Press Briefing Transcript

CDC Telebriefing: Influenza A (H3N2) Variant Virus

Friday, August 3, 2012, Noon ET

• Audio recording (MP3, 12.3MB)

OPERATOR: Good morning and thank you all for standing by.  This is the conference coordinator.  All lines will be placed on listen only mode until we're ready for the question and answer session.  This call is being recorded.  If you do have any objections, please disconnect at this time.  I would now like to introduce your speaker, Mr. Tom Skinner.  You may begin, sir.  Thank you. 

TOM SKINNER: Thank you Laurie and thank you all for joining us today.  CDC is going to provide an update on domestic influenza A H3N2 variant infections in humans.  With us today is Dr. Joseph Bresee, a medical epidemiologist in our influenza division at CDC.  His last name is spelled b-r-e-s-e-e.  Dr. Bresee's going to provide a three to five-minute overview and then we'll get to your questions and answers.  Also joining us today is Dr. Lisa Ferguson.  That's spelled f-e-r-g-u-s-o-n.  She is a veterinarian in the National Animal Health Policy Program office at the United States Department of Agriculture.  She will be available to help answer questions when we get to the Q and A.  I’m going to turn it over to Dr. Bresee at this time. 

JOE BRESEE: Thanks, Tom.  Hello, everybody.  This is Joe Bresee at the flu division at CDC. Today I’m going to give you a quick update on an increase in the number of cases of influenza A H3N2 variant virus because on August 3rd, today, CDC’s FluView U.S. weekly influenza surveillance report, announced 12 new cases of H3N2 variant virus infection from three different states: Hawaii, Indiana and Ohio.  The virus was first detected in humans late last summer, July of 2011 and since July 12th, 2011, there have been 29 total cases of H3N2 variant virus infection detected, including the 16 cases occurring in the last three weeks.  Twenty-nine cases of infection with this H3N2 virus since the fall of 2011 is a significant increase in the number of detections for these types of virus we've seen in recent years.  All 29 cases were infected with H3N2v viruses that contain the matrix or M gene from the influenza A H1 pandemic virus.  This M gene may confirm increased transmissibility to and among humans compared with other variant influenza viruses. 

Before I summarize or further summarize the cases and the investigations underway, let me give you a brief background about these viruses to put things into context.  So like humans, influenza A virus infections are common in pigs but influenza viruses that commonly spread among pigs are generally different than the viruses that are common in humans. Occasionally humans can be infected with swine influenza viruses usually when in close contact with infected swine.  Similarly, human influenza viruses can be transmitted sometimes from ill humans to pigs.  It's important to note that swine influenza viruses have not been shown to be transmissible to people through eating or proper handling of pork or pig meat or other products derived from pigs.  It's not a food borne disease.  When people are infected with influenza A viruses that are known to be genetically similar to viruses circulating in swine, these viruses are called variant viruses.  From 2007 when novel influenza viruses such as variant viruses became a nationally notifiable disease through 2010, one to six such viruses were reported to CDC each year.

 So a summary of the recent cases.  Each of the recent 16 H3N2 variant cases reported in the last few weeks reported contact with swine prior to their illness onset.  In 15 of these cases contact occurred while attending or exhibiting swine at agricultural fairs.  All cases have been laboratory confirmed at CDC.  While no human-to-human spread has been identified in recent cases, limited transmission from person to person is thought to have occurred on three occasions in the fall and winter of 2011.  Importantly, sustained efficient community transmission of this virus, H3N2v virus has not been detected to date.  Clinical symptoms of the H3N2 virus infections have been generally consistent with symptoms associated with seasonal influenza virus, such as fever, cough, sore throat, muscle aches and headache.  No hospitalizations or deaths have occurred from the 16 confirmed cases but three cases were hospitalized among those detected last year in 2011.  All of those hospitalizations occurred among people with underlying diseases that put them at high risk for severe influenza infection.  Of the 16 recent cases, 13 of the cases are among children and three are among adults.  This is similar to the ages of the cases in 2011 and early 2012 that comprise the whole 29 and it actually is consistent with data from research studies that indicate that children may be more susceptible to the infection than adults.

So what to do.  Because most cases have occurred among persons who have had contact with swine in the setting of agricultural fairs, special attention is being paid to preventing transmission in these settings as many fairs are ongoing now or soon will be underway.  CDC’s detailed guidance for preventing infections in these settings is posted on CDC’s website. Key messages include wash your hands with soap and water before and after exposure to animals.  Avoid drinking, eating, or putting things in your mouth while in animal areas.  Don't take food or drink into animal areas.  If you have a condition that puts you at high risk for serious complications from influenza such as lung disease or diabetes, consider avoiding exposure to pigs in swine barns this summer altogether especially if sick pigs have been identified.  Avoid close contact with animals that look or act ill when possible.  If you develop flu symptoms following direct or close contact with swine and you see your medical provider, tell the doctor about this exposure.  They can advise if testing or treatment is appropriate.  Medications that have been effective in treating and preventing seasonal influenza infections are also likely to be effective in treating these variant virus infections. 

CDC, along with state and local health departments and our colleagues in animal health will continue to monitor for these cases and provide information on how to prevent them.  Because influenza viruses are always evolving, we will watch closely for signs that the virus has gained an increased capacity for efficient and sustained human-to-human transmission.  Thus far we have not seen this type of transmission and therefore are not seeing features consistent with the earlier influenza pandemic.  Even so, the H3N2 variant virus vaccine has been prepared or the candidate has been prepared in clinical trials are being planned for this year.  So in summary, while sporadic cases of this variant virus have been observed for many years -- variant viruses have been observed for many years, we've detected cases of this variant virus with increasing frequency over the last year, particularly in the last month.  We expect that additional cases of human infection with H3N2v virus will be identified either from contact with infected swine or through subsequent limited human-to-human spread, we also expect that some of the cases might be severe.  The CDC and USDA websites have guidance on protecting yourself and your families.  As we learn about these cases and this virus, we'll keep you updated.  Thanks very much. 

TOM SKINNER: Laurie, I think we're ready for questions, please. 

OPERATOR: Thank you, sir.  At this time if you would like to ask a question, please press star 1.  You will be prompted to record your name.  Press star 1 to ask a question.  Press star 2 to withdraw your request.  One moment for the first question.  Our first question comes from Miriam Falco with CNN Medical News Atlanta. 

MIRIAM FALCO: Hi.  This is a question for the veterinarian.  A, how do you identify an animal as being sick, the pig? And then for Dr. Bresee, if you can clarify again, there's no distinction or are there distinctions between regular flu and this particular flu when it comes to I’m sick?  Not necessarily in the DNA but the symptoms wise.  How would somebody suspect that they had this one as opposed to the other kind of flu’s that are out there? 

TOM SKINNER: Dr. Ferguson, you want to take the first question? 

LISA FERGUSON: Okay.  If I can attempt to clarify, are you looking for what should somebody look for when they're looking at a pig, what should they be looking for, or are you looking at how do we diagnose swine flu in pigs? 

MIRIAM FALCO: Yes, I’m asking from the consumer level.  If you're telling people they're supposed to avoid contact with sick animals, how do people know that?  I mean, if I’m a farmer, I would probably know that.  If I’m somebody at a fair I would not.  I wouldn't personally.  So I’m just -- I’m not talking about in the lab, I’m talking about in practical. 

LISA FERGUSON: Yes.  Thank you.  That's what I assumed but I just wanted to make sure.  So pigs actually in many ways respond to flu viruses very similar to people.  And sometimes actually in pigs the clinical signs are generally fairly mild but they are often respiratory type signs.  So if you see a pig that has a runny nose, that is coughing, they've got goop in their eyes, they're standing away from the rest of the pigs in the group, that would be a pig that looks sick. 

MIRIAM FALCO: Okay.  Are there any other animals that are at risk for this?  Any other mammals aside from humans- that you know of? 

LISA FERGUSON: We have identified this strain of virus in swine and that's it.  We identify other influenza viruses, I think you're familiar with avian influenza, so there are influenza viruses in birds.  There have been some other strains in seals and you can have strains of flu in dogs and in horses but they are generally different.  There are other strains other than this H3N2. 

MIRIAM FALCO: Thank you. 

JOE BRESEE: This is Joe Bresee.  I’m happy to answer the second question.  It's a good question.  In fact, you can't.  Folks infected with the H3N2 variant virus have very similar symptoms and signs of their illness compared with people infected with normal human seasonal viruses.  They tend to get respiratory illness, they tend to get cough, sore throat, muscle aches, headaches.  They tend to have self-resolving illnesses like with seasonal flu.  They can be severe illnesses like seasonal flu, especially if you have underlying medical conditions that predispose you to severe illnesses with flu.  So based on clinical symptoms alone, they really are difficult or impossible to tell apart.  That's why we're advising folks if you have contact with swine and then you get sick, it's good to talk to your doctor and maybe be tested for this virus because I think the exposure variable knowing that you're exposed to a pig may be the one differentiating thing you can think about.  Ultimately testing using a test that we do here at CDC and some state health departments can do is the way to differentiate these two diseases. 

OPERATOR: Thank you.  Our next question comes from Mike Stobbe with the Associated Press. 

MIKE STOBBE: Hi.  Thank you for taking my question.  Actually, two.  The first one's just confirming numbers.  Dr. Bresee, did you say 16 cases in the last three weeks but that includes 12 that were confirmed just this week?  And then my second question was of those cases, 10 were at this fair in southwestern Ohio or they've been linked to that fair, the Butler county fair.  Was there something -- what was going on at the Butler county fair?  Did a lot of people have contact with a particular pig or was there some unusual type of contact there?  Any clarification on why we got so many cases out of that one situation? 

JOE BRESEE: Yeah, Mike.  Good question.  First, yeah, you're right.  Twelve cases are confirmed this week and they are part of that 16 cases that have been confirmed in the last three weeks.  Your numbers are correct.  The investigation's underway with the Ohio county fair that yielded these cases.  I think the -- clearly the usual risk factors at play in these infections were close contact with the pig, but the exact risk factors associated with these cases and the fair I think will be investigated over the next week or two by the Ohio state health department and Butler county health department. 

TOM SKINNER: Mike, did you have a follow-up question? 

MIKE STOBBE: No.  Those are the two, Thanks. 

TOM SKINNER: Okay.  Next question, Laurie. 

OPERATOR: Thank you.  The next question comes from Daniel DeNoon with WebMD. 

Daniel DeNoon:  Thanks for taking my question. Dr. Bresee, would the seasonal flu vaccine have a component, the H3N2 component be protective against this kind of flu and can you talk to me about what is different about this strain of flu that -- from the seasonal H3N2?  Thank you. 

JOE BRESEE: Yeah, good question.  So while the seasonal influenza vaccine has an H3N2 component in the vaccine every year, that H3 component is substantially different than the H3 viruses we're talking about today. So the seasonal viruses likely won't have protection against this virus.  We definitely want people to get vaccinated with the season's virus because flu's right around the corner. But it’s not a way to prevent infection with this virus.  The differences between this virus and the seasonal virus and the thing that has us interested and concerned about this are what we're seeing really.  We're seeing this virus compared to other swine viruses, seeing more cases, more clusters and the clusters that we're seeing are larger. And so we want to understand why we're seeing more cases of this virus now than we have in the past.  So those are parts of the initial investigation. 

I think the differences between this virus and seasonal virus is besides the virus themselves are that this virus doesn't spread efficiently in humans like seasonal virus does.  Seasonal influenza viruses we see every year are well-adapted to humans.  They grow well and are spread well between humans.  These viruses are for all intensive purposes animal viruses so they're not -- they don't do well in humans.  So we can get an infection with them and maybe we can pass it on to one or two folks, but they don't yet have the ability to spread efficiently between humans and therefore aren't human viruses yet.  That's the principal difference.  As we think about the viruses and learn about them over the next few weeks and few months, I think what we're really going to be looking for is evidence that the virus has made that change to be -- to be transmitting efficiently in humans.  So far we haven't seen that. 

Daniel DeNoon:   Might I just follow up by asking about the vaccine you've developed.  Can you give us more details about what you've done and what the clinical development program is? 

JOE BRESEE: I can't give you too many details because I’m probably not the person to give you the details.  We can get more details up on our website and we can communicate with you offline but it's a virus-- it’s a virus vaccine candidate that's made from one of these H3N2 variant viruses, very closely related to the viruses that we're seeing in these humans right now.  The candidate's been developed by CDC and through the usual pathway for vaccine development has now been shared with clinical partners who have developed clinical pilot lots of the vaccine and will start clinical trials to look at the safety and immune response to the vaccine in the next few months. 

TOM SKINNER: Ok, next question, Laurie. 

OPERATOR: Our next question comes from Elizabeth Weise with USA Today.

Elizabeth Weise: Hi.  Thanks for taking my call.  So it sounds like what you're saying is that while the thing you're concerned about is that this virus might become easily transmissible between humans, what you think might have happened is that we're looking at a swine virus that has somehow evolved to become more easily transmissible to humans?  I mean, because I know that there are always viruses circulating in the swine population, so what's different about this one?  Why is it suddenly popping up?  And are we seeing these cases, do you think, because this is primetime for county fairs or because this virus has evolved in a new and more disturbing way? 

JOE BRESEE: Those are great questions.  And I think you're right in your conclusion.  Let me just say that I think that this virus is a bit different than previous swine viruses because it has acquired this genetic material from the pandemic H1 virus, the M gene that we think might confer an advantage in terms of effecting humans and maybe even spread among humans.  And we think that not only because of what the M gene does in a cell but more because what we're seeing, these larger clusters and more cases than we had seen in previous swine -- with previous swine viruses.  So I think we're seeing evidence that this virus may be different because we're seeing more cases.  Whether it's due to the genetic makeup of the virus or whether it's due to the fact that we're looking more -- we're more likely to find more viruses when we're looking more or because we're seeing more interaction between humans and sick pigs I don't know. 

I think those will all be part of the investigations that will go on in the next couple of weeks.  I think we're seeing them now clearly because this is the season when we see county fairs and we see lots of humans and pigs close to each other, especially kids and pigs close to each other.  So I think that’s why we're seeing a spike right now. I think there probably is something different about this virus.  I think the take home message is this virus is still principally a swine virus and so when it infects humans it can cause illness but it doesn't seem to have onward spread from that human.  I think that's the key message.  It may be a little different, but it's still not a human virus and, therefore, we don't worry about it the same way we do as a human virus or early pandemic virus. 

TOM SKINNER: Beth, Do you have a follow up? 

Elizabeth Weise: No, that's fine.  Thanks. 

TOM SKINNER: Next question, Laurie? 

OPERATOR: Our next -- our next question comes from Bob Roos with CIDRAP News. 

Bob ROOS:  Hi.  Thanks for taking my question.  I just wanted to find out a little bit more about the candidate vaccine.  Do you have any idea how soon that vaccine might become available if it were needed and what would be the trigger for actually making that available? 

JOE BRESEE: I don't know those details, but I -- but we can certainly get them to you offline.  I think the trigger for going forward with vaccine production clearly is more evidence that an A virus like this virus represents a pandemic threat.  We're clearly not there yet and so that's all I can say, but I think that we can get more information about the vaccine development process for you, it's just not me that's the right person to give it to you. 

Bob Roos:  Thank you. 

TOM SKINNER: Next question, Laurie. 

OPERATOR: Thank you.  Our next question comes from Timothy Martin, Wall Street Journal.

Timothy MARTIN: Hi, everyone.  Can you guys lay out, one, I think there was a nod at the end of Dr. Bresee's comments about a forecast of future -- what the numbers might look like or what the severity of this virus spreading might look like.  That's question one.  If you could sort of clarify that forecast.  Two, could you talk -- what has history told us about how the swine flu’s tend to evolve over time?  There's been a clustering or larger than normal clustering of these viruses but what can we take from what's happened before?  Thank you. 

JOE BRESEE: This is Joe.  I’m happy to answer the first question and see maybe if Lisa wants to talk about swine influenza viruses generally for the second part of the question.  I did say that we would fully expect additional cases and even some severe cases.  That's based on the fact that there is this virus circulating in pig populations and there are interactions between accessible humans to these pigs.  As long as that happens we're likely to see additional cases.  We'll try to prevent those clearly with good hygiene, staying away from sick pigs, some of the core public messages we're putting out, along with our agriculture colleagues.  Even so we wouldn't be surprised if there were some kids or adults infected.  And, again, just because some people are prone to severe disease, we might see some severe disease in the future. So, that’s not surprising.  I think during the agricultural fair season there may be more of those interactions than in other parts of the year so we're likely to see additional cases in the next few weeks I would suspect.  I’m not predicting anything; I’m just projecting what we might see.  Lisa, do you want to talk about swine virus? 

LISA FERGUSON: Sure.  So influenza and swine, actually it's a fairly common swine disease and has been recognized to be out there for many, many years and producers generally deal with it.  As I said earlier, often times it's a relatively mild disease in swine.  Over the past few years, however, we recognize that things are changing and we've partnered both with our public health colleagues and with our state and industry colleagues to make a more concerted effort to see what flu viruses are out there in swine and how they're evolving so we've really started our surveillance efforts in earnest over the past couple of years and are laying the groundwork to see what's going on out there.  Since 2010 we've tested over 11,500 samples with about 1400 cases with positive results. And have sequenced many of them.  We haven't sequenced all of them yet.  Much of that is in progress.  So we know what strains we’re commonly seeing and are, as I said earlier, working with both our public health and industry colleagues to see what info we can glean from that.  We want to make sure that we keep track of how that virus is changing out there and what's happening.  We want to make available the isolates that we have for research and to just add to the general knowledge and more importantly from the animal health side we want to make sure that just as on the human health side, we have the appropriate diagnostic reagents and assays out there and vaccine products for the viruses that are occurring. 

Timothy MARTIN: So I can assume that those 11,500 are samples taken from people who have gotten sick from having close contact with swine or pigs, I mean? 

LISA FERGUSON: No, those are from pigs. 

TIMOTHY MARTIN: I see.  Okay. 

LISA FERGUSON: Sorry if I didn't make that clear. 

TIMOTHY MARTIN: Okay.  I guess what I’m -- just one quick follow-up, which is I guess what's unclear to me still is as you guys have studied more sample work from -- taken from pigs, do these types of viruses tend to pop up and disappear or -- I guess that's why I asked sort of a tracking question of, you know, if there's an expectation that this eventually could evolve in such a way that it would pass more easily from humans to humans, what's the time frame on that or could this go -- I just don't want to overplay this or pump this up into something it's not. 

LISA FERGUSON: So are you asking if in swine the viruses that occur in pigs, if they kind of crop up and then go away? 

TIMOTHY MARTIN: Well, both and then also with humans.  You know, you guys are going to closely be monitoring, you know, does the virus evolve in such a way that it will pass more readily and easily among humans.  What's -- how long might that take for the virus to evolve or is there no timetable? 

LISA FERGUSON: I can provide a little bit of info on the swine side but then I'll let Dr. Bresee see what he can do with the human health end of that.  Just as an example with the sequenced information that we have and let's use the pandemic H1N1 virus as an example, you know, we saw more instances of that in the viruses that we've identified last year than we have this year, you know, so does that mean that that virus is fading in the swine population?  Could be.  I don't think we completely have all of that information.  We do see strains evolve and crop up and then disappear.  I can't tell you exactly on time frames. 

JOE BRESEE: Yeah, this is Joe again.  I completely agree.  It's a good question but, in fact, the principles are that flu viruses are variable and evolve and mutate in ways that are hard to predict.  So I think that the public health principle, the public goals are really to pay attention closely not only to the virus and see how it's evolving, how it's mutating, but also importantly to the humans it infects.  I think we'll know that it has acquired the ability to efficiently spread between humans when we observe that it's acquired the ability to efficiently spread in humans.  And whether it occurs next week or whether it occurs in 20 years I don't think any of us are smart enough to predict right now.  And so that's the reason I think when these cases pop up we first want to hear about them and we investigate them vigorously with our state and local health partners. 

TOM SKINNER: Okay.  Laurie, next question please. 

OPERATOR: Our next question comes from Rob Stein, NPR. 

ROB STEIN: Yeah, hi.  Thanks for taking my question.  Two questions.  One is you said 15 of the 16 people got infected from contact with pigs at agricultural fairs.  What about the 16th?  How did that person get infected?  And can you describe how serious the illnesses were from all of these cases? 

JOE BRESEE: Sure.  So the 16 cases, you're right, 15 likely were exposed in an agricultural fair.  The 16th was a farmer that had a pig farm and was probably exposed occupationally.  The 16 illnesses we're talking about were self-limited respiratory illnesses that all resolved.  There were no cases among the 16 that were hospitalized, for instance. 

ROB STEIN: I see.  Okay.  Of the 29 cases you've had reported so far, have --

JOE BRESEE: We've had 3 hospitalizations among those. 

ROB STEIN:  Any deaths? 

JOE BRESEE: No. 

ROB STEIN:  Okay.  Great.  Thanks very much. 

TOM SKINNER: Next question, Laurie. 

OPERATOR: Thank you.  Our next question comes from Mira Oberman, AFP. 

MIRA OBERMAN: Oh, hi there.  Thanks for taking the call.  I just had another question in terms of issues of reporting.  I know obviously there's no exact number on this, but if you've got 16 cases reporting, I’m guessing there's a lot more cases where people just don't even bother going to the doctor.  Doesn't sound like a very serious flu.  So I’m curious kind of what, you know, previous studies have shown to be if you've got this number of reported cases, what kind of estimate you might have on the ratio between reported and not reported.  How many more cases could there be out there and furthering that, why is it important for the public to see their doctors so that public health officials can follow these kinds of infections? 

JOE BRESEE: Yeah.  That's a great question.  It's not unlike seasonal flu where people get sick with a respiratory illness, get a cough, a fever maybe for a few days and a few of those people actually go to the doctor.  Even fewer of those get tested for flu.  For seasonal flu for every case we detect with a lab test there's a whole lot more out there that actually stick with the flu.  This flu is probably the same.  We certainly probably don't hear about everybody and those that do present doctors or hospitals, probably everyone's not test the.  I think at this point early in the investigation what we want to do is get more of those people to go to the doctor, get more people tested so we get a better feel for the scope of this outbreak.  I think early case findings, the more complete we are, the better we are in understanding the outbreak and understanding the risk factors in how to prevent it.  That's the space and time we're in right now.  I think we're never going to be able to detect every case of the disease that occurs in an outbreak nor should we try, but we just want to know enough about the cases to inform our prevention strategies.  But we don't have a way to estimate right now the total number of cases out there.  Just what we measure. 

MIRA OBERMAN: Okay.  Thanks a lot. 

TOM SKINNER: Laurie, we'll take two or three more questions.  Next question please. 

OPERATOR: Thank you.  Our next question comes from Michael Smith, Medpage Today. 

MICHAEL SMITH: Yeah, Dr. Bresee, two quick ones.  One quick one.  I’m just doing the calculation here.  29 cases reported, 16 in the last couple of weeks.  Does that mean 13 last year or how do the rest of them break down? 

JOE BRESEE: Yeah.  It's a little more complicated.  Twelve in 2011, one case was reported early in 2012 and then these latest 16. 

MICHAEL SMITH: Okay.  Thank you.  The other question is can you talk a little bit about the m gene and what role it plays in transmissibility?  Because we know that the pandemic flu is reasonably transmissible but didn't cause serious disease on the broad scale although some people were very ill.  What does it mean if this virus has somehow accumulated the M gene from the H1N1 virus? 

JOE BRESEE: That's a good question.  While we don't know every function an M gene plays in the replication cycle of a virus, we do know it's related to viral replication and viral release from the cell.  So we are concerned that with an M gene a virus acquires from a human virus, the H1N1 pandemic virus or a virus that has adapted to humans and spreads easily, the presence of the M gene in that virus may confer the potential for that virus to infect or spread between humans to a greater extent than an M gene from a swine virus or avian virus. But that’s about all we know, I think there are virologists listening on the phone that can talk to you much more about the M gene and I am happy to talk offline and link you with those guys.  The principle is that the M gene from a virus that has shown the ability to be adapted to humans is now in a virus that's coming from swine.  I think that gives us a little indication that it may happen more often and may be more likely to spread between humans. 

TOM SKINNER: Laurie, we'll take two more questions. 

OPERATOR: Our next question is from Miriam Falco of CNN Medical News, Atlanta. 

MIRIAM FALCO: Hi.  Thanks for taking another question.  So some of the recent cases were in Ohio, most of them, and Indiana, close by and then you've got Hawaii.  Are the -- you know, are these -- is a possible source the same herd of pigs?  Does that have any influence or is this independently popping up?  I mean, if it's in -- I’m just trying to wrap my head around how is this getting from you know the middle of America and then Hawaii. 

JOE BRESEE: Yeah, that's a very good question.  Lisa may wish to talk about swine surveillance and what they know about the spread of this virus.  I'll say that there's -- from the epidemiologic investigations we don't have a link between humans or pigs in Hawaii and humans and pigs in Indiana and Ohio yet.  Those angles are being looked at carefully but so far there's no epidemiologic link between those two, Hawaii and the other two states.  I don't know if Dr. Ferguson wants to add anything. 

LISA FERGUSON: Sure.  I'll add a couple of things.  The investigation is still ongoing so as we get more information, perhaps we can answer that question slightly better.  I'd have to say though that it's probably fairly unlikely that there was one swine herd that led to all of this especially the Hawaii one.  I do know we have seen this virus and H3N2 with the M gene first identified in summer of 2010 and then we've had samples essentially from 11 states that show that similar type of virus in that intervening time frame. 

MIRIAM FALCO: So are you saying then that not everybody who's gotten sick has the exact same mutated H3N2 swine flu? 

LISA FERGUSON: I was speaking of viruses that we have isolated from swine over that time frame.  I'll let Dr. Bresee address specifically on the human side. 

JOE BRESEE: Yeah.  The viruses that we've detected in humans so far since last year are very similar to each other and so virus to virus are not necessarily completely identical down to the -- down to the base pair of the DNA but they're very similar viruses. 

TOM SKINNER: Laurie.  We'll make this our last question please. 

OPERATOR: Our final question comes from Mike Stobbe of the Associated Press. 

MIKE STOBBE: Hi.  Thanks for letting me go again.  This is triggered by something Dr. Ferguson said.  She was talking about how many samples have been taken from swine in the last several years and it triggered a memory of discussions during the 2009 pandemic of concerns that we didn't have enough surveillance in animals of the H1N1.  I was wondering, do we know with this new variant strain how old it is and was it first detected in pigs or was it in humans?  I was just kind of wondering if we're seeing this because we've been looking harder since 2009.  I was wondering if you could give us that context. 

LISA FERGUSON:  Okay.  I think definitely, you know, as you noted, we have significantly increased our surveillance in swine since 2009, especially after a number since 2010.  Regarding this H3N2 with the matrix gene in it, as I noted a minute ago, we had first seen that virus in swine in late summer 2010.  Now whether it occurred out there prior to that, I don't know.  Clearly there is a factor of as you look a bit more you find things, but what I can say is that's when we first saw it in swine. 

TOM SKINNER: Laurie, this concludes our call.  Thanks to Dr. Bresee and Dr. Ferguson for joining us.  Reporters can call the CDC press office for more information.  That number is 404-639-3286.  During this call you should have received via e-mail a copy of the flu view report that Dr.  Bresee referenced in the beginning of his comments.  This report has additional information about the cases that he discussed so you should have that in your e-mail in box.  If you don't, you can again call 404-639-3286 to ask for a copy of that FluView report.  Thanks for joining us. 

OPERATOR: That concludes today's conference.  Thank you for your participation.  You may disconnect at this time.  

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U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES