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CDC Telebriefing on Investigation of Human Cases of H1N1 Flu

May 18, 2009, 12 noon ET

Dave Daigle: Thank you. This is Dave Daigle from CDC Media Relations.  Today we’re going to do a brief update on the novel H1N1 outbreak.  Doctor Anne Schuchat will provide a brief statement and then take questions.  Thanks very much. 

Anne Schuchat: Good afternoon, everyone.  My first message to you is the H1N1 virus is not going away, despite what you may have heard.  As you know, the World Health Assembly is convening this week in Geneva, and leadership from both CDC and the Department of Health and Human Services is at the Assembly.  We are expecting the H1N1 issue to dominate the meeting, and I wanted to alert you to Director General Margaret Chan's statement from the WHO.  She said that influenza viruses are the ultimate moving target, and I think that really captures that scenario we're coping with right now.  This novel H1N1 virus is still circulating in the United States.  People are continuing to get sick, to get hospitalized, and unfortunately, to die.  At this point, there are six deaths that have been reported officially.  And, you know, we feel for the families that are experiencing those losses. 

As of today, there are 22 states around the country that are reporting widespread or regional influenza activity.  And unfortunately, based on the trends we're seeing, we do expect more illness, more hospitalizations and more deaths.  You may have heard that New York City and a few other places have had a number of outbreaks in schools, and some of them have issued recommendations for school closures at individual schools that have been affected. Those measures are consistent with the school guidance that we have updated, which suggests that there is a need for a localized response.  The illness severity that we're seeing continues to be pretty similar to what is caused by seasonal influenza, and we feel this means we need to remain vigilant.  We are now experiencing higher levels of influenza-like illness than is normal for this time of year.  We're also seeing numerous outbreaks in schools, which is also very unusual for this time of year.  Influenza is always serious, and influenza viruses are very unpredictable.  So unfortunately, it's uncertain right now how severe this outbreak will be in terms of the ultimate illness and mortality toll that it takes, or whether this virus will turn out to be worse than others that we've handled through the seasonal flu experience. 

Things could change quickly, and we do continue our efforts to prepare, particularly for the fall, where history tells us we might have a second wave of this new virus.  As of today, our official case counts are a total of 5,123 cases throughout the U.S.  We are seeing some geographic variation in the H1N1 flu activity, with activity appearing to be highest right now in the Pacific Northwest and the Southwest.  We know that our case counts are very incomplete.  They are just what we call the tip of the iceberg.  We're also looking at influenza-like illness, and we're seeing more reports of influenza-like illness from our outpatient visits that are monitored than would be typical for this time of year.  There have been over 200 hospitalizations, and, as I mentioned, six fatalities.  The illness that we're seeing and the hospitalizations that we're seeing are primarily in younger people.  Between 5 and 24 is the age group of the majority of cases so far.  And unlike the seasonal flu, we're seeing relatively few cases or hospitalizations in people over 65.  That's a very different feature that seems to be holding up through the surveillance that we're doing. 

In terms of the international situation, the WHO latest figures stand at 8,480 confirmed cases in 39 countries; recently added to the countries that have had at least one case are India, Malaysia and Turkey.  Japan is now describing the first cases of in-country transmission, and those are being further investigated.  And I want to mention a little bit about Mexico.  As you know, Mexico has been hard-hit, similarly to the United States.  But the overall trend appears to be downward in Mexico with more sporadic cases rather than the larger reports we were seeing earlier.  On Friday, the CDC and the Department of State issued updated travel advice.  We downgraded our travel advice for Mexico.  Earlier, we had recommended that travelers defer nonessential travel.  But since Friday, our advice went down to a precaution.  Our main advice now is for those people who are at risk of complications from influenza because of underlying illness, pregnancy, or advanced age, that they ought to check with their health care provider before embarking on a trip.  But so that we think that's an important change in our travel recommendations, and want to make sure people know that.  We do think it's fine for most people to travel to Mexico at this point.  As I've mentioned, the numbers that we give you are really not as helpful as the patterns.  And so I want to alert you to our website where we are continuing to use our routine seasonal flu systems, which we call FluView, and you'll see there a lot of different ways of describing what's going on.  A map that shows the states that have had widespread disease or regional disease, as well as the trends in the virologic testing and the influenza like illness. 

We do see in that system that the seasonal influenza viruses are continuing to circulate.  But about half of all of the influenza viruses we're seeing recently are this novel H1N1 virus.  Some people have been asking: has the virus changed? is it mutating or causing more severe disease?  From the stains that we’ve tested, there is no evidence right now of any mutation toward a more virulent strain, but of course influenza viruses do change and they can change and we will continue to look at them and track whether the virus is acquiring resistance, whether other features are changing that would be important as we move forward towards our control efforts, or even towards vaccination development.  We do think that the way the virus is spreading in the U.S. we are not out of the woods, and disease is continuing.  Our CDC efforts continue fairly aggressively.  We still have more than 80 people deployed in the field, and we have continued to support the laboratories and states here in the U.S., as well as in countries shipping our diagnostic kits to 95 labs in 50 states, and to 237 labs in 107 countries. 

At this point, 40 of the states here in the U.S. have got validated testing going on.  And that is really good news, meaning they don't -- they no longer need to have us confirm their results for them.  We're in active discussions regarding vaccine development and potential production.  CDC and others are working on development of a seed strain to make a candidate virus that could be turned over to manufacturing for production.  This is in very active stages of discussion right now.  Because, as you know, if you want to make a vaccine, it takes several months before it can become available, depending on how the manufacturing and clinical trials go.  You may also have been hearing about WHO and whether or not they will change their phase to a phase 6.  We're currently at Phase 5.  The Phase 6 designation has not been decided upon.  A Phase 6 means that the virus is spreading in a sustained way, in at least two regions of the world.  And we haven't -- that hasn't been officially declared.  It's important to know that we're seeing sustained spread here in the U.S., and we're acting very aggressively.  And so if it changed to a Phase 6 would have less impact for us here in the U.S. than for countries that haven't yet gone into full -- a full court press on this virus. 

I want to just close by saying that I think it's important to dispel the idea that we're out of the woods, or that this was a problem that really didn't merit response.  I think that we continue to see illness, it's a new virus, it's capable of causing severe disease.  We hope that it will not continue to cause illness and outbreaks in the Southern hemisphere the way it's been causing problems here in the U.S.  But we really need to continue to have our guard up, and to continue to be vigilant as we look towards the summer in the Southern hemisphere and the fall back here in the U.S.  So, you know, the final comment is influenza is unpredictable, and we really need to stay attuned to that, to be prepared for surprises in the days and weeks ahead.  So let me take some questions from the phone, please. 

Dave Daigle: Thank you, Doctor Schuchat.  And my apologies, I forgot to mention that Dr. Schuchat is our Director of Immunization and Respiratory Disease Center.  And with that, Operator, please open the line for questions.

Operator: Thank you.  At this time if you would like to ask a question, you may press star 1, and the first question is Maggie Fox, "Reuters”. Your line is open.

Maggie Fox: Good afternoon. Thank you very much. I want to ask Dr. Schuchat, given that we still don't really quite understand the pattern of disease and whether it's really disproportionately affecting younger people and why, is the way the testing is being done, the policy for testing, and not testing every case, will that give you the information you need to know to understand what the true denominator is, and what the true geographical pattern of the disease is?

Anne Schuchat: We're using a variety of systems to understand the pattern of disease, and which people are at greatest risk for illness or complications.  I do think that the tendency for younger people to affect -- to be affected is persisting in our evaluations.  Initially, we thought maybe this is just the first cases we're seeing, but that's been a trend over time, over several weeks.  It could be that in the fall older people are more affected, or over the weeks ahead, we'll see more cases.  But particularly when we look in detail at the hospitalized patients, we aren't seeing many seniors in that group.  And that's very unusual for seasonal influenza.  We think that our systems, like the ones that track influenza-like illness and some systems that look at emergency room visits or syndromic surveillance that some of the states maintain can be very helpful in understanding whether things are getting better or getting worse.  But we're also carrying out a number of field investigations.  Those 80-some people that are deployed are helping states with their challenges, or helping Mexico with their challenges.  But they're also intensively evaluating the detail of patients who are ill, including those who are hospitalized, and really trying to nail down some of those missing variables that we have. 

Dave Daigle:  Thank you, Maggie.  The next question, please. 

Operator: The next question is from Betsy McKay at the "Wall Street Journal."  Your line is open.

Betsy McKay: Hi, thanks. Dr. Schuchat, I wanted to follow up on the same theme about whether you’ve learned anything new about why this disease seems to be hitting younger people.  And so I wondered if you know or have evidence showing that older people have been exposed.  For example, have the school children in New York City passed it to their parents, grandparents or other adults, older adults in the community?  I mean, you know, elderly people?  And also, is there any credence to this hypothesis that has been going around that older adults may indeed have some immunity? 

Anne Schuchat: Thanks. Those are two good questions.  We do have some information to shed light on that -- observation that more children or teens are affected.  We've been looking in some of the field investigations with our colleagues in the states at the attack rates in households, looking at what happens to other members of the family when one person has this influenza-like illness or the H1N1 strain confirmed.  And what we see in the data so far is that the people under 18 are more likely to have infection when another person in the family is infected.  It may be that they're more -- the transmission is a bit more active in the younger population than in the older population.  So what we call age-specific attack rates in the households do suggest a difference in transmission to younger people versus older people.  Now, from the literature from other infectious diseases and from some infectious disease modeling, we believe that children are very good at transmitting infectious diseases.  They have lots of social contacts, and in particular, younger children may shed the virus for a longer period of time.  We are looking at viral shedding in some of the field investigations, but I don't have those data yet.  You also asked about the older population.  And certainly one of our working hypotheses is that older adults may have some preexisting protection against this virus due to exposure they had long ago to some other virus that might have been somewhat related.  We haven't gotten that totally confirmed through laboratory testing, but it's an active working hypothesis.  Of course, the alternate hypothesis is that it just may take longer for this virus to make its way into the senior population.  If kids hang around with other kids, and seniors hang around with other seniors, and the virus is really spreading rapidly among the kids, it just may take a bit of time, and then it may enter that senior population more aggressively than it has so far. 

Dave Daigle: Thank you, Betsy.  Next question, please, operator. 

Operator: One moment.  Next is from Elizabeth Weise from "USA today" your line is open. 

Elizabeth Weise: Hi, thanks for taking my call.  I have two questions. First, quickly, where is the CDC in the decision-making process on a vaccine, and secondly, given the death rates we're seeing in the United States, can you give us a metric to compare those two with seasonal influenzas this low, high, and are you seeing what's actually killing people?  Is that any different than it would be in a regular seasonal influenza outbreak? 

Anne Schuchat: Great.  Okay.  You know, CDC is just one part of the government that will be contributing to decisions about vaccine development, vaccine production, and then ultimately vaccine -- a vaccine program.  And those are three different decisions.  The parts of the government that are engaged in this include CDC, the FDA, the NIH, parts of health and human services, including the assistant secretary for preparedness and response.  And our -- all of these groups are working very actively in discussions to understand the decision points that lie ahead.  So the first step is well under way, the development of that candidate virus that could be handed off for vaccine development.  And active decisions about the steps that would follow thereafter. 

You know, the death rate -- are we seeing more fatalities than we would expect with seasonal influenza, or a higher proportion of illness than with seasonal influenza?  I think our best estimate right now is that the fatality is likely a little bit higher than seasonal influenza, but not necessarily substantially higher.  On the other hand, the hospitalizations that we're tracking have this disproportionate occurrence among younger persons.  That's very unusual to have, you know, so many people under 20 requiring hospitalization and in some of those intensive care units.  We're trying to actively investigate those and get better characteristics of what the illness looks like.  We have not yet found strong evidence for bacterial pneumonia that might be complicating an influenza illness.  That's one of the hypotheses people have had about why people might need to be hospitalized.  It's something that we look for, we don't yet have a final answer on that, but so far, we believe it's a little bit more of a viral pneumonia pattern than a later secondary bacterial pneumonia pattern.  And so as our cause of death data gets better, we really don't have big enough numbers right now to shed a lot of light on that.  It's one of the things we're looking at in conjunction with international colleagues.  So I think that's an important finding.  You know, as people look back at the 1918 pandemic, it was actually looking through autopsy material and reports that people came to interesting conclusions about causes of death that were very important in that pandemic. 

Dave Daigle: Thank you, Beth. Next question, please, operator.

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

John Cohen: Hi. Thank you for taking my call.  Apparently other countries have weighed in at the World Health Assembly about the decision to move from phase 5 to 6, urging Dr. Chan to do that.  Has the U.S. government or CDC representatives weighed in on this- at the meeting, and if not, why not? 

Anne Schuchat: I don't know the answer to that.  I'm sorry. 

Dave Daigle: Next question, please, operator. 

Operator: The next is from Daniel DeNoon, WebMD.  Your line is open. 

Daniel DeNoon:  Thank you very much, Doctor Schuchat.  Good afternoon -- good morning, I guess, starting a new week.  The finding that the viral cases, serious cases tend to be viral, does that- rather than bacterial- does that suggest that this virus has a special tropism for lung cells -- is there something different about this virus virologically that seems to suggest that kind of pathology?  And along the same lines, Dr. Chan in her address today was talking about the presence of diarrhea or vomiting in some 25 percent of cases.  Do you have any evidence of that kind of shedding, and could you talk about the implications of that kind of shed?  Thank you. 

Anne Schuchat: You know, I think it's too soon for me to make a grand conclusion about the viral pneumonia question.  It's something we want to look more actively at.  The diarrheal – the gastrointestinal systems is something that we are definitely seeing here in the U.S. in an important proportion of cases.  This is a feature that differs from seasonal influenza, about a quarter of our cases where we have the right kind of clinical data have vomiting or diarrhea on their presentation, not just the usual high fever and respiratory symptoms.  I think that's an important feature that needs to be looked at.  Interestingly, some of our data suggests that children may be more likely to have that nausea and vomiting versus adults with this new virus.  So there is probably going to be a lot of interesting findings as biologists and scientists take a better look at this virus and some of the clinical and epidemiologic patterns that we see.  We're still collecting data and trying to share with you as we get it. 
Dave Daigle: Thank you, Daniel. Next question, please, operator.

Operator: The next is from Donna Young, “Bioworld Today.”  Your line is open.

Donna Young: Hi. Thank you for taking my question.  I know you had also mentioned today that you're seeing a lot more of the seasonal influenza coming in later, you know, like May.  This is really late for that flu to come in.  And how can they be certain that what they're seeing is actually seasonal influenza and not like a completely different virus from the H1N1 and the regular seasonal influenza virus that was, you know, hitting earlier in the year?  Is there -- are they -- like, when they're testing, I assuming what they're doing is ruling out whether it's H1N1.  But are they also ruling out whether it is also a completely different influenza that was striking during the winter, like in January? 

Anne Schuchat: No.  We would be doing additional testing to make sure that the newer -- that the viruses we're seeing are consistent with the seasonal flu strains.  You know, part of what we do here at the CDC as an international -- as a WHO international collaborating center is characterize the viruses from seasonal flu.  That can contribute to strain selection for next year's -- next year's influenza vaccine.  And we do the testing not just of this novel H1N1 strain, but of the seasonal strain.  So we are continuing to see strains of influenza B, influenza H3N2, and the regular seasonal H1N1 continuing to circulate.  But about half of the isolates that are being tested these days, either here or in the states are this novel H1N1.  And we don't know what's going to happen in the fall, whether we'll see anymore of this H1N1, whether it would even replace the old H1N1, or whether we’ll have the four kinds of influenza circulating at the same time, or over different months next year.  So lots of -- lots of really important questions that we just unfortunately don't have answers to. 

Dave Daigle: Thank you, Donna.  Next question, please, operator. 

Operator: The next is from Lisa Schnirring, CIDRAP news. Your line is open. 

Lisa Schnirring: Hi, thanks for taking my call.  I’m wondering what you think might happen. School is going to be out in most places in a couple of weeks.  And how do you think that might affect community spread of the new flu? 

Anne Schuchat: We are very interested in that question.  You know, the school circumstances involve lots of people in a particular place, with lots of mixing.  Whether children will be congregating in the similar environments in summer, perhaps on summer camps or on trips, as the school groups or something, you know, might be similar to the way that kids are congregating in a school environment.  On the other hand, in most of the U.S., the season will change quite a bit in the summer, and those conditions, the summer months, the warm and some of humidity circumstances may be less conducive to influenza virus circulating, at least for seasonal flu.  So we -- we would love to see a decrease in cases, and to see the end of these outbreaks that are affecting schools.  But my influenza expert colleagues tell me, you know, there have been influenza outbreaks in camps, even just with seasonal influenza, and so we really need to be alert to that possibility. 

Dave Daigle: Thank you, Lisa.  Next question, please, operator. 

Operator: The next is from Richard Knox, "National Public Radio."  Your line is open. 

Richard Knox: Thanks very much.  I appreciate the opportunity.  One thing, just to finish a thought that Daniel DeNoon brought up with possible sequel shedding, I don't think I got quite clear.  Is there any evidence yet as to whether it is shed by that route or not yet?  And I have a couple of others. 
Anne Schuchat: Sure.  We are looking at shedding, and I'm not aware of results yet about gastro intestinal shedding.  It's certainly a question we have, since that definitely can happen with viruses. 

Dave Daigle: Richard, what were your other questions? 

Richard Knox: And if so, is it being used to determine whether there have been wider spread than has been reported or maybe even asymptomatic spread.  And then finally, if I may, some have wondered whether we might see a summer flu phenomenon.  I think you just suggested that you think it is likely to follow the usual pattern in which temperature and humidity will suppress that.  But like Frank Monto suggested, maybe we will.  Can you talk a little bit about the possibilities of that? 

Anne Schuchat: We are very interested in the question of asymptomatic spread, and that's part of the evaluations that we're doing.  This can happen with seasonal influenza strains, and we are looking at that possibility, as well.  We're working towards development of a serologic assays that can tell us whether a lot of people have been exposed without getting clinical symptoms.  So that's another thing we'll be looking for.  We don't have results on that yet at this time.  We wonder whether this strain will continue during the summer, and give us more of a summer influenza pattern.  This is certainly a possibility.  It's not something that I can predict.  Most years, the seasonal influenza strains have very reduced circulation in the summer months here in the northern hemisphere.  Unfortunately, we don't yet know whether we'll going to get a break this summer with this virus.  We'll be looking there and we’ll also be looking in the southern hemisphere where we expect there may be an important increase of this virus. 

Dave Daigle: Thank you, Richard.  Next question, please, operator. 

Operator: The next is from Marilynn Marchone, "The Associated Press.” Your line is open.

Marilynn Marchone:  Hi, good afternoon. Thank you for doing this again.  I have a couple more questions that go along the lines of virulence of the virus.  And I'm wondering if, for instance, when West Nile virus emerged and we have new germs that have come up, you have done sero surveys or things like that to try to get a better handle on the attack rate.  You mention household surveys, and I'm wondering if there’s anymore general carriage studies that are under way, and also if anyone is collecting information on previous vaccination statuses, anyone who has become ill with swine flu. 

Anne Schuchat: There are active investigations beyond the household settings to understand transmission and asymptomatic infection.  The second question -- I just blanked on.  Could you repeat the second one again? 

Marilynn Marchone: If anyone is collecting information on previous flu shots, and anyone -- whether that theory about older people have some immunity perhaps through either natural exposure or previous vaccination? 

Anne Schuchat: Yes, thank you.  There are investigations that are looking at previous influenza vaccinations this past season, and whether there is any partial protection against this particular virus from the seasonal flu vaccine.  That would include different age groups to understand whether the patterns we're seeing in older persons who have a higher proportion of vaccine exposure -- you know, basically is what the vaccination is much more common among people over 65 than it is in the general population.  We don't think right now that the vaccination against seasonal flu provides protection.  But we will be looking at those data carefully as they continue to amass.  We don't think that's the explanation for the situation with seniors, but it's still a possibility and we'll complete those studies to look into that. 

Dave Daigle: Thank you, Marilynn.  Operator, we can take two more questions.

Operator: The next is from Rob Waters, "Bloomberg News".  Your line is open.

Rob Waters: Thanks very much.  Most of my questions have been answered, actually, but I did want to make sure about one fact.  The six cases, the six deaths, are those all confirmed, and can you tell me where they are?  What states they're from? 

Anne Schuchat: Yes, what I do is refer you to our website.  I believe our website just has five of the deaths listed.  It does include their geographic area.  This is WWW.CDC.GOV, and you can hit the spotlight for H1N1.  The sixth death that isn't yet on our website was announced by New York City.  So New York state is the sixth state.  This wouldn't be on our table. 

Dave Daigle: Thank you, Rob.  Next question, please, Operator. 

Operator: The next is from Sandra Young, CNN, your line is open. 

Sandra Young: Yes, hi, thanks for taking my call.  I'm wondering, there were about a thousand sick children at one New York City school, more than 200 at another.  And looking at the big picture at schools overall in the U.S., I'm wondering if these are big numbers.  In other words, are the H1N1 numbers higher at New York City schools than they are at other schools? 

Anne Schuchat: There are a number of schools around the country that are experiencing substantial outbreaks.  The majority of schools are not.  So we are aware that health departments are looking into outbreaks of influenza-like illness in schools within their jurisdictions.  And CDC is assisting in some of those efforts.  This is -- this -- we can see outbreaks in schools during seasonal -- the season of influenza.  That can sometimes happen.  I would say it's very unusual to have several outbreaks in schools this late in the year in multiple different states.  So this is another one of those unusual features of this novel influenza strain that we're seeing.  And it's certainly been a challenge for the communities, you know, to manage those problems. 

Dave Daigle: Thank you, Sandra and thanks to all of you for joining us today.  We don't have a briefing planned for tomorrow, but we can always put one together if need-be.  Thanks again.  Bye. 

End

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