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CDC Briefing on Public Health Investigation of Human Cases of H1N1 Flu (Swine Flu)

May 3, 2009, 1:00 p.m. EST

Glen Nowak: Thank you all for calling in today's press conference, our media update on the novel H1N1 virus situation. Today we have Dr. Anne Schuchat, Acting Deputy director for Science and Public Health at CDC, available to answer questions and give an update and Dr. Nancy Cox, the head of the CDC influenza division to answer questions as they arrive.  I will turn the briefing over to Dr. Anne Schuchat for an update on the H1N1 situation.  Dr. Schuchat?

Anne Schuchat: Thanks for joining us this afternoon. I want to give some brief remarks for today's update and then I'll answer all of your questions.  Today I think we do see some encouraging signs, but we are remaining cautious.  We have a new infectious disease, a novel H1N1 virus.  It's too soon for us to know exactly how this will involve or play out.  We need to be ready for the seasonal flu next fall as well as what this new H1N1 virus is going to do in the fall, and we're really working actively and aggressively to be one step ahead, both currently and then preparing for the fall.  The extent of spread of this virus in the U.S. and around the world is widespread, and it's possible that the W.H.O., the World Health Organization, will be continuing to re–evaluate the phasing.  Currently we're at phase five, but it's important to know that that issue is still being looked at.  The phases the W.H.O. talks about relate to how widespread infection is.  Not how severe it is. 

Today's case count for the United States is 226 confirmed cases, and those cases are occurring in 30 states.  That's up from 21 states yesterday.  Part of this increase is just catching up on the testing, and part of it is that we do think this virus is fairly widespread.  We know that most of the other states are actively working up cases, and we expect a number of additional states to confirm the virus in the days ahead.  The median age of cases is 17 years.  Still quite young people are primarily affected.  The cases do continue to occur –– the most recent confirmed case is April 29.  We have one confirmed death here in the U.S., and we have 30 hospitalizations that we know are related to the H1N1 strain of influenza.  I want to put the increasing cases and the increasing states in some context.  We do think this virus is widespread across the United States.  More people are getting flu.  More people are being tested for it, and most of those people are recovering.  We think that very few of the cases we have confirmation in are over 50.  They tend to be people who are younger.  Whether this will pan out over the weeks ahead, we don't know, but at this point it's a pattern that looks a little bit different from seasonal influenza.  We also know that the numbers are changing very quickly, and in the days ahead we expect to transition from talking about confirmed cases and states to other ways that we can describe the trends, whether things are getting better or getting worse around the country.  There are several encouraging signs.  We've heard reports that the H1N1 activity might be leveling off in Mexico.  It's too soon to be certain that's the case, but the patterns may vary at different states.  Some of the initial lab tests you've heard about were encouraging.  The absence of the virulence markers from the 1918 H1N1 pandemic and differences between this particular strain and the very virulent H5N1 influenza strain, but again, we don't know everything we need to know about how virulent this strain will be.  We have the positive isolates of influenza tested here in the CDC’s lab, GenBank, and so researchers will be able to access those and really, really take off on research on this particular virus. 

There's been a lot said about how is this particular virus different from seasonal influenza?  Seasonal influenza causes 36,000 deaths a year and 200,000 hospitalizations so it's a pretty important public health problem.  A big difference is that this is a virus that's totally new, and we don't expect large population immunity, and then another big difference is that this virus is increasing after the period where seasonal flu is usually decreasing, so we can't predict with certainty what the weeks and months ahead will look like.  We are planning to remain aggressive with this new virus and this new infectious disease, because it continues to be a rapidly evolving situation.  I don't think we're out of the woods yet, but I do think that people are cooperating and working together in really effective ways to try to limit the impact this virus has on health and to slow its spread.  We don't know if the virus will come back in the fall harder than it is right now, and, of course, that's one of the big concerns we have.  I want to tell you a few things about the CDC and public health community actions.  The Strategic National Stockpile by the end of today will be completing the deployment of the 11 million anti–viral regimens that we are sending to the states and program areas.  This is a 25% portion of the original allocation for the states.  HHS has begun purchasing an additional 13 million regimens of anti–viral.  We don't have an unlimited supply of anti–viral, but we're in much better shape than we were some years ago, and that focus for anti–virals right now is to treat people with severe influenza or to keep–– treat people with influenza–like illness who are at high risk for complications of the disease.  CDC and our partners have been active.  We've got more than 70 people in the field and more than 600 people here at CDC working on this response, and our science and surveillance are very active trying to understand the disease, the illness it's causing in people, and the impact that we can expect going forward. 

We're working very actively with the health care community and the public health community in clinical response and in public health surveillance and tracking, and we have continued to issue new guidance and update our earlier guidance.  We'll be releasing new guidance for clinicians about testing and treatment in this circumstance.  It's a bit different now than it was ten days ago when this was very, very new.  We'll also be re–evaluating many of our recommendations related to other community settings.  Looking forward, a lot of people are wondering about the big events of the spring, things like graduations and other big public gatherings.  I can tell you that this is an issue we are looking carefully at.  For the time being we do expect that approaches will vary from community to community and institution to institution.  In general, our feeling right now is that in general, cancelling public gatherings in the United States doesn't make sense.  There may be some local circumstances that are different that we definitely respect.  We really want people who are sick to stay home and not go to those big public gatherings, and we want the people at the big gatherings to remember how important it is to wash their hands, cover your coughs, and to take steps to reduce spread from you to other people. 

As we've said in the past several days, we're taking active steps together with FDA, NIH, and BARDA to begin the process of vaccine development for eventual production.  This is a multi–part process, and we can't promise that it will be produced or available.  This is something that is unpredictable for the seasonal flu.  It's even more unpredictable because it's a totally new strain of influenza virus, but the community that's expert in this area is very active and working together with manufacturing as well. 

In closing, I want to thank people for their interest, for staying connected with what's going on.  We're hitting some records here with eight million visitors to CDC's website a day now.  Apparently over 80,000 subscribers to Twitter who were dealing with this.  I guess we have one tweet per second related to the new H1N1 virus.  You recall –– I'm aware that it's a tweet not a twit.  Our YouTube videos from broken all records for CDC with 1.1 million viewers last week.  Now, we have really appreciated the viral spread of our educational messages and that's one of the best responses that we can have.  The way that we protect ourselves from a new virus is the way that we protect ourselves from seasonal flu.  Washing our hands, staying home when we're sick, not traveling when we're ill, keeping our kids out of school, and really staying informed.  We're trying to build on lessons that we've learned from the past, from outbreaks like SARS, totally new viruses that were spread through the respiratory route that the world community was able to contain and respond to effectively.  We're also building on all that we have been studying over the past few years related to pandemic preparedness and the pandemic influenza experiences of the past, but it's important for people to remember that no single action can interrupt this virus.  It's going to take a combination of actions.  Our goal continues to be the reduced and the public health impact of this new virus and to slow its spread to buy time to produce a vaccine for the fall and also to slow its spread so that we don't really overwhelm the health care system.  I think that there's probably lots of individual questions that people have, but with that I think I'll be closed for the formal opening and open the lines to questions.  The first question from the phone. 

Operator: The first question is from Maggie Fox from Reuters.  Your line is open. 

Maggie Fox:  Hi, thanks so much.  I'm wondering if it's too soon to say that you're as heartened as the Mexican officials are.  We still only have one death in the United States, although there's a steady spread.  There hasn't been the severity of cases.  If there were going to be a lot of severe cases, wouldn't they start showing by now? 

Dr. Schuchat: I'm heartened by the Mexican authorities' reports, but I am very cautious.  I know that influenza can be surprising and that the time course here in the United States is later.  We believe we're just on the upswing here and that in several parts of Mexico cases began quite a while ago, several weeks ago, so it's good news that we've only confirmed one death and we have 30 hospitalizations at this point, but it's too soon to say the extent of this disease.  From what I know about influenza, I do expect more cases, more severe cases, and I do expect more deaths, and I'm particularly concerned about what will happen in the fall.  Next question from the room. 

Ceci Connolly: I don't know if you or perhaps Dr. Cox could speak a little bit more about the re–assortment that occurs between humans and pigs and if it's going in one direction versus the other, what that can mean. 

Anne Schuchat: Right.  Let me make one brief comment, and then let Dr. Cox elaborate in the scientific lingo.  You know, we do know that in usual time influenza viruses in humans, circulate to humans and influenza viruses in pigs circulate to pigs, but it's possible for transmission from pigs to humans and from humans to pigs. Of course, there's also birds.  Re–assortment in the different–– from the different species is possible.  I think Dr. Cox will probably elaborate a little bit more technically on what we think the issues are. 

Nancy  Cox:  Thank you, Dr. Schuchat.  It's difficult to explain what is a fairly common and complex process in just a few words, but I'll try to do so.  Influenza viruses have segmented genomes.  That is, they have their genes in pieces.  If an individual host is infected by two different influenza viruses, whether that's from a pig, a bird, or a person, the two viruses can swap genes and the virus that emerges will have some genetic properties, some genetic segments from one virus along with the remaining genetic segments from the other virus.  What happens with pigs, it's really quite interesting, because pigs are susceptible not only to swine influenza viruses, but to Avian influenza viruses and human influenza viruses.  The pigs actually serve as a wonderful mixing vessel for influenza viruses to re–assort in new ways.  What we can say now with respect to the virus in pigs is that if pigs are infected with this new virus and some swine influenza viruses that are already circulating, there could be additional re–assortment of them.  Likewise, if a human were co–infected with one of the seasonal influenza viruses and this new H1N1 virus, we could have a virus re–assortment which emerges that has different properties from the two parental properties.  Hope that helps.

Ceci Connolly: Now that we're seeing it moving back and forth, any thoughts on where this one began? 

Dr. Cox: It's really impossible to know, but because we saw that all of the gene segments of this new H1N1 virus had their closest ancestors, each gene had its closest ancestral gene in swine influenza virus, our working hypothesis, but it was only a working hypothesis, was that re–assortment occurred in pigs.  It doesn't necessarily mean that that's where it occurred, but that was our working hypothesis based on the genetic relationship of each of the Gene segments. 

Dr. Schuchat: Before we take the next question, I want to make sure that people understand that origin, the ancestral origin of genes doesn't have any impact on our statement that you can't get this new novel H1N1 virus from eating pork or pork products.  Let's take the next question from the phone. 

Operator: The next is from Betsy McKay, Wall Street Journal.  Your line is open. 

Betsy McKay: Hi.  Thanks very much.  I actually just wanted to follow–up briefly on Ceci's question.  She asked most of my question.  You know, overall, how worried are you that what Dr. Cox is describing could actually happen, that there could be a re–assortment, that there could be public health implications of this virus from pigs and possibly back and forth? 

Anne Schuchat: I think it's important to say that we are concerned about this virus as it is in terms of being a new virus that is clearly transmittable from person to person and can cause illness that can be severe, so we are concerned with this new virus.  The possibility of additional re–assortment in terms of seasonal flu in the fall or this virus in the presence of the animal community is also a concern, and really emphasizes our ongoing effort for animal and human health to work closely together.  The more we can protect the animal community and the human community and collaborate, the more we can keep these kinds of interactions from occurring.  So promoting good veterinary and agricultural practices and good public health and medical care is a good idea.  I think that the prospect of re–assortment is always there with influenza, but even the strain that we have right now, we do think it's a major concern.  Next question from the phone. 

Operator: The next is from John Cohen, Science Magazine. Your line is open. 

John Cohen: Hi.  Thanks for taking my call.  I realize your efforts can slow influenza spread, but do you think that given that the U.S. has very sophisticated surveillance going on and Mexico has a surveillance effort as well, do you think it's possible to contain a new influenza virus like this one that moves from one species to another?  Is containment truly possible at the early stage so that it doesn't spread from the origin? 

Anne Schuchat: Okay.  We don't think that containment is possible now or that by the time we knew about this that containment was possible.  Containment, the idea of punching out the virus where it originates and keeping it from spreading to other communities is something that is part of our pandemic planning.  We originally thought if the avian or bird flu strain of virus emerged in a small community far away, and aggressively was responded to, we might be able to extinguish it and keep it from adapting well to people and spreading, becoming pandemic strain.  By the time we were aware of this, the new strain, it was in multiple locations and was transmitting frequently enough that it was not in our view containable.  On the other hand, good agricultural practices and excellent surveillance can play a good role in limiting the impact of disease, and I think in the future, you know, we shouldn't throw out the idea of containment.  It is quite possible that other circumstances would arise in the future where we would definitely want that tool in our tool kit.  Next question.  From the phone.  Sorry. 

Operator: Thank you.  Our next is from Richard Knox from National Public Radio.  Your line is open. 

Richard Knox: Thank you very much.  I appreciate the opportunity.  Two questions, if I may.  One of them has to do with the U.S. situation.  You mentioned 30 hospitalized cases, and I wonder if there's any information about those about how severe, whether any are in the ICU or so on and also about the U.S., there was a survey released by the New York health department indicating about one out of three students at the St. Francis prep students that were sick since April 8th, and I wonder if you think if this suggests an attack rate of 33 percent, how that compares with the seasonal flu and whether that's unexpected. 

Dr. Schuchat: The first question was about hospitalizations and severity.  I can say that information is being gathered.  From what I understand some of those cases were severe.  We are continuing to get support and information, and it's too soon for us to say the extent of the severity.  The important point is that seasonal influenza leads to hospitalizations.  About 200,000 people hospitalized each year from influenza.  One important difference between what we're seeing in hospitalizations here in the U.S. so far is that they are not in the age group, in general–– they're not in the age groups that typically are hospitalized for seasonal flu.  With seasonal flu, it's primarily the elderly and the very young who are hospitalized.  In our small sample so far of hospitalizations from this new H1N1 virus, it's in older children and younger adults.  These are early days, though in characterizing the hospitalizations, and this is one of the things that we'll be looking for more information on in the weeks ahead.  Your second question was about the New York City survey and the attack rate of about one–third of students.  First, I want to compliment the New York City health department for a terrific investigation.  We owe a lot to them for learning as much as they could early days in this environment and sharing it to so quickly with the rest of the public health community.  An attack rate of 33 percent is pretty normal for seasonal influenza.  We know that seasonal influenza spreads pretty easily and what we can learn from the New York City survey is that this virus spreads pretty easily in those high school students.  We do think that this virus is very transmissible, just like most influenza viruses adapted to humans are very transmissible.  What we don't know enough about it yet is very large populations is how severe it will be. The next question from the phone, please. 

Operator: The next is from Daniel Steinberger, CBS news.  Your line is open. 

Daniel Steinberger: Thanks for taking the call.  What are your school closing guidelines, and what are you recommending to schools?  Have you noticed something specifically on what's happening in Fort Worth, Texas, and their school closings?  Can you discuss that a little bit as well? 

Anne Schuchat: Yes, thank you for the question about school dismissals.  CDC has posted guidance for school dismissals, and I want to say two things, first off.  The first thing is that local authorities and jurisdictions have a lot more information about the circumstances of students and the community and the alternative services and what's really going to happen if you dismiss students from school, and we have a lot of respect for the local authorities in trying to make wise decisions dealing with the new infectious disease.  The second thing I want to say is that CDC is committed to learn as we go and to update our interim guidance regularly when the facts change or when we learn more about the benefits and average consequences of our guidance.  Our current guidance for school dismissal suggests that if there's a case identified in a school population, the authorities consider asking the students for a period of up to two weeks and that this might be considered for confirmed or probable cases at that school.  Also, that gatherings–– big social gatherings associated with that school be postponed or deferred as well.  Authorities can make decisions about other schools in the area.  That guidance was developed based on a very new situation, and the idea that closing the school or dismissing the students might decrease the transmission and slow the spread of this virus within the student population and beyond.  Of course, with school dismissals, there's a balance, because the goal is to decrease transmission, and it's important that those students don't just move and go gather together somewhere else.  It's also important that those students are having their needs met wherever they go.  If their school is closed and they're not getting lunch, for instance, or if they don't have appropriate child care available, then circumstances may differ.  We also know that the extent of transmission is different right now in different communities, so I think in terms of the Texas authorities, this is the time where local authorities are really putting their heads together around the circumstances.  The concern in the community, the amount of disease that they have seen, the benefits and disadvantages of dismissing the students.  I can also say that we're continuing to re–evaluate our guidance in conjunction with the partners.  Necessity question from the phone. 

Operator: The next is from Marilyn Chase, Bloomberg news.  Your line is open. 

Marilyn Chase: Yes, good afternoon.  Thank you for taking my call.  This question goes to Dr. Schuchat's remarks about the groups involved in preparing for vaccine development.  I would like to know, have you sent virus samples or seed stocks to any vaccine companies, which public health agencies currently hold it, and which companies will receive it?  Thank you. 

Anne Schuchat: We are in the process of growing up the seed strain for vaccines, and we have turned that seed strain over to an academic laboratory which is responsible for the reverse genetic preparation of the virus.  What I may do is actually let Dr. Cox elaborate on exactly where we are with the seed strain as well as the manufacturing question. 

Nancy Cox:  Thank you for that question.  We've moved very aggressively in the days since we first identified the two California cases to develop a vaccine virus which could be used by vaccine manufacturers.  There are a number of different approaches that can be used to make candidate vaccine viruses, and some of the vaccine manufacturers actually take the virus as it's grown in the laboratory and they use their own techniques to make specialized candidate vaccine viruses, so we have already distributed influenza viruses to some of those specialized vaccine manufacturers and to all of the partners who work with CDC and the World Health Organization around the world to make vaccine candidates–– vaccine candidate viruses that will grow well once they are handed over to vaccine manufacturers. This process is proceeding rapidly.  There are many things that are being done in parallel so that we will be ready to make pilot lots should that decision be made.  We'll go to the phone again for the next question. 

Operator: The next is from Arin Gencer at the Baltimore Sun. Your line is open. 

Arin Gencer: Hi.  Going back to some of the cases that are still probable and not yet confirmed, I know there's a backlog, obviously, in the lab down there, and I just was wondering if y'all have any sense of the timeline as to when, for example, the 15 cases in Maryland might get some kind of confirmation. 

Dr. Schuchat: The laboratories at the state and large city public health level as well as the CDC I would say are operating at full capacity right now.  One of the good things that happened over the past several days is we were able to ship out the new H1N1 influenza virus kits to the state public health laboratories in order that they would be able to confirm this new strain themselves so that in the days ahead we don't believe we'll have that category of probable cases, untypable at the state lab and awaiting confirmation here at CDC.  It was always our intent to get a new diagnostic test out to the states as rapidly as possible so we wouldn't have this type of backlog.  We know that it's difficult for communities and the public health authorities as they're trying to understand the circumstances, so the attempt right now is to make sure the information can be processed as quickly as possible, and I do apologize for the frustration in the meantime, but I think things will be fed out pretty quickly.  We're also issuing new guidance to clinicians about testing and typing.  You know, there's a certain amount of increased shipment of isolates to understand if this is a new strain or not.  We think we're at a point right now why we don't need to confirm every single person with a possible H1N1 influenza infection.  We're at a point where we know that the virus is in many places and we want to understand trends in a different way, so we have a couple different plans to deal with this backlog.  Improving the capacity at the state labs, and helping the clinicians focus on which specimens are important to send in for testing.  Also, we have our developing guidance for public about which illnesses really need to prompt a medical visit to get tested.  We hope with those few steps we'll be able to address the challenges of understanding what is and isn't the H1N1 virus.  Next question from the phone. 

Operator: The next is from Liz Szabo at USA Today

Liz Szabo: I would like to ask you about the vaccine.  If you are able to make one for the fall, how many doses would be available?  In other words, how many Americans would be able to get a vaccine? 

Dr. Schuchat: You know, it's early days to say exactly what production would look like.  There are a couple of factors.  One is who would be recommended to receive vaccine in the case of a vaccine production.  Would it be the whole population or some subset of the population?  For instance, we're still trying to understand whether the seniors might have protection already against this strain.  Whether the lack of illness that we've seen so far in older persons is because of preexisting protection or it's just because we haven't had enough time for those cases to be detected.  We don't know what population group we were going for.  A second factor is how well–– how easily it's going to be for this vaccine to be produced because each year the strains grow in a different way and the manufacturers are able to produce more or less.  This pilot lot that we're planning to be developed will also tell us how the vaccine would need to be formulated.  Whether a little dose would be enough to give protection or you would need a larger dose.  Whether with an adjuvant you could get away with less of the virus or you would need a larger dose.  Those types of variables factor into how easy it is to make very large numbers of doses of vaccine according to schedule, and so the planning that the U.S. pandemic preparedness effort had focused on was ideally to have enough vaccine production for every American to get two doses.  Manufacturing capacity is at an all–time high based on the pandemic preparedness that's gone through the past two years.  It's way too early to project whether we're going to go with large scale production of vaccine and how many doses would be produced.  Next question, please. Next question from the phone, if there are any.  Sorry.

Operator: The next is from Mike Stobbe, Associated Press.  Your line is open. 

Mike Stobbe: Hi.  Thanks for taking the call.  Doctor, you use the word widespread at the beginning of your comments.  Is that the first time you have used that word in describing the U.S. situation?  I have a follow–up. 

Dr. Schuchat: When I say that this virus is widespread, I mean that it is in many places, that the majority of states in the United States have detected this virus, and from what we know so far about the way it is spread, particularly from the New York City experience, I believe it is likely quite common in those communities where it's been detected.  That was what I meant by widespread that virtually all of the United States probably has this virus circulating now.  That doesn't mean that everybody is infected, but within the community the virus has arrived.  With seasonal influenza we often talk about detection of the virus as an important signal of the beginning of the season, and I would say that in most of the country right now this virus is there.  You had a follow–up?

Mike Stobbe: Yeah, thanks.  226 confirmed cases today.  That's a jump of 85 from yesterday.  Were all 226 confirmed by CDC, or are we starting to see some of the confirmations just from state labs being added to the CDC tally? 

Dr. Schuchat: You know, this is a mixture.  I would say the jump is catch–up.  Not that there was a big difference between one day and the next day in terms of the onset of illness.  Part of it is because the states are able to test themselves, and part of it is because we've gotten our systems a little bit more streamlined here to be able to deal with some of the backlog.  It's a mixture of states doing their own testing.  And because the states are now able to confirm themselves and because we know there are lots of probable cases out there, I expect the numbers to jump quite a bit in the next couple of days.  Time for one more question from the phone. 

Operator: The next question is from Denise Grady, the New York Times.  Your line is open. 

Denise Grady: Thank you.  Thank you very much.  Given the–– the finding in Canada yesterday, does there need to be more of a look at hog farms?  I mean, you mentioned good agricultural practices and surveillance, but can you tell us a little more about what you mean about it, about whether there is a possible role for this in this illness? 

Dr. Schuchat: You know, the U.S. Department of agriculture has the lead for these issues for the U.S. government, and they have been actively involved in this issue from the beginning really.  We worked closely with them on, you know, influenza matters and on the pandemic planning efforts we've been taking, so they do have a program to assess the situation and to assure that the practices we have on the hog farm and production community are good and to understand the situation on the ground.  I think for the details of what is going on and what we expect, I suggest contact the USDA, and if you need a contact there, we can probably provide it.  Thank you all, and I guess we'll probably talk with you tomorrow. 
End

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