk a little bit about the incubation time which seems
to be maybe less here than some studies have indicated in the past.
DR. PERKINS: Yeah. Those are--that's a good question. I think that
the--there's a range of things that may have not been done the same over the
last century that are now common practice in settings of severe infectious
diseases like anthrax, and they range from aggressive intravenous hydration
therapy, the availability of pressor drugs that allow the maintenance of a
normal blood pressure in the setting of severe infections.
In addition, there's mechanical ventilatory support, intubation with
machines to assist in breathing.
The other thing that looks like it probably was critical that would not have
been routinely practiced, certainly in the earlier parts of the last
century, was the aggressive use of pleurosynthesis to remove bloody fluid
that we saw collect in the lung space of many of these individuals, and that
had to be done on a number of occasions with some of these folks. And if
that's not done, that obviously mechanically compresses the lung tissue and
further compromises respiratory function. So I think that was also
In one case, although there's not a lot of data to base this on that would
be reasonable clinical consideration, one of the patients underwent
plasmapheresis in an effort to try remove some of the toxin that may have
been in the blood.
So I think it's probably a variety of things, but I think the hypothesis
that improved technology to support people with serious infectious diseases
as the body recovers from the infection resulting in improved survival is
quite a valid hypothesis based on, you know, a number of technologies that
are currently available.
CDC MODERATOR: Next question.
AT&T MODERATOR: Thank you. And that's from Steph Warrenstein with Knight
Ridder. Please go ahead.
QUESTION: Yes. Looking at your--thanks again for having these. Looking again
at your article, and I know you were meeting last week and continuing to
meet about research that has to be done not in the field, but in the lab, to
better understand anthrax and the way--why some people get exposed. Does
this--especially looking at why some people died and also why some people
got infected and others did not, what specific research questions do you
want to look at in the lab resulting from your quick studies here?
In other words, in the lab, what are you specifically looking for right now?
DR. PERKINS: I think one of the hypotheses that's critical and lends itself
very well to further laboratory research is the utility of this classes of
antibiotics that inhibit protein synthesis and may thereby decrease
production of the toxins through which anthrax does its damage. And we've
already been in contact with a number of experts in this area, and I think
that that's a critical research question in the context of therapy.
Another thing that we're actively exploring in terms of additional
adjunctive therapy is the use of antiserum which is a preparation that would
contain antibodies directed against the specific toxin components of the B.
anthraces. And this is a time-proven approach to adjunctive therapy in
toxin-mediated diseases such as anthrax, and we're aggressively pursuing
research to support that modality as adjunctive therapy in cases of serious
disease that don't look like they're going to respond to aggressive
antibiotic use alone.
AT&T MODERATOR: Thank you. Our next question is from Maggie Fox with
Reuters. Please go ahead.
QUESTION: Thanks again. Can I follow up on that? Can you tell us a bit more
about this antiserum in lay language and also I got very excited about the
gastrointestinal symptoms of some of the patients that are outlined in your
paper until I read farther down and found out that that was also common in
the Sverdlovsk incident.
But can you tell us in lay terms about how the bacteria moved into the
gastrointestinal system and caused those problems?
DR. PERKINS: I think, and there's not a huge amount of data addressing this
issue, but I think that the gastrointestinal symptoms that we're seeing are
likely to be a manifestation of severe, diffuse toxemia. And when these
toxins get into the blood, and there's two toxins, there's a lethal toxin
which causes cell death and an edema toxin which causes swelling of tissues,
when those get into the blood, they obviously move throughout the entire
system and create symptoms throughout the body.
And so I don't think it's a phenomenon of the bacteria preferentially
affecting the gastrointestinal system. I think what we're seeing is the
impact of widespread toxemia, of widespread toxins circulating in the blood,
and you've got that edema factor or edema toxin and lethal toxin exerting
its disease-producing tendency on the gastrointestinal system at the same
time it's doing that on the heart, and on the lungs, and a number of the
major organs in the body.
What specific question did you have regarding the--
QUESTION: The antiserum. What is this stuff? What's it called, and is it
something that is used? I have not heard this, except as theoretical, but
you said it was a time-proven approach to adjunctive therapy.
DR. PERKINS: Yes, it is. There's a variety of antitoxins that have been used
over a long period of time. I mean, treatment for botulism, for example,
botulism is a toxin-mediated disease for which the primary therapy is an
antitoxin, which is an antibody that goes in and finds the toxin,
neutralizes it, in some instances, and prepares it to be cleared by other
inflammatory cells in the body, and these antibodies can be produced in a
variety of ways.
Using human cells in culture, for example, you can produce large amounts of
monoclonal antibodies. These are antibodies that have very specific
activities, and they're all the same, and you can produce those and you can
use them as adjunctive therapy. This is something that has been a major area
of research for a long period of time.
AT&T MODERATOR: Thank you. Our next question is from Laura Mechler with the
Associated Press. Please go ahead.
QUESTION: Thanks. I have a couple of questions for you.
First, in the New York City investigation, I understand there's a plan to
test the subway routes along which the hospital worker traveled, but they
hadn't yet determined how they were going to do that. Can you tell us
anything about that?
And related to that, what else do you plan in terms of the investigation
this weekend? Are there new routes to your planning?
And, finally, we're hearing that there may be a new case in New York City.
Do you know anything about that?
DR. PERKINS: Certainly, we are not aware of any new cases in New York City
at this time. Folks from CDC continue to vigorously support the
investigation of the possible circumstances of exposure that's resulted in
the inhalational case in New York City, but specifics regarding plans for
additional environmental sampling at this time would need to be directed to
the New York City Health Department.
AT&T MODERATOR: Thank you. That's from the line of Kim Dixon with Bloomberg
News. Please go ahead.
QUESTION: Hi. Thanks. I have two questions.
The first is about the widespread, I guess, availability of the Ames strain.
I know you said it was the choice among researchers for the past two
decades. Can it be estimated how many labs actually contain the Ames strain?
There's some reports that there are really like less than 10 that actually
would have this particular infectious strain.
And, two, could you comment about what the CDC is doing to look at the
possible mortality rate associated with the smallpox vaccine in light of the
fact that the government is ramping up and asking drug makers to come in and
help it make more vaccine?
DR. PERKINS: I cannot comment on the smallpox issue. That's not my area of
expertise. I lead the group that has responsibility for anthrax. Smallpox is
done by other folks here.
In regard to the number of laboratories that may have the Ames strain, I do
not know the answer to that question. CDC monitors the movement of select
agents as they're moved from laboratory to laboratory, but we do not know
the number of laboratories that actually have this strain in their
collection of bacterial strains in their laboratory.
AT&T MODERATOR: Thanks. Our next question is from Laurie Garrett with News
Day. Please go ahead.
QUESTION: Thank you. My question has to do with dose.
We've been hearing every imaginable possible dose described as necessary
inhalation dose for anthrax from 9 or 3 spores all the way to 55,000. Did
close examination of these ten cases offer any further elucidation on this?
Is there a safe dose? Is there such a thing as a threshold dose for
exposure? Do you believe in threshold theory?
DR. PERKINS: The ten cases that are reporting in the Emerging Infectious
Diseases Journal really don't offer any opportunity to better clarify the
number of anthrax spores that may be required for infection.
The variability that you hear among anthrax experts or other scientists as
to the number of spores requires I think reflects a number of things.
Paramount among those things are probably that for different people, a
different infectious dose may be required, and that is seen with normal
biologic phenomena with many infectious diseases. Obviously, it will be
extremely difficult to establish with great certainty what the average
amount of spores needed to cause inhalational anthrax is in a human.
What we do know is that there are environments with some level of spores
present, particularly outdoor environments in areas where animal epidemics
occur of anthrax, and we know that in those environments, we do not see
inhalational anthrax among persons that worked routinely in those
environments. So there clearly is a safe level of anthrax spore
contamination. These spores are widely distributed really across the globe
in many different locations where we don't see inhalational anthrax.
Extrapolating those data to the safe level of contamination in occupational
settings is an area of active and vigorous pursuit here at CDC and among all
of our partners. We know that some level is likely to represent a negligible
human health risk. Defining that level and relating it to the occurrence of
cutaneous and inhalational disease is something we're working very
aggressively to try to do right now based on all available data.
AT&T MODERATOR: Thank you. Our next question is from Claus Marr with Inside
Washington. Please go ahead.
QUESTION: Thank you. I have a couple of questions for you. One is regarding
an interim guideline for investigation of and response to anthrax exposures
that was released today. It says here that "closing of a facility should not
be done based only on the identification of anthrax from samples of
environmental surfaces or based only on the identification of cutaneous
anthrax." I was just wondering why CDC decided not to close buildings when
people get skin anthrax.
The second is a question regarding respirators that workers are being asked
to use. On October 24th, CDC said workers should use respirators with a
99.7-percent efficiency and a week later that was changed to respirators
that are not as efficient, that only have a 95-percent efficiency, and I was
just wondering what that decision was based on to change this.
DR. PERKINS: There are folks here at CDC that have been working with a
variety of partners, including the U.S. Postal Service to try to establish
the right mask to recommend in the Postal settings that we have the most
concern about in regard to inhalational anthrax. And this has been an area
of intensive focus by CDC, and there were a variety of technical and
practical aspects that went into making specific recommendations. I don't
know all of those aspects, but those decisions were based on the soundest
science available regarding the risk and the ability of the Postal Service
to implement those prevention modalities.
I think you should also recognize that these are interim guidelines, and we
will be constantly reevaluating and assessing the effectiveness and the
degree to which these recommendations can be implemented in an effective
Your other question regarded when the CDC interim recommendations regarding
building closure. Can you restate that question?
QUESTION: Yes. It says here that--it was from today, Interim Guidelines for
Investigation of and Response to Anthrax Exposures. And it says,
"closing a facility" or "facilities should not be done based only on the
identification of anthrax from samples of environmental surfaces and based
only on the identification of cutaneous anthrax cases."
DR. PERKINS: Right. We recognize that as a result of the bioterrorism
attacks that have occurred since early October that there has been
contamination of a number of places in the mail system. A kind of
cross-contamination that we think has occurred is resulting in very low
levels of spores in potentially a very large number of places. We don't know
how many places are going to end up having some low level of contamination,
but we know of many at this point.
And also during this period of time we've done intensive surveillance,
looking for cases of cutaneous or inhalational anthrax, and what we can
conclude by observing that there's fairly extensive environmental
contamination as a result of these incidents, but a very limited number of
cases of cutaneous disease is that the risk is extremely low, and that we
think that that risk can be mitigated by cleaning up these areas of
environmental contamination and practicing vigilant mail-handling practice,
looking for suspicious mail.
Of course, if there's cross-contamination, it may not be suspicious, but
good handwashing following handling of mail should mitigate the very low
risk that we recognize may be there as a result of cross-contamination. We
don't think that that situation requires the closure of a building.
AT&T MODERATOR: Thank you. Our next question is from the line of Jill
Carroll with The Wall Street Journal. Please go ahead.
QUESTION: Hi. Thank you for holding these briefings. They're very helpful.
Two questions. One is in the research that you're looking at, different
environments, now that anthrax can be spread like indoors, I want to know
what things you've learned from that so far. And also from the 10 cases,
anything that showed up in the 10 cases that showed a new way anthrax could
be spread, or some people have a lower tolerance? It might help either in
the Kathy Nguyen case in New York City or in general understanding how
DR. PERKINS: I wish I could tell that that kind of finding was clearly
evident from the 10 cases we're reported, but really the most striking
finding is that the risk was focused in very tightly-defined occupational
groups that were the focus, either intentionally or unintentionally, of
these current bioterrorism attacks.
That kind of occupational risk is traditionally quite helpful to physicians
who are seeing patients that, you know, that could have anthrax, but in this
case where, you know, it's unclear that these attacks will continue in this
manner or whether they might change in some manner, it's potentially less
useful than in many traditional public health investigations.
Your other question was?
QUESTION: On the research you're doing in other, you know, indoor settings,
that kind of thing, where anthrax--how it's going, anything you're learning
right now that's new on how anthrax can be spread or infected?
DR. PERKINS: I think the most important thing that we're currently learning
is that there are many sites of environmental contamination in occupational
studies that are not related to occurrence of human disease. That's good
news and bad news. I mean we don't want our environments, our occupational
environments or any other environments contaminated with B. anthraces
spores. I would rather not have them there. You know, that's the bad news.
The good news is that there's clearly going to be a level of environmental
contamination that does not represent a health risk for cutaneous disease or
for inhalational disease.
AT&T MODERATOR: Thank you. Our next question is from Ellen Beck with The
United Press International. Please go ahead.
QUESTION: Thank you very much. Are you, given the fact that you're still
actively investigating in the New York area, and I'm sure in the other key
areas as well, are you at any point considering pulling back the number of
people that you have in the field in Washington, New York, New Jersey, et
cetera? Or have you pulled back the number of field investigators or
technicians that are actively pursuing this?
DR. PERKINS: We're continuing to vigorously support local and state health
department needs in all four of the major sites of the investigation, and in
some cases our efforts are, and our focus, are shifting a little bit.
One of the current things that we're shifting additional people to work on
are monitoring people that have been recommended for prolonged courses of
antibiotics, 60 days of antibiotics for prevention of inhalational disease.
We want to know if there's any adverse event or adverse impacts that occur
because of them taking those antibiotics because it's unusual that you have
this large a number of people on these antibiotics for this long a time, and
we want to be aware of any adverse events that occur.
The other thing that we're trying to make sure happens is that all of the
people that we recommended take 60 days of antibiotics actually take 60 days
of antibiotics. So we're looking for strategies to promote adherence to
those recommendations because we think it's critical that they complete that
course so that they don't get sick.
AT&T MODERATOR: Thank you. Our next question is from the line of Dan Fergano
with USA Today. Please go ahead.
QUESTION: Hi. Thanks again for having these briefings. A couple of questions
about recognizing anthrax. Are you recommending chest x-rays as sort of
first and best way to identify anthrax when people come into it? And I also
had a question about the patient histories you put together. I'm reading
that eight of 10 patients first came in, received antibiotics. The six who
received fluoroquinolones were the ones who survived. Is that a common
denominator in these folks?
DR. PERKINS: Let me take your first, your chest x-ray question first. This
is a little tricky because I think what the paper clearly shows is that all
of these cases had abnormal chest x-rays and that gives you--that does give
the clinician something to work with.
However, you know, the early prodrome for these patients is typical for many
respiratory diseases that physicians might not usually get a chest x-ray
for. And so weighing--it's still going to be a challenge for the clinician
to weigh the need to obtain chest x-rays in persons that may have anthrax
among the range of diagnostic possibilities. And obviously respiratory
disease like the kind that is seen and can have the symptoms of early
anthrax is extraordinarily common in the United States. And we want to
balance the use of chest x-rays carefully as we try to pick the needle out
of the haystack here for early identification of patients that might have
anthrax. So it's useful information that all the chest x-rays are abnormal
in these patients, but it has to be in the clinical setting when you're
looking at a specific patient, that information has to be balanced very
carefully against the frequency of other respiratory disease.
And your question about the use of fluoroquinolones, I think that we do
consider fluoroquinolones to be a foundational therapy for the treatment of
severe illness resulting from Bacillus anthraces infection, and I think the
cases, as you mentioned, suggest that that's true.
You know, that should be just the foundation, though, and there should be
serious consideration of adding at least one or two different antibiotics to
that foundation based on whether the presentation is consistent with
meningitis or not, and the opinion about the need for a class of antibiotics
that might exhibit protein synthesis and decrease the level of toxins in the
CDC MODERATOR: John, we have time for one more question.
AT&T MODERATOR: Thank you. And that will be from the line of Rod Hendin with
CBS News. Please go ahead.
QUESTION: Thank you very much for the conference call. Just a follow-up. You
mentioned about--the question about how many labs have the Ames strain. My
question is under Federal law and guidelines, is it required that anyone who
transports or possesses anthrax in any form, in any amount, for any reason,
must register that with the CDC.
DR. PERKINS: I'm not an expert in the select agent rule, but I think that is
the general concept behind the select agent rule is that it monitors the
transport of these select agents from laboratory to laboratory.
CDC MODERATOR: Thank you, ladies and gentlemen, for participating in today's
telebriefing. A transcript will be available online.
AT&T MODERATOR: And, ladies and gentlemen, that does conclude your
conference for today. We thank you for your participation, and you may now