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CDC Telebriefing on Investigation of Human Cases of H1N1 Flu

May 20, 2009, 1 p.m. ET

 

Operator: At this time, your lines have been placed on listen only until we open up for questions and answers.  Please be advised that today's conference is recorded.  If you do have any objections, you may disconnect at this time. I would now like to turn the conference over to Mr. Tom Skinner. Please go ahead, sir.

Tom Skinner: Thank you, Lauren.  Thank you all for joining us today for this update on H1N1.  Today we have with us the deputy director of our influenza division, Dr. Dan Jernigan who will provide a brief update for you and then will open it up for questions.  Dr. Jernigan. 

Daniel Jernigan: Thanks a lot. The H1N1 influenza virus continues to circulate in the United States.  There are localized outbreaks that are ongoing in several states.  Those include Arizona, California, Illinois, New York, Texas, Washington, and Wisconsin that have reported the most activity so far.  There is on our website regional influenza activity that folks can go and look up.  In New York City and in surrounding areas, they are seeing increased levels of novel H1N1 influenza.  Some schools in New York, New Jersey and Connecticut are temporarily closing when there's evidence of unusually high and sustained number of flu-like illnesses.  The New York City health department is an incredible health department which has been working nonstop and they have noted through their own surveillance systems, some sharp increases in visits to the emergency departments for influenza-like illness.  In terms of the global cases, there have been reported to WHO over 10,000 confirmed cases in 41 countries.  In Mexico, there is ongoing transmission that overall possibly less activity being reported in some of those areas.  The total probable and confirmed cases in the United States continues to rise.  There are now reported eight fatalities.  Of the viruses that have been collected through the surveillance systems in the United States, most of those viruses, about 78 percent, are the novel H1N1 influenza. 

We know the known confirmed and probable cases represent, again, only a portion of the number of people that are infected or ill from the virus and, so, there is likely to be increased numbers of cases out in the community.  In the United States, as I mentioned, there were eight known fatalities.  There are 247 individuals that have been hospitalized and over 70 percent of those are- of those hospitalized patients- have had underlying chronic medical conditions, including pregnancy.  Asthma and heart disease are some of the most common.  So far, we know that individuals that are being hospitalized, many of them are receiving antibacterial therapy or treatment with antibiotics.  What we are seeing not as much of is the use of antivirals in individuals that are first being seen and being admitted with what suspected to be H1N1 influenza were suspected to be influenza, but, in addition, we do know that a number of the cases that have been hospitalized have presented with pneumonia and we want to be sure that those individuals do receive antivirals for pneumonia because that is one presentation that we're seeing in individuals with H1N1 hospitalizations. 

So far, the largest number of Novel H1N1 confirmed and probable cases, over 60 percent remain in the 5- to 24-year-olds.  Of those that are hospitalized, 40 percent are in the 19- to 49-year-olds.  So far, we continue to provide diagnostic kits to a number of countries around the globe and to many states.  44 of them are now able to do their own confirmations.  In terms of a vaccine, the production of seasonal flu vaccine is nearly complete and will be completed hopefully as planned.  Efforts to grow the candidate vaccines, viruses, for this Novel H1N1 vaccine are well under way.  We are at CDC hopeful that we will have vaccine viruses ready to send to manufacturers at the end of may and we're working to speed up the process as fast as possible.  As evidenced by recent state and city reports, H1N1 activity is likely to occur in different places at different times.  We expect that this may continue over the summer.  We're not quite sure what will happen in the fall, but we are being prepared for there to be an increase in the number of H1N1 cases later in the year.  At this point, I'll open up for questions.  Laura, we're ready for questions. 

Operator: Thank you, and at this time, if you would like to ask a question, please press star followed by 1 on your touch-tone phone.  Our first question comes from Robert Bazell, NBC News, please go ahead. 

Robert Bazell, NBC: Thank you very much.  I'm going to ask two questions.  We've heard repeatedly from health officials that this novel virus is at least somewhat more transmissible than most seasonal influenzas that you've seen.  What is that based on and does it make any difference whatsoever in terms of the public health recommendations that you would make?  And the second question is that, there's no question if you put a bunch of people, and some of them have influenza, into a confined space like a schoolroom, they're more likely to give it to each other.  The CDC had said earlier on that when you made the decision not to recommend school closures, that school closures does not affect the community transmission.  Is there any change in that perspective based on the more knowledge you've gained over time?  Thank you. 

Daniel Jernigan: Sir, let me address the second one.  I think the fact that you comment that the problem in the schools did not have any issue in the community.  I don't think that's exactly the case.  What we were saying is that transmission was occurring in the community and, therefore, the effectiveness of closing schools might not be as great.  So, I think it's not so much that we didn't think it would have an effect on the community. It's just that we were seeing transmission already occurring in the community and, therefore, one benefit for doing school closures was not met there. 
In terms of the amount of disease, what we would call the attack rate or the efficiency of the virus to go from one person to more than one person, that is spreading through community. Early on from Mexico and certain places in Mexico, there were some studies that did indicate that there was a very high attack rate, and that just means that any one individual was giving it to a whole lot more individuals and that the overall population was getting a lot of infection.  The more we look at it here in the United States, what we're seeing is the attack rates really coming in at about what we would see with seasonal influenza.  The household attack rates, that is what's occurring in terms of transmission within a household, is about the same as what we would see with seasonal influenza and the transmission within communities where we've been able to do those kinds of analyses indicate that they're right at about what we would expect for seasonal influenza, so that just means that we expect from a policy standpoint, we expect this to be spreading the same as we would see with seasonal influenza, but again, remember that a larger portion of the population may have absolutely no immunity or any protection for this one, which is different than what would happen through normal seasonal influenza.

Tom Skinner: Next question, Laura? 

Operator: Thank you. Our next question comes from Daniel DeNoon, WebMD. Please go ahead. 

Daniel DeNoon: Thanks for taking my question.  The World Health Organization's strategic advisory group yesterday put out their recommendations. And there was an interesting paragraph where they said older adults were shown to possess serum neutralizing antibodies to the new virus, most likely due to cross-immunity with human H1N1 viruses.  I didn't know that was an established fact.  Could you comment on that and tell me where -- about where they got that and whether that is, in fact, the case? 

Daniel Jernigan: Yeah, I think that information actually may be coming out this afternoon or tomorrow in an MMWR so, I actually may hold off on some of that information until tomorrow, but I think that comment probably was informed by some of the information that we were able to provide from some of the studies of serology or the studies of patients' blood.  And what that probably means is that the farther back you go in time, the more likely you are to have been exposed to H1N1 viruses back before 1957 and there's a possibility that having exposure to that virus many years ago may allow you to have some reaction to the new H1N1 that's now circulating and I believe that's where that comes from. 

Tom Skinner: Next question, Laura? 

Operator: Thank you, our next question comes from Helen Branswell, "The Canadian Press." 

Helen Branswell: Hi, if I could ask a couple of questions.  One's a follow-up to Daniel's.  I'm sorry, has it been determined whether or not any antibody is protective? 

Daniel Jernigan: That, of course, is the difficult issue.  When we look at serology, what we're seeing is the effect that somebody's blood has on the introduction of a virus into a cell, into a tube, essentially, and that is not something that tells you about protection.  The way that protection would be best evaluated, there are some more advanced kinds of studies that could be done, but generally, we look at the effect on the population and, so, at this point, we just don't have any of that information but based on the serology, the tests that we are able to do now, there's evidence of reactivity. And we can infer from that, to some degree, that there is some level of protection, but we don't have a good answer to that right now. 

Tom Skinner: Do you have a follow-up, Helen?

Helen Branswell: Yes, if I could, please.  When you were describing transmission rates and household transmission, et cetera, it just makes me wonder.  I mean, are people -- is anybody starting to wonder whether or not this is more like a case of antigenic shift than antigenic drift? 

Daniel Jernigan: I think, based on the availability of the studies we've looked at so far, a good proportion of the population has no immunity to it and, based on the distance, if you want to call it that, of this new H1N1 from the previously circulating seasonal H1N1, there's a very good distance.  It's a long way away.  And so while it may not be a different subtype, it is distant enough for us to be very concerned about its potential impact.  And so, in that sense, the drift versus shift is an ongoing discussion, but I think the distance between it and its nearest cousins is far enough that we're going to treat it in a way that we want to make sure that the most people are protected. 

Tom Skinner: Next question, Lauren. 

Operator: Our next question is from Todd Ackerman, "The Houston Chronicle." 

Todd Ackerman: Yeah, could you give more of an update on the vaccine efforts, particularly in light of the report out of the WHO meeting yesterday.  The virus was taking longer to grow than they'd hoped and it seemed like it would be long -- it would be later than previously predicted until they were able to start making the vaccine?  I guess, ultimately I'm kind of curious, what's the likelihood we wouldn't have a vaccine in the U.S. until later in the season than you would like? 

Daniel Jernigan: I think at this point, our best estimates are that we would have something for the fall.  As you know, from a lot of these discussions, there are many steps that have to come into alignment perfectly and at this point, we're moving along and have not had significant delays here in the U.S. with the development of the vaccine candidates.  We are very hopeful that we'll have those vaccine viruses ready to send by the end of May, which is something that we have been working on that timeline here for a while.  The -- there are many other steps and I -- you know, echo WHO's concern about the potential for there to be delays, but at this point, for the part of developing the vaccine candidates, we are hopeful that we'll have them by the end of May. 

Tom Skinner: Next question, please. 

Operator: Thank you, our next question comes from Betsy McKay, "The Wall Street Journal." 

Betsy McKay: Hi, thanks very much.  I have one follow-up to the earlier comments about exposure to H1N1 before 1957.  Is, just quickly, what is the significance of before 1957?  Is that, you know, related to the pandemic, if you could explain that a little more?  Secondly, I wanted to ask about to what extent are school-age children developing severe disease?  And I think you gave some data about number, percentage of hospitalizations, but I may have missed it, so what I'm wondering is how many, you know, how many school-age children are developing severe enough disease to end up in the hospital?


Daniel Jernigan: With regard to your second question, when we look at the number of cases that have been hospitalized, and for which we have enough data, there are 164 that we've done some analysis on, the median age, that is the sort of middle age of those folks that are being hospitalized, is 19 years.  And so, about 18 percent are 10 to 18 years old.  About 11 percent are 5 to 9 years old, so if you add those two together, you get the amount of school-aged children that are being hospitalized.  The largest number in terms of the percent of people being hospitalized is in the age range of 19 to 49 years old.  That's 37 percent.  But among those that are greater than or equal to 50 years, there's about 13 percent, and so, if we look at the overall numbers of cases, we're still seeing a significant number in the school-aged population.  The majority in the 19- to 49-year-old population but an increasing amount of greater than or equal to 50-year-old age group. 

With the H1N1 pandemic in the past, as many of you know, the H1N1 appeared in 1918 and through circulation around the globe each season, has drifted away from the original virus that appeared. And in 1957, that H1N1 was replaced by H2N2, with that pandemic at that point in 1957, so when we talk about the pre-'57 exposures, we're referring to those that had been exposed to the past H1N1 that went away in 1957. 

Tom Skinner: Next question.  Laura? 

Operator: Thank you, our next question comes from Mike Stobbe, Associated Press. 

Mike Stobbe: Hi, thanks for taking the call.  Doctor, two questions. First, I've heard some theorizing that you need three to six hours of exposure to an infected person to catch the novel swine flu.  Is that accurate?  And I have a follow-up. 

Daniel Jernigan: Okay, the reasons why someone becomes infected depend on many different factors.  The time within a room really is going to be dependent on how vigorously somebody is coughing that has infection, how much they're sneezing, what kind of contact you have with that individual, so to put an hour amount on it I think makes it difficult because there are so many variations in that. 

Mike Stobbe: Okay.  Thanks, and the follow-up, following up on Dan and Helen's and Betsy's question, I just want to be clear, are you saying right now that CDC's found evidence that there's a certain level of immunity in people, what would it be, 50 and older?  I don't want to get confused, because you were talking about rates going up in people 50 and older. 

Daniel Jernigan: Again, rather than dwell on that, I'm going to ask folks to follow up with the MMWR that will be coming out because it may state it in a much more eloquent way than I am, but let me just refer you to that because it will get into much greater detail about how those interpretations were arrived at. 

Tom Skinner: Next question please. 

Operator: Our next question comes from Richard Knox, National Public Radio. 
Richard Knox: Yes, hi.  Thanks very much.  Two things.  First, I'm a little confused about the relationship between the lack of population immunity to this virus and the fact that the attack rate so far, both in households and communities or schools, don't seem to be different from the regular seasonal flu.  Wouldn't you expect that lower or no immunity might lead to higher attack rates or am I getting something wrong?  And I'll ask a follow-up, please. 

Daniel Jernigan: Yeah, I think if you think of attack rates almost as the part of infection where it's going from one to another and the development of disease as being dependent on the host that receives that respiratory droplet, I think you can have a virus that has a high attack rate based on the fact that maybe it's replicating more frequently inside the nose of individuals that it causes people to sneeze more or whatever.  There are those factors that lead to the attack rate versus once somebody has been exposed, their ability to mount a response and, so, I think both of those play in here in that we have an attack rate that appears to be what we would see with seasonal but once somebody is infected, there may be a greater likelihood that they develop disease. 

Tom Skinner: What's your follow-up, Richard? 

Richard Knox: Yes, thank you.  I'm wondering why, if you have any information or hypotheses, that we would see so many more cases in Wisconsin and Illinois than in, you know, in California and New York, Arizona, and other places where you might expect it to be the hotspots?  Is there some factor there? 

Daniel Jernigan: That's right.  I think what we're seeing now, because we're looking very closely, is probably what happens each year with influenza in certain parts of the country have disease before other parts.  There may be certain factors or events where there are a number of people that are exposed, and so I believe what we're seeing now is a reflection of those factors and not necessarily a geographic or regional difference based on humidity or temperature or whatever. 

Tom Skinner: Next question, Laura. 

Operator: Thank you.  Our next question comes from David Brown "The Washington Post." 

David Brown: Yes, thanks.  I have two.  Would your advice to a -- to families and to clinicians be that if someone is sick with, you know, flu-like symptoms but is not in some sort of, you know, respiratory distress, that they not go to the emergency room, that they not go to the hospital or are you all still interested in people presenting and being diagnosed, to get a bigger sense of the, better sense of the size of the epidemic?  And my second question is, do you have any theories on why it's not -- in places in Europe, you know, UK and Spain in particular, where, presumably, the population in terms of its -- about the same? 

Daniel Jernigan: State your second question one more time. 

David Brown: Yes, the -- in industrialized populations in the UK and in Spain, which are presumably fairly similar to the United States in terms of general, you know, population, health, if the virus is not spreading but it is spreading here. Is there any theories on why that is? 

Daniel Jernigan: With regard to your second question, it may just really be a dose phenomena that in the United States, the numbers of people that have traveled to Mexico and have traveled to Mexico at a time many months ago, perhaps, where we've had more time for there to be transmission in the United States and more opportunities where people were exposed and, therefore, were able to give disease.  That's one thing.  Another thing is that we do a lot of testing in the United States that other countries may not be doing similar type of testing.  The -- in Europe and other places, it may be that the numbers of those that had traveled to Mexico and are able to, then, lead to transmission in Europe, that may be much lower.  Your first question had to do with individuals with mild disease and whether or not they should be going to the doctor.  At this point, we have recommended that if folks have symptoms, if they certainly do separate themselves from others by staying home.  Parents should keep kids home so that they're not transmitting infection at work or at school.  We've not had any recommendation that tries to have parents triage children to stay home or triage themselves to stay home based on a symptom complex, but are, instead, asking that folks, as they normally would, talk with their doctors and see about the need for coming into the clinic. 
Tom Skinner: Next question, Laura? 

Operator: Thank you, or next question comes from Caleb Hellerman, CNN. 
Caleb Hellerman: Hi, thanks for taking the question.  It has to do with the production of vaccines.  I wanted to know just to clarify, you've not yet received any candidate vaccines to be tested and secondly, you mentioned testing taken to speed up the process or make it as fast as possible, you know, what, if anything, unusual are you doing in that regard? 

Daniel Jernigan: At this point in terms of one of the steps that is of receiving and doing what's called safety testing, we are anticipating receiving some of the candidate vaccines very, very soon.  And so, excuse me, candidate viruses very, very soon.  And so, in that sense, thanks are moving forward.  There are processes that can be done in parallel so that once information from one set of studies is done, the others are already in play or have completed and, therefore, the full picture does not need to go necessarily sequentially and we're able to get some of that information in parallel. 

Tom Skinner: Next question, please. 

Operator: Our next question comes from Donald McNeil, "The New York Times."

Donald McNeil: Hi, thanks.  Can you give a little more detail about the serology test you started to describe there, something about something passing into a tube and --

Daniel Jernigan: Some of this will, again, be described in the MMWR tomorrow, but it's a test where we're able to take somebody's blood.  The blood is spun down so that only the serum remains and then you can take that serum and test it to see if there are antibodies that are in the serum that responds to different viruses that are essentially challenged in the test.  And so, it's a way of seeing whether or not somebody had been exposed to something similar in the past.  Again, I think tomorrow's MMWR will be much more eloquent. 

Tom Skinner: Next question, please. 

Operator: Thank you, our next question comes from Bob Roos, CIDRAP News. 
Bob Roos: Thank you for taking the question.  In that report from the WHO working group yesterday, they talked about a much higher estimate of possible H1N1 vaccine production.  They were talking about 4.9 billion doses and there's reference to or allusion to adjuvants and I just wondered if you had any insight of why they gave this much higher estimate from what we’re heard in the past of how many doses might be produced globally in a year. 

Daniel Jernigan: Right. Actually I was not at those meetings so I cannot comment about the numbers that were generated from that. 
Tom Skinner: Next question please.

Operator: Our next question comes from Jen Skerritt, "Winnepeg Free Press."  Please go ahead.

Jen Skerritt: Thanks for taking my question. Actually, I have two questions. I'm wondering if there's any concern that a vaccine may not protect against the virus if it mutates and whether there's any indication to date that the virus has mutated? 

Daniel Jernigan: So far, with the viruses that have been evaluated, and I believe we have 500 or so that have been sequenced, but of those we're not finding any significant divergence genetically.  We will continue to monitor that.  What you're referring to is whether we choose one of those viruses, make it into a vaccine, is there a likelihood that the virus that circulates through the summer and reappears, whether or not that virus might be different by the time we get the vaccine available.  The answer is: that is a possibility.  That's a possibility each year with influenza and, for that reason, we monitor the viruses very closely and we also monitor the effectiveness of the vaccine in people throughout the season as well and we are ramping up to be able to do both those things throughout this coming season.  At this point, we don't have any viruses that would suggest that the vaccine candidates would have a mismatch. 

Tom Skinner: Next question, please. 

Operator: Thank you, our next question comes from Michael Horowitz, WNBC-TV. 

Michael Horowitz: Thank you.  Does the CDC have any policy or any, make any recommendation about schools being closed that have suspected swine flu patients?  And, further, is there a policy or do they make any recommendation about schools that have confirmed swine flu cases? 

Daniel Jernigan: The best thing to do is actually to go to the website, there's actually a document there that addresses a lot of these issues.  And so, at this point, the guidance is that if there are for administrative reasons the need to close, that certainly is a local decision and that the guidance currently is very permissive for there to be local decision making and flexibility. 

Tom Skinner: Laura, we'll take two more questions, please. 

Operator: Thank you.  Our next question comes from Michele Merrill, "Hospital Employee Health Newsletter."  Please go ahead. 

Michele Merrill: Thank you very much for taking my questions.  I actually have two questions.  The first relates to the issue of the vaccine.  I'm wondering, typically, hospitals vaccinate their employees in their campaigns usually really in earnest in October and I'm wondering if you're going to be asking them to vaccinate early so they could vaccinate again if you had another vaccine for this H1N1.  And my second question is, just to get an update on what you might know about health care workers who have confirmed or suspected cases and how those might have been transmitted. 

Daniel Jernigan: Yeah, I think you raise a couple of very important questions.  The first regarding when to vaccinate and at this point, when to vaccinate is going to be driven largely by when it's available.  And so, there is a routine for production of vaccine and the preparation of it, the distribution of it, and then, of course, the campaigns that occur where those start often in October.  If possible, we do want to try and have an earlier rollout of the seasonal influenza vaccine simply for that reason to make it easier for an additional vaccine, if that's the ultimate policy.  And so, for that reason, we will be working very closely with manufacturers and with the multiple advisory committees through the federal government and with other partners to make sure that what is recommended in terms of timing is feasible and can be initiated to offer the most protection to the most folks. 

In terms of health care providers, we have presented that sum in the past.  I don't actually have the exact numbers with me now about how many have been infected.  I think it's upwards of 100, but I'll have to actually look at that, but the main point is that what we're seeing is a problem with what many call administrative controls, whereby there are policies within facilities that allow people to or that recommend people to use canned hygiene and to stay home when they're sick. And what we're finding is that the folks that are getting influenza at the workplace and health care facilities, many of them have been exposed to other workers who have come in sick, and so, this is something that is easily addressed through some of these types of activities that health care facility administration can promote and recommend and that is that if folks are sick, they should stay home, not only to protect patients, but also, to protect other health care workers from getting ill as well. 

Tom Skinner: All right, we'll take one last set of questions.  Please. 

Operator: Our final question comes from Alyson Wykoff, AAP News. 

Alyson Wykoff: Thank you.  Can you comment on the effectiveness of the antivirals so far, especially in children, and if you've seen any potential problems or adverse events? 

Daniel Jernigan: At this point, there are a number of individuals and different federal agencies that are using existing systems for monitoring adverse events due to antiviral drugs.  We, at this point, do not have anything that leads us to believe that there's increased levels of adverse events.  The numbers of young children that are getting treated, we're following that to some degree but we don't have those numbers now to say exactly what the antiviral effectiveness is for that population.  In the past, for seasonal influenza, some of that information is there, but our systems for collecting that information just don't have the numbers at this point to make any age-specification of what's happening with their antiviral effectiveness. 

Tom Skinner: Thanks, Laura, and thank you all for joining us.  We'll keep you posted each day of our plans to have daily media briefings and continue to go to our website, www.cdc.gov for the latest information as well.  Thank you for joining us. 

Operator: Thank you. This does conclude today's conference call.  We thank you for your participation.  You may now disconnect your lines. 

End

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