Press Briefing Transcripts

Seasonal Flu Update

February 15, 2008

LISTEN to AUDIO

OPERATOR:  Good afternoon, and thank you all for holding.  Aa this time your lines have been placed on listen only until we open up for questions and answers. Please be advised today′s conference is being recorded. 

If you have any objections you may disconnect at this time.  I would now like to turn the call over to Dave Daigle.  Please go ahead, sir.

DAVE DAIGLE, CDC MEDIA RELATIONS:  Thank you, and I′m sorry.  We started a few minutes late to allow some more people to join. I′m Dave Daigle with CDC′s Division of Media Relations. In addition to publishing our weekly influenza surveillance report, we have published an early release MMWR today.

This updates influenza activity in the U.S. from September to February.  With me today is Dr. Joe Bresee, that is Dr. Joe Bresee, B-R-E-S-E-E. He is the Branch Chief in the branch of epidemiology and prevention of CDC′s influenza division and he′s going to update us on some aspects on the flu season and some other aspects that we′re finding so far this year.  Thank you.

DR. JOE BRESEE, BRANCH CHIEF, BRANCH OF EPIDEMIOLOGY AND PREVENTION, CDC INFLUENZA DIVISION:  Thanks, Dave.  This is Joe Bresee.  Hello, everybody.  Good afternoon.  Today I′m going to give you a quick update on the update of the influenza season and some other aspects of the influenza season as Dave had said.

After relatively low levels of influenza activity in the early part of the season, since January influenza activity has been picking up in the nation as I said last week.  This week 44 states are reporting widespread influenza activity.  This is up from 31 states reporting widespread activity last week.  Five states are reporting regional activity, making 49 states overall in one of our top two categories of activity.

Overall this week a third of specimens tested by the U.S. World Health Organization laboratories in the United States which is one of the ways that we track influenza activity, are reporting positive specimens, so one-third of the specimens tested for influenza are positive which has increased from last week′s total as well.

In addition, this week we will report ten child deaths have occurred from influenza during this season.  Nine of these deaths have occurred since January 1 and the increase coincides with the overall increase in influenza activity in the nation.

Surveillance information from this week indicates that the H3N2 virus, which again is one of the two A-type viruses, or A subtypes, is currently the virus that′s circulating most widely in the United States this week and has become the predominant virus in the country this year.

Finally I′ll finish by just saying that CDC would like to remind folks that – I′m sorry, CDC would like to remind people that they can still take additional measures besides vaccination, although vaccination remains the best method of prevention for influenza vaccine. 

We′d like to remind folks that other methods are available to prevent or treat the influenza, including protective – everyday protective actions like staying home from work when you′re sick and use of – appropriate use of antiviral medications.

That′s all I had as my short preamble, but I′m happy to answer questions about any parts of the report of the season that you have.

DAIGLE:  Thank you.  We′re ready for questions now.

OPERATOR:  Thank you.  At this time, if you would like to ask a question please press star one on your touch-tone phone. You′ll be prompted to record your name for proper registration.  To withdraw your request, you may press star two.  Again, to ask a question, please press star followed by one on your touch-tone phone. One moment for the first question.

Thank you.  Our first question comes from Jeremy Manier, Chicago Tribune.  Please go ahead.

JEREMY MANIER, CHICAGO TRIBUNE:  Thanks very much.  I just wanted to ask how unusual the child deaths are that you′re seeing. And also you may have also addressed this in the previous week, but the incidents of like chemical resistant H1N1.  Has that been seen before, resistance to Tamiflu and then the numbers that you′re seeing it now?

BRESEE:  Yes, both good questions, and thanks for asking, Jeremy. First, about the pediatric deaths. Pediatric deaths are tragic events. And we′ve monitored them – we have monitored them in the U.S. as one of the components of our surveillance for the past four years – that the numbers of deaths we′re seeing this year, ten so far this season, is not particularly unexpected, given the data that we have from the previous three or four seasons that we′ve looked at this.

Over the previous three or four seasons, to give you context, we′ve seen somewhere between 44 and 73 cases in the last three years of pediatric deaths attributable to influenza.  And so the finding of ten this late in the season is not totally unexpected.  However, the season′s not over yet and we′re still seeing increasing activity, and we may see more pediatric deaths before the season′s finished.

The second question you had is also nice to touch on as well. We had mentioned last week that some of the AH1N1 viruses this season in the United States and worldwide had been resistant, or been found to be resistant to Tamiflu, or oseltamivir, which is the most commonly-used antiviral agent.

We had reported last week, and I′ll update those numbers this week, that overall the influx of viruses that we′ve tested that have come from U.S. patients, 4.6 percent of those viruses are resistant to Tamiflu. 

If you just look at the viruses that we′ve tested that are of the subtype AH1N1 where all the resistance has occurred, that we found 8.1 percent of the viruses are resistant.  So less than 10 percent of the H1N1 viruses are resistant this week. And that compares reasonably the same with viruses worldwide, slightly higher rates of resistance in Europe, slightly lower in Asia.

We have seen this before, though not at this level. Previous to this year less than 1 percent of the viruses tested have been resistant to Tamiflu.  So this represents a real increase in resistance.  So far we don′t know if the resistance is likely to continue to increase or subside. And we′re monitoring it much more closely this year than we have in the past.

DAIGLE:  Thank you, Jeremy. Next question, please.

OPERATOR: Thank you. Our next question comes from David Brown, the Washington Post.  Please go ahead.

DAVID BROWN, THE WASHINGTON POST: Hi. Thanks. Dr. Bresee, if – have you calculated what fraction of the whole season′s tested and typed samples are of strains that are not in the current vaccine formulation, namely H3N2, Brisbane, or the Influenza B that′s, I forget what′s in it and what this newly emergent one is, but when you put those two together what fraction of the samples are of strains that are not covered by the vaccine?

BRESEE:  That′s a good question, David. Thanks for asking.  The truth to that answer is we get, as we do surveillance for viruses in the country, we get a fraction of the total viruses that are circulating in the country clearly, because we don′t test everybody for influenza.

And because we get a subset of viruses that are in the country, we don′t necessarily know that the, with precision at least, that the viruses that we look at in our lab represent perfectly everything that′s out there in the country.  

So the true answer to your question, what proportion of all the disease out there, all the viruses is likely to be caused by a strain that′s not well covered by the vaccine, we don′t know with accuracy. 

But we do know that the viruses that we have tested in our lab, which we think is a fairly good indicator of what′s circulating out there, we know this week′s numbers are that of 84 percent of the viruses that we tested are Influenza A viruses and 16 percent are Influenza B viruses.

If we assume, like I presented last week, the data I presented last week which are relatively unchanged this week, that most of the B′s are likely to be less well-covered by the vaccine than ideal matches. 

And of the A viruses, which again account for about 85 percent of the total, a little more than half of those are H3N2 viruses, which like I said last week, relatively poorly matched with the vaccine.

And so if you think about those numbers for a second, slightly more than half of the viruses that we are looking at in our lab are viruses that are somewhat different than the vaccines strains.  So it may not be well-covered by the vaccine strains.

But, again, the truth of the answer is we would expect that two of the three common circulating types or subtypes are not as well-covered by the vaccine as an ideal match this year.

DAIGLE:  Thank you, David.  Next question please.

OPERATOR:  Thank you.  Steven Smith, the Boston Globe, your line is now open.

STEVE SMITH, THE BOSTON GLOBE:  Hi.  Good afternoon, Dr. Bresee:  I′m wondering if you could tease apart the why here.  Certainly in New England we′re seeing substantially more influenza activity than we have in the past two or three seasons and as I understand it that′s reflected nationally.

So why is that?  Is there indication that the strain and circulation that there′s been either genetic shift or drift?  Is it a reflection of what you were just discussing vis-à-vis the relatively poor vaccination coverage?  In other words, why are we seeing so many more people flooding into PCP′s offices this season than we have in previous years?

BRESEE:  Yes, it′s a great question, Steve, and thanks for asking it.  The real answer to the question is, as you know, influenza seasons are variable.  We have some mild seasons, some more severe seasons.

In the last two or three years as you said before this season, we′ve had consecutive relatively mild seasons.  If you look at severity based on the number of deaths we expect to occur because of influenza, or the number of hospitalizations.

We′ve had a few relatively mild seasons in a row.  This season we are seeing more disease out there if you look at the map, and probably higher rates of hospitalizations and deaths than we we′ve seen in the last couple of – we might at the end of the season – in the last couple of years.

But I′ll say that, this season though we are having more disease, more widespread disease, right now than we have in the last couple of seasons, it is not an atypical season if you look back over the last 20 years.  If you look back over the last couple of decades of flu seasons, we do see seasons that look very much like this season, that have more hospitalizations, more mortality associated with them and just more widespread disease that occurs at the same time.

The reasons for that are probably multiple, but I think we can′t discount the fact that, in seasons where we have a predominant H3N2 a sub-type virus circulating, we tend to have more severe disease in those seasons and so what we′re seeing now may be the result of the shift from an H1 predominant season to an H3N2 virus.  But there are probably multiple reasons why we have bad flu years versus mild flu years.

DAIGLE:  Thank you Steven.  Next question please.

OPERATOR:  Thank you, Steven Lamm of  the Today Show, your line is now open.

STEVEN LAMM, THE TODAY SHOW:  Actually, the question was already answered on the coverage of our current vaccine, so thank you very much.

DAIGLE:  OK, thanks Steven .  Next question please.

OPERATOR:  Thank you, Helen Branswell, Canadian Press, your line is open.

HELEN BRANSWELL, CANADIAN PRESS:  Thanks for taking my question.  I haven′t seen the MMWR article yet so I may be asking you something you answered there.  But, did anybody, was anybody able to type the viruses that infected the children who died?  Do you know if they died from a mix of the sub-types or were they B deaths, H3N2 deaths, do you know?

BRESEE:  That′s a good question, Helen, thanks.  We′re the children who had been reported as having died associated with flu so far this year.  Those are still under investigation by the docs that took care of them.  So, we will have those data in summary during the season at some point in a summary, but I don′t have them right now.

DAIGLE:  Thanks Helen.  Next question, please.

OPERATOR:  Thank you.  Bob Roos, CIDRAP News, your line is now open.

BOB ROOS, CIDRAP NEWS:  Thank you.  Doctor Bresee, I was wondering with this – with the sub-optimal matches between the vaccine and circulating strains, have there been reports of – have there been many reports of cases in people who are vaccinated?

BRESEE:  Yes, it′s an excellent question and we have heard anecdotal reports, in the news and reported to CDC of people who have had influenza disease and severe disease that have been vaccinated.  We do every year and we′ll have to remind folks that influenza vaccine is – while it′s the best method to protect against influenza, it′s certainly not a perfect vaccine, even in the best years you can get vaccinated and get influenza still.  

But even in those year where the vaccine matches less well against circulating strains, we know that getting vaccinated will tend to make the illnesses milder, lessen the chances a person has a very severe outcome.  And so, we have heard about the cases that have been vaccinated, but that wouldn′t be atypical of any year.

DAIGLE:  Thanks very much, Bob.  Next question please.

OPERATOR:  Thank you, Mike Stobbe,  the Associated Press, your line is now open.

MIKE STOBBE, ASSOCIATED PRESS:  Thanks for taking the question.  So, to summarize, can we call it yet – is this a bad year for the flu or a mild year?  And I have a second question –

BRESEE:  That′s a great question Mike. I′ll tell you in May what the answer to that question is.  The designation, in my mind, of whether a year is severe, mild or moderate, I think, really I can only make at the end of the year when looking back. 

I think that we′re still seeing increasing disease in the country this year and whether that′s plateaued or going down next week or whether that continue to go up, will go a long way to making that assumption.  So, I promise to give you that answer later in the year.

STOBBE:  OK and on the H3N2 if in terms of what′s in the vaccine though, the Wisconsin, is it protective against this H3N2, the Brisbane?

BRESEE:  Thanks for asking the question.  We talked about that a little last week.  We know that the H3N2 strain in the vaccine that was Wisconsin-like virus has lower cross-reactivity against or probably less protection against the main H3N2 viruses circulating in the country right now, which we′ve called like A/Brisbane-like viruses in our communications last week.

And those viruses continue to predominate in the country, the A/Brisbane-like viruses, so we would expect that the H3N2 component of the vaccine might have lower protection against circulating strains.

We do have some very preliminary data from one of the CDC-sponsored evaluations of influenza vaccine effectiveness for this season that indicate that while the vaccine is likely to reduce the frequency of clinic visits in that population, which it did, the protection is probably likely to be lower than might be expected in a season when vaccine strains and circulating strains are well matched.

And so we do have some limited early field data that we′re still collecting to date and looking at and will make those estimates available very soon, but it looks like that, like we said with the vaccine match, that it′s likely to result in less well or less-than-ideal effectiveness that we may be seeing evidence of that.

DAIGLE:  Thank you very much, Mike.  Next question, please.

OPERATOR:  Thank you.  Richard Knox, National Public Radio, your line is now open.

RICHARD KNOX, NATIONAL PUBLIC RADIO:  Thanks very much.  Two quick things:  One, following up on Steven Smith′s question, we′re still thinking about why H3N2-predominant seasons are more severe, and secondly, I guess the FDA is going to advise the committee.  It′s going to make a decision next week about next season′s flu strains and vaccine flu strains, and I wonder whether it′s safe to say that Brisbane and Yamigata  are likely to be components of next year′s.

BRESEE:  Thanks very much, Richard.  I appreciate the question.  The answer, I don′t know why H3N2s are associated with more severe—there are lots of hypotheses for that.  Clearly, it′s evident if you look back over the last 20 or 25 years of influenza data in the United States that seasons in which H3N2 viruses predominate are generally associated with more deaths associated with pneumonia and influenza than seasons in which either H1 or B are the predominant viruses, so it′s certainly an observation that seems to hold up.  The reasons for it are probably multiple, and there′s many hypotheses, but it would probably take a longer conversation than we have now. 

The question about the vaccine strains is perfectly timely, and I thank you for asking it.  On February 14th, which was yesterday I guess, the World Health Organization Vaccine Strain Selection Group just announced the vaccine strains for the Northern Hemisphere that they would recommend, and it does include inclusion of the H3N2 Brisbane-like viruses circulating now, which also are already included in the Southern Hemisphere vaccine.  Those will be included in the next year′s vaccine for the—recommended to be included in next year′s vaccine for the Northern Hemisphere.  What the FDA will choose to put in the vaccines for the US will be made next week on the 21st at a meeting at FDA.

DAIGLE:  Thank you, Richard.  Next question, please.

OPERATOR:  John Sepulvado, Georgia Public Broadcasting, please go ahead.

JOHN SEPULVADO, GEORGIA PUBLIC BROADCASTING:  Hi.  I′m new to the story, so I′m just trying to understand.  I read a lot in the reports that the vaccine is “ineffective” or “less than effective.”  Can you just help me clarify and understand, is it effective?  Is it more effective than it′s been in years past, less effective?

BRESEE:  That′s an excellent question and you hit upon one of the difficulties of the influenza vaccine.  What we know about influenza vaccine, in ideal years, and those are years -- or ideal situations, and those are years when you vaccinate a group of people that are young and healthy and have good immune systems and you vaccinate them against a virus that they′re then exposed to during the season. 

In those years, we′d expect somewhere between 70 and 90 percent protection against influenza specific disease, and so if you think about that as a benchmark, what we find is that each year the effectiveness of the vaccine actually varies a bit, and it varies for multiple reasons.

It varies either because the vaccine, that the strains in the vaccine don′t perfectly match the strains that you′re exposed to in the environment.  It varies by age of the person sometimes, or by the health stance of the person sometimes, and so a lot of things go into determining how well the vaccine′s going to work each year.

This year, because we have two of the three types and subtypes that are present in the influenza vaccine this year that match relatively less well against what we′re exposed to in the environment, we would expect the vaccine, the efficacy, the 70 to 90 percent we talked about, to be a bit lower than that this year.

Again, we are doing studies on that.  We will have some data shortly, but we don′t have it yet, but again we′d expect a slightly reduced effectiveness of the vaccine this year, though we expect some effectiveness.

The other thing we know, and one of the clear messages is that even in years when the vaccine virus doesn′t match perfectly against the circulating strains, we do see some effectiveness, though it′s not 70-90 percent, it is some effectiveness, and this is particularly important in patients who have condition where they′re more likely to get severely ill with flu.

Those patients, even if you give them partial protection, they may be protected against hospitalizations. They may be protected against, death, and so it′s still very important to get vaccinated even in years where there is a less than ideal match against the circulating strains. 

DAIGLE:  Thank you, John.  Next question, please.

OPERATOR:  Thank you; Alison Young, Atlanta Journal Constitution, please go ahead.

ALISON YOUNG, ATLANTA JOURNAL CONSTITUTION:  Hi.  Thanks for taking my question. A few weeks ago CDC sent out an advisory for clinicians to be on the lookout for influenza co-infection with staph aureus in children, particularly relating to death.  Do you have any information about the deaths that you′re talking about today, how many of them may have involved staph co-infections?

BRESEE:  Yes, we do, Alison.  Thanks for the question. I′m just flipping through my pages, because I′d written that down before I came in the room and I will find it in two seconds.

Yes, we did issue a notice a couple of weeks ago that in the last flu season prior to this flu season we′d seen an increase in the numbers of pediatric influenza associated deaths that have also had an infection with a staph aureus infection as well, and we wanted the doctors to be on the lookout for that this year.

In the first ten cases that have been reported this season of influenza deaths, we have seen some of those cases have been reported also to have staph aureus co-infections like last year, and I will – later in this call I will get that information for you.

I can′t find it while I′m answering these questions.

DAIGLE: We apologize, Alison. I can follow up with you as well if we don′t find it before the end of the call.

BRESEE: Yes, thanks. I′m sorry about that, but we′ll get back to you very shortly.

DAIGLE: Next question, please.

OPERATOR:  Thank you; Delthia Ricks, Newsday, please go ahead.

DELTHIA RICKS, NEWSDAY:  My question already has been answered – well, I do have another one.  Can you explain a little bit about how the 122 hospital surveillance system works?  And what exactly you look for through that surveillance system?

BRESEE: Yes, that′s a great question. I love talking about that. I′m happy to. The 122 city system is a way that we monitor for pneumonia and influenza deaths in the United States, and we′ve done it for a long time, several decades.

And the way it works is in 122 cities around the country, and there′s a map on our website, thank you. There′s a map on our website.  In those, the death registrar, so the person who receives the death certificates each week in that city or that area, will report to CDC the total number of deaths that have occurred that week, and the number of those deaths that had either a pneumonia or an influenza written somewhere in their death certificate.

And what we know about those deaths over time is that pneumonia, the death certificates with one of those words written on the death certificate, tends to peak during influenza season.  And over time we′ve been able to do some statistical testing and can look at whether we think -- when we think influenza-associated deaths are peaking based on those death certificates.

And so on our website you′ll see curves that go up and down over the season.  And they help us know two things. One, when we think the nation is seeing influenza-associated mortality and when we think it′s going up. 
And second, a sense at least from year to year, of the severity of the season and will it be – we were asked earlier if we think this is going to be a severe season or a mild season.  One of the ways we make that designation at the end is by looking at those curves.

DAIGLE:  Thank you Delthia.  Next question please.

OPERATOR:  Thank you.  Carlotta Bradley, Associated Press, your line is now open.

CARLOTTA BRADLEY, ASSOCIATED PRESS:  Hi.  Can you hear me?

BRESEE: Yes.

DAIGLE: Yes we can.

BRADLEY: Can you break down, not necessarily by state or by numbers specifically, which regions are reporting more cases or that tend to be harder hit this year and are not being as hard hit?

BRESEE: Yes. If you look at the map the MMWR should be up any second now, but if you look at that map from the MMWR this week you′ll see that it looks almost the same color.  And so 44 states, I′m looking at my notes again, I apologize, 44 states this week are reporting widespread disease, which means to me – to answer your first question – that every region of the country is experiencing lots of flu right now.  They′ve experienced a lot of flu this week.

If you look at it another way we monitor influenza activity, which is by clinic visits.  We get clinicians around the country to report when they see influenza cases or influenza-like illness cases. 

If you look at those data, which are also presented in this week′s report, nine of the nine regions of the country, so every region of the country is reporting influenza-like illness above a seasonal baseline. And so right now this week, we′re seeing influenza activity in every region of the country.

DAIGLE: Thank you.  Next question please.

OPERATOR: Thank you. Tom Corwin, The Augusta Chronicle, please go ahead.

TOM CORWIN, THE AUGUSTA CHRONICLE:  Hi. Thanks for taking the call.  With the numbers that you′re seeing of Tamiflu-resistant influenza, can you clarify how concerning that is to you and whether or not that speaks to the need to develop more anti-virals?

BRESEE: I′m sorry, Tom. What was your first question?  I apologize.

CORWIN: Can you just sort of clarify for us just how concerned you are about the level of Tamiflu-resistant influenza you′re seeing?

BRESEE: OK. Got it, you know, that′s a great question.  We are certainly monitoring it very closely I would say.  The level of Tamiflu-resistance we′re seeing among this subtype of A-viruses, H1N1 is certainly higher than we′ve seen in the past, and we think it′s a real increase, and so for that reason we′ve enhanced surveillance in the country this year and all over the world to try to see whether this trend is going up or down.

At this point in the season, this point and what we know about it, the resistance levels are very low and so low at least that right now we′re not concerned enough that we would recommend different guidance on whether to take Tamiflu if you have flu or not, or whether or not to take it.

We think that the resistance level is sufficiently low right now that we wouldn′t change the policy, and so – but we are monitoring closely, and I think that over the next couple of months and next couple of years, if we see dramatic increases we may change our policy a little bit, but right now it′s still very, very low.

DAIGLE:  Thank you, and we have time for two more questions.

OPERATOR:  Thank you, our next question comes from Stephanie Harris, WAVY TV.

STEPHANIE HARRIS, WAVY TV:  Thanks for taking my call. First I wanted to kind of piggyback off of Alison if we don′t get that answer, and I′d love to know about more of the staph aureus.

We have another death that′s being investigated here in Virginia right now in a child, so I′m wondering, other than the staph, do you know of any other underlying health issues that any of these children may have had?

BRESEE:  We – I′ve got the update that I promised earlier.  Four of the ten cases that have been reported so far this year have also been reported to have had the staph aureus infection at the time of death, and so that′s the answer to the immediate question. 

The answer to the other question; we don′t talk about specific cases necessarily, of pediatric deaths and allow the states to do that.  We do know, thought, from previous data that children with certain underlying conditions, immune deficiencies, heart disease, lung disease, kidney disease and other things that are listed in our MMWR are more likely to get severely ill and probably more likely to die.

And so there are conditions that make it more likely to have severe influenza illness if you′re a kid, and that′s why – and being a kid makes it more likely to be hospitalized with influenza, more likely to be severely ill, and that′s why over the last few years we expanded vaccine recommendations to include vaccinating every kid from six months to five years of age because they′re all at higher risk for complications, and any kid below 18 years old that has one of these underlying conditions that make it more likely that they have severe disease.

DAIGLE:  Thank you, last question, please.

OPERATOR:  Thank you.  Our final question comes from Mark PicKard, WXIA Television.

MARK PICKARD (ph), WXIA TV:  Thank you, Dr. Bresee.  I was wondering, as you see reasonable percentage of the current influenza strains resistant to the available vaccine whether you′re getting any kind of an anxious flutter in your stomach that this might be a precursor to that pandemic that we′re apparently overdue for?

BRESEE:  No.  It′s a good question, Mark , and the answer is no.  A pandemic of influenza arises when a novel or completely new type of flu emerges in the population and then spreads easily from person to person.

The viruses we′re seeing in the country and in the world right now are viruses of types that are common in the human population, both in the U.S. and all over the world, and so these viruses won′t cause a pandemic.

It doesn′t mean, though, that these viruses are mild or innocuous.  Clearly we know that every year in influenza, people die of influenza in the country and a lot of people are hospitalized, and so the fact that – so the message is that it doesn′t have to be a pandemic to be a severe disease and to cause flutters in my stomach.

DAIGLE:  Thank you, Mark, and thank everybody for joining us today, and we should have the Flu View and the MMWR if they′re not up already up soon, as well as a transcript in a few hours of this call.  Thank again.

OPERATOR:  Thank you.  This does conclude today′s conference call. We thank you for your participation and you may now disconnect your lines.

END

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U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES