CDC News Conference Transcript

Update on Avian Influenza

January 27, 2004

DR. GERBERDING: Thank you for joining us for this press briefing. This afternoon I'm going to be updating you on the avian influenza outbreak in Asia and clarifying some of the activities that CDC has undertaken.

I think the good news right now is that this year's H3N2 influenza outbreak here in the United States has largely subsided, but we do share the concern with our colleagues in Asia with the people there who are experiencing yet another serious respiratory virus problem there, particularly as it's affecting the poultry and the birds, but also because of the fact that several humans have also been infected and several have died.

In the United States, we do not have cases of avian influenza in chickens or any other bird at this point in time, and so far we have not experienced any human cases. So right now the risk here appears to be very low, but we are taking a number of steps because this could be a very serious problem if the epidemic in Asia is not contained.

Now, we know already that there are 10 confirmed cases of avian influenza in Asia. 7 of those are in Vietnam; 3 are in Thailand, and already 8 people have died. So this is a very serious problem.

Right now the virus does not appear to be efficiently transmitted from birds to humans, and it does not appear to be transmitted efficiently from one person to another. In fact, we have not documented that it's been transmitted from one person to another, but we know from previous situations involving avian influenza strains that occasionally a person-to-person transmission may occur, and these viruses are prone to evolve over time, so there's always the possibility that transmission could be more efficient. That's why we're taking this very seriously right now and doing everything that we can to make sure that we're offering the best possible support for the World Health Organization and others who are combating the problem in Asia, and also we're taking steps here at CDC.

Yesterday we activated the Director's Operation Center to coordinate this investigation in our support for the World Health Organization interventions. We have 6 CDC scientists in Vietnam right now. We also have other CDC personnel who are stationed in Asia who are contributing to some of the activities going on in several of the countries.

Now, there is no indication for a travel alert or advisory to Americans traveling to the areas that are affected right now, but it is important that people who travel to countries that have confirmed poultry cases, to avoid contact with poultry farms, to stay away from the markets where live animals are marketed for the food supply and to avoid contact with items or surfaces that may have been contaminated with excrement from an infected bird.

We are also alerting clinicians here in the United States to take a careful travel history of anyone presenting with influenza-like illness, and if an individual has traveled to regions of the country where this problem is occurring, it is important to culture their respiratory specimens to be sure that they don't have influenza, and if that information suggests that influenza A is present--and the CDC will be working with state and local laboratories to use special tests to determine whether the strain of influenza is H5 so that we would want to be having the earliest possible detection of such a situation.

We also are asking that people who've traveled to these parts of the world to remind their clinicians of their recent travel history if they present with any illness suggestive of flu or flu-like illness so that the clinician can be sure to order the appropriate laboratory tests and to be absolutely sure that there isn't a potential infection with one of these strains.

Again, I want to emphasize that right now it appears to be very unlikely, but we want to be very vigilant and we want to make sure that we're doing everything we can to detect any possibility of introduction here.

Our CDC laboratorians have been working very hard since this problem emerged. Our scientists are collaborating with two other laboratories and the World Health Organization to develop the seed virus strain for potential vaccine production. This involves engineering the virus so that we remove the part of the virus that causes lethality in chickens because the vaccine strains need to be grown in chicken eggs, and if that part of the virus is present, it's very difficult to accomplish this.

In addition, engineering the seed virus allows for safe handling in laboratories and reduces dramatically the chance of any potential exposure to humans or introduction of the vaccine strain into a bird or a bird population that could be susceptible and serve as the mechanism of spreading it. So these steps are taken to ensure the safety of the vaccine process as well as the efficiency of the process.

As has been reported already, the seed strain that was created from the last Hong Kong avian influenza virus is not a good match for this year's strain, so we really have had to start from scratch and work to--work as quickly as possible to get a vaccine candidate developed. It's going to take time. We don't expect to have anything close to a vaccine ready for weeks or months. And that is something that is a high priority, but there's not really a way to speed it up any faster than we're already working on it.

We also have the sobering information that the strain of avian influenza involved in this outbreak is not sensitive to two of the very traditional drugs that we use to treat influenza, but it does appear to be sensitive to oseltamivir, which is the drug that we have been using for the H3 influenza that was circulating in the United States. And so, fortunately, that will--may offer some protection as a prophylactic agent in certain high-risk situations or possibly even benefit individual people who are ill with the disease.

CDC is also developing diagnostic test kits in conjunction with WHO and investigators and making these kits available in Asia so that the clinicians there can accurately diagnose cases of influenza. Of course, one of the things we worry about in many of these parts of the world that don't have the same kind of disease detection capability that we have here is that we will miss cases and that the problem could be more widespread than we appreciate from just the limited information we have available.

Right now, as I said, the human cases are in Vietnam and Thailand, but given the widespread regional distribution of the virus in poultry, it would not be at all surprising to see cases of influenza, avian influenza in people in other countries. And obviously we are hoping to help alert the clinicians there to be on the lookout for this.

We've translated our information about this virus and will be translating our updated infection control recommendations into the relevant languages to serve as a supplemental tool and assist the WHO in their efforts for early detection and proper clinical care of the patients.

The last thing that we're doing here is reviewing our own domestic infection control guidance, so in the worst-case scenario, if we should have a patient with this disease and there's any suggestion of the possibility of person-to-person transmission, which we haven't seen yet, we would have the appropriate infection control guidance already in place. Of course, that guidance is going to be very similar to what we've used for regular influenza or for SARS, and we will be able to provide a more scientific framework around that as we learn more from the investigations that are ongoing in Asia.

So this is, again, a situation that is not currently a problem directly in the United States, but because there's such widespread involvement of the birds in that part of Southeast Asia and these viruses are known to have the potential to evolve, we are stepping out as far in front of this as we can and doing everything possible to assure that we can detect any potential for cases evolving here and initiate the appropriate containment and treatment measures for the affected people.

So let me stop now and take any questions that you might have, and there are questions here in the room.

QUESTION: Given the fact that there's no human-to-human transmission known yet, the only way it could come here is via birds, which would then infect birds here, which could possibly infect humans, which hopefully is not going to happen. But is there anything to protect U.S. citizens from importation of any kind of birds from that region? Has anything been put in place? It's not really a CDC question, but that's one way to stop it from entering.

DR. GERBERDING: Yes, the government has instituted appropriate means to prevent the importation of birds that could be carrying avian influenza from the affected countries. In addition, exotic birds that we might not normally think of as potential carriers are placed in quarantine before they are allowed to be transferred anywhere in the United States. So the steps that are appropriate to preventing importation through commercial means are in place.

The issue of migratory birds has been raised, and it's not yet proven that the virus has moved into migratory bird populations in Asia. Experience in the past has indicated that the migratory patterns of birds that affect Asia do not generally make their way to the United States, but that's something that, of course, remains an open question, and individuals responsible for monitoring the health of birds are very vigilant and will be checking for any indication of involvement.

QUESTION: Maryn McKenna from the Atlanta Journal-Constitution. The newest news today I think is the confirmation of H5 in mainland China, in at least one province, and the virus being suspected in two more.

So for the past couple of weeks, I think as the virus has been found around the Pacific Rim, people have been looking China--at China as the "dark hole" on the map where there were no cases, where there should be since that's the historic home of new flu strains.

So I'm wondering if you can address, given that the virus has now been found in China, is this something that you expected all along?

Is it something that ratchets up your degree of alarm and is there anything that the CDC's collaborative network of flu detection in mainland China can address or help you to do surveillance for?

DR. GERBERDING: I'm aware of a report of virus in China, although I don't believe we have the virus here and I'm not sure we've confirmed those reports yet. But just looking at the geographic distribution of where we have been able to confirm the infection, it's not surprising that eventually we would be able to find it in most of the countries in that area, including China.

As you know, this is a disease that primarily affects domestic chickens and other animals. These are, by definition, usually in rural areas and so the ability to detect flocks that are ill or to know that there's a problem there is somewhat difficult when you don't have access to those more remote areas.

So I think it's often true, in past outbreaks, that there's a delay in recognizing that there's infection in poultry flocks simply because of the rural nature of that industry and the lack of access to surveillance and laboratory capabilities there to really confirm it.

So this is obviously important. If it proves to be true, it will have implications, again, for the clinicians in those areas to be on the lookout for people with respiratory illness that could be avian influenza, so that early intervention and management of affected flocks of birds can be initiated quickly.

Yes?

QUESTION: Trevor Petafor from Fox Five. Are there--what are the similarities between the bird flu and any human flu virus, and what is the likelihood of that mutating and creating that, what we're concerned about, that human-to-human transmission?

DR. GERBERDING: In a short answer, flu viruses come in 15 different strain types and that's designated by the H part of the name, so when we say H3, which was the type that was causing this year's flu outbreak here, and this is H5--the first three types, H1, 2, and 3 are the flu viruses that typically affect people, and the rest of them are usually not human viruses and generally affect birds or other animals.

And so in this case, the H5 strain is antigenically quite different or immunologically quite different from the human strains.

But we know that when viruses from different sources end up in the same animal, or the same bird, the same pig, or possibly the same human, they can exchange their genes, and so they can adapt characteristics that might allow them to become more easily transmitted.

Another aspect of this that's important in predicting what would the health consequences be, should a flu virus such as this become more readily transmissible, is that human beings generally have had no exposure to these viruses, so we would likely have very little intrinsic immunologic protection. That's something, you know, that is very sobering to us, and one of the reasons why, again, CDC is doing everything it can to support the containment efforts that are underway in Asia, and also to be extremely vigilant for any potential exposure here in this country.

May I take a question from the phone, please.

MODERATOR: Thank you. Laurie Garrett with Newsday, your line is now open.

QUESTION: Yes; thank you. Good afternoon. I have two question that are somewhat related. First of all, in terms of the ages of the victims, both those ill and those who've died, they're very, very young.

As far as I know, nobody over 30, and most of them children.

Do we have enough information? Have any of the CDC investigators been able to determine whether this is a function of epidemiology, meaning children are more likely to pick up and play with chickens, or is this immunology perhaps suggesting that this particular H5N3 constellation has in fact circulated the world before and people over 30 may have some residual immunology, or immunological response?

And the second question is on the genomics of this particular strain, we know the Hong Kong strain of avian flu five years ago had a single nucleotide change that allowed it to infect human cells.

Have we been able to get down to the genomic level here to determine whether that same nucleotide shift occurred, or another one, and how distant, at the transmission genome point, is this strain of avian flu from those that commonly infect human beings?

Not the H5N3 constellation per se but the actual genomic capacity to infect the human cell?

DR. GERBERDING: Thank you, Laurie, you're asking the questions that we want to get answers to very quickly but we don't have answers to those questions yet.

The age distribution of the cases that we are aware of in Asia is biased towards younger individuals and whether that has to do with the fact that children become sicker if they're infected, or they're more likely to be hospitalized, or just is a bias of our inability to find all of the cases remains to be seen.

We need to do a lot more work to understand the full spectrum of exposure, whether or not there are exposed people who don't get sick, and what kinds of immunologic protections are relevant.

So we're very early in this and we just simply don't have those answers at this point in time. That's one of the things that our investigators are working hard to ascertain there.

The genomics, likewise, are under intensive evaluation. We have sequencing going on here and in other laboratories. We can't say right now about the sequence information that would predict pathogenicity in human beings. We were able to identify the sequence change that likely accounts for the resistance to the amantadine drugs, but there's still a lot more work to do in comparing these isolates and really getting to the bottom of that. So it's a work in progress and we look forward to having those answers as I'm sure you do too.

Let me take another telephone question, please.

OPERATOR: Thank you. Seth Borenstein with Knight-Ridder, your line is now open.

QUESTION: Thanks, Dr. Gerberding. In terms of the U.S., are you looking at any stockpiling or increased purchase of the one antiviral that does seem to work here, since it's going to be a global market if things get bad? And what about in terms of a avian monitoring system in the U.S.? Is--has there been any work on looking at poultry here to catch early on?

DR. GERBERDING: Thank you. When we were in the midst of the most severe phase of the H3N2 outbreak earlier this season, Secretary Thompson asked us to initiate steps to enhance our supply of oseltamivir should we need it to treat people with influenza in this country. So that proved to be a very prescient recommendation. We have been able to negotiate with the company. We're in the process of accessing a significant stockpile of drug.

Avian monitoring systems do exist in this country. There are a number of different means of conducting surveillance in sentinel chickens and other measures, and it's obviously a high priority for the folks at USDA and in state agricultural departments to make sure that there are sensitive means for detecting illnesses in domestic birds as well as any reported illnesses in migratory birds.

Let me take another telephone question, please.

OPERATOR: Thank you. John Softchek with the Washington Fax, your line is now open.

QUESTION: Thank you. Dr. Gerberding, I understand that the process that WHO and CDC are using to create the seed viruses, is that commonly referred to as reverse genetics?

DR. GERBERDING: That's one terminology, yes.

QUESTION: Okay.

DR. GERBERDING: Excuse me. We've lost your connection, so we'll try to get back to you as quickly as we can restore it.

Have we lost the entire telephone connectivity?

OPERATOR: Mr. Softchek, your line is now open.

QUESTION: Yes. Dr. Gerberding.

DR. GERBERDING: Thank you. We've got you back.

QUESTION: Thank you. My question was I understand that the FDA has yet to approve any vaccines created through reverse genetics, and I'm just wondering how much of a barrier, obstacle, problem would that be once that vaccine was created to getting it approved in the U.S. if it needed to be?

DR. GERBERDING: Well, like any new health challenge we want to make sure we're balancing the need for a speedy effective health intervention with the safety of that intervention. And one of the best ways to do that is to work with the FDA and the manufacturers from the very beginning of the process, and that's the strategy that we'll be working on in this particular situation. So that we'll identify the regulatory issues as we go forward, and work this through in parallel rather than in series.

So anything that can be done to safely speed up the development of a product is going to be done. Secretary Thompson has been very adamant about that.

Is there another question from here in the room?

QUESTION: Both Thailand and Indonesia have revealed in the past week that they knew that they had avian influenza in their countries for a number of months. In the case of Thailand, possibly back to October, in the case of Indonesia, possibly back to November. Two-part question. First, do you have any concerns about the length of the time that the virus will have been circulating there? And second, looking back to the SARS epidemic, clearly one of the reasons why SARS spread as it did was because of delay in news coming out of China. Is there anything that the CDC can do on its own or through its partners in the WHO or in its people on the ground in Asia, to the underlying two foreign governments that this didn't work the last time around?

DR. GERBERDING: Thank you. I think everyone understands how important it is to identify these emerging health threats as quickly as possible, and the challenges are many. I already mentioned the issue of the rural distribution of the emergence location when you have something coming up in a flock in a rural community that doesn't have necessarily veterinary service and doesn't necessarily have laboratory service, and clinicians who might not recognize that the human disease is anything unusual because it really is an influenza-like illness and there are so many causes of that.

It's just very challenging to see that something is happening in real time.

CDC has a very important international emerging infections program in Bangkok where we are involved in the very active surveillance of certain respiratory illnesses in some of the areas of that country, and have a very robust interaction with the Minister of Health there. We have had a training program there in epidemiology for 26 years, and so there's a large cadre of very trained and skilled epidemiologists and migratorians in that country who I think are evolving very effective surveillance systems, but it is very important to recognize that the surveillance systems in humans have to be linked with the surveillance systems in animals. Even here in the United States, that's something that only recently have we begun to prioritize.

Eleven out of the last 12 emerging infectious diseases that we're aware of in the world that have had human health consequences have probably arisen from--arise from animal sources. So what we really need to work on is not only recognition of illnesses in flocks of farm animals, but also the relationship between the human health surveillance system and the animal health surveillance system.

And one very important point of intersection is, of course, the laboratories. The technology necessary to identify all of the possible things that could emerge as a pathogen in these environments is very high level, and we have to, I think, do more to share our laboratory capacity and our laboratory development with these countries. That's one of the goals of our emerging infections program in Thailand, likewise in Vietnam. They have very similar challenges in these countries.

So early recognition is what everybody wants, and we're very pleased that in our '04 appropriation from Congress this year we received some additional resources to help develop a global detection system, and one of the places we'll be looking at utilizing those resources is in Southeast Asia to see whether or not we can be able to support the laboratory and epidemiologic capacity there and reduce the time.

You asked me also whether I was concerned about the time of circulation. I don't think we have accurate information yet about when the first cases actually emerged from a scientific perspective. But, of course, the longer a virus is circulating, the more likely it is to evolve. The fact that if it has been there for this period of time and we have not seen large numbers of human disease suggests that it is not evolved to the point where it's efficiently being transmitted to human beings, and certainly we have no evidence that it's being transmitted from person to person. So that's a good sign if it really has been circulating in the animals for that period of time.

Let me take a phone question.

OPERATOR: Thank you. David Brown with the Washington Post, your line is now open

QUESTION: Thanks. Dr. Gerberding, given the fact that if there is a reassortment and this virus starts transmitting efficiently between human beings, a vaccine will be useful right then, and the fact that it takes four to six months to develop a vaccine, once a seed virus, prototype seed virus is ready and, you know, produced, are you going to suggest that the United States government contract with a drug company to produce some H5N1 vaccine that can be on the shelf ready for use in case this does become a human disease?

DR. GERBERDING: I think the way we're approaching this is in a very phased approach. The most important thing right now is to get a vaccine candidate. Whether or not that candidate gets developed depends on what the outcome is of the situation in Asia. As containment is successful, it obviously becomes less urgent. As we know more about the genomics of the virus or whether or not the virus is evolving, that will certainly be a relevant factor. And ultimately the epidemiology will dictate whether or not a vaccine is necessary to protect humans.

So a lot more information needs to be available before I can really speculate and offer an answer to your question.

If the worst case occurs and we have a virus that can be transmitted efficiently, then certainly developing a vaccine as quickly as possible is going to be a high priority. And I think that's why we're so aggressively pursuing those seed cultures already.

Let me take a question here in the room.

QUESTION: Most folks in the U.S. are not familiar with the avian flu because we haven't had any time that I can remember. Can you explain what the difference is, should they be more afraid, less afraid in terms of symptoms if it were to come here? And then one of the things that was mentioned earlier by the WHO was that they were a little concerned, it sounded, that the confirmed case--at least confirmed by them, it appears--in China was in ducks, that it killed a duck, and the fact that ducks are usually birds that carry the virus but don't die from it seems to indicate it may have changed already.

That might throw another winkle in this. How concerned--it kind a goes along with the other question. With the reporting, it's a global problem. Do these countries have the resources similar to what the CDC's investing in order to inform the public, to do the research, et cetera, to prevent this from getting bigger in that region?

DR. GERBERDING: Yes. When we talk about avian influenza, it's actually not accurate to refer to it as "it." There are a family of avian influenza viruses and like the human influenza viruses, each time one emerges to cause a problem, it's a little bit different usually than the previous one.

So the avian influenza virus is right now causing a problem in Asia, does seem to be associated with serious respiratory illness, at least in the documented cases that we've seen--pneumonia that follows after fever, muscle aches, and the usually serious flu illnesses that we see here.

So clinically, we're not aware of any distinguishing characteristics from that flu syndrome compared to a severe case of flu here but we have a lot to learn about the spectrum of illness, and until we do antibody studies and other more perfective evaluations of exposed people, we just won't know what the full extent of illness is.

Avian viruses at other times have had milder disease. There is an avian influenza problem in the Netherlands that primarily involved infection of the eye, although there was one individual there who died as well.

So the spectrum of illness fortunately is not something we know very much about because usually there are not very many human cases, and so our information is just based on a very small number of affected people, and hopefully it will stay that way this time as well.

You also asked about countries with the involved, who are involved in this problem, whether they have the resources to do all of the state-of-the-art things that we would like to be able to do and the answer is no, of course not.

That's why the World Health Organization is there, that's why the international community does contribute, and we have the WHO collaborating laboratories of which CDC is one, who are certainly applying their scientific expertise and their very best virologists to work on this problem.

So this is an international effort because it's a global problem and as we have learned over and over and over again in the last two years, our emerging infection diseases really are global problems, whether they're in our backyard or not.

We have to all take responsibility and shared ownership in dealing with them.

Let me take a telephone question, please.

MODERATOR: Thank you. Anita Manning with USA Today, your line is now open.

QUESTION: Hi; thanks. Dr. Gerberding, well, let's see, I have so many questions, but one of them is is there any indication of involvement of pigs in Asia and you mentioned that if containment of this is possible, you know, that's the goal and that's the hope, and then a vaccine would be less urgent.

But with it popping up like this all over the place, is containment possible?

DR. GERBERDING: The pigs have not yet been identified as being sick but we are working with the other investigators to evaluate pigs on farms, particularly farms that also have affected birds, and pigs are being sampled, they're being tested with PCR tests to look for DNA from the influenza viruses, and I'm sure that other blood tests will be done as well as tests of their secretions in their feces. One should be able to identify any potential influenza viruses of any type that they might be harboring.

But so far I'm not aware of any reports of illness among swine or other large mammals.

The containment effort obviously has to be very aggressive and the faster the better.

In Hong Kong, where there was a prior problem with influenza, a very massive culling of the animals, the bird population did result in successful containment of the problem.

Those efforts are underway in the affected countries. I don't have information today to define the coverage of the efforts, and what proportion of affected animals, or bird flocks have been culled so far, but that's obviously a very high priority.

It is challenging because of the widespread geographic distribution and the many locations where birds are kept and I think it will be a challenge to be able to successfully eliminate the virus through culling.

But we also don't know what happens, what's the nature history in a flock of birds. For example, it's possible that birds become infected, they get sick, they die and infection could self-extinguish if there are no uninfected birds around.

We don't know whether birds can develop protective immunity or not.

There are many questions here that will shape the scope of this problem and I think right now the priority is just simply to identify the affected flocks and take the appropriate, aggressive, rapid steps to eliminate affected birds from the environment.

Let me take another telephone question, please.

MODERATOR: Thank you. Daniel DeNoon with WebMD, your line is now open.

QUESTION: Thank you, Dr. Gerberding.

The information on pigs--if pigs were identified to have either a human or avian influenza virus in these areas, what steps would be taken in those cases, given that pigs are sort of seen as a mixing pot for these kinds of reassortments?

DR. GERBERDING: Well, you know, lots of animals can serve as mixing pots, as you say, for reassortment of influenza viruses, and until we know more about what strains are involved and what the pattern of the virus really is, I can't really speculate on whether it would be indicated to take any measures to contain the pigs.

At this point we just don't have an answer, we need to get the data and really look at it in the context of what we know about the evolution of influenza viruses in swine, bird, and in humans. So stay tuned for more information on that.

A question here.

QUESTION: To refer back to some things you already said, you said that the setting in Asia in which these poultry and human cases are now happening are mostly rural settings in which there's not a lot of diagnostic capacity or a lot of lab capacity.

Given that that's the case, if there were a reassortment event and the virus acquired the ability to move easily from person to person and started to do that, what is the likelihood that you would find out about that in a reasonable period of time?

DR. GERBERDING: Well, under normal circumstances, the surveillance is not focused in all of these remote areas, but right now the light is shining on Southeast Asia and we have a large number of international investigators who are there working with the local public health and veterinarian, and agricultural communities to make sure that the word is going out.

For example, we have CDC staff in Thailand who are working very hard to disseminate alerts and information through their chain of in-country clinicians and experts who are involved in public health efforts.

This is a time where you draw upon all of the collateral capabilities that you have.

There are reasonable public health infrastructures in some of these countries and quite good public health infrastructure in some of the countries. So there are ways of making this work and when people are pessimistic about containment, I just think it's important to remember that China did in fact contain SARS and that was also a very, very challenging public health situation, and yet by engaging their full complement of public health officials, with clinicians, government workers, and a whole cadre of others, they were able to isolate and contain that virus.

So I don't think we should be pessimistic. I think we should be realistic about the challenges that are ahead and we at CDC are certainly committed to doing everything we can to support our neighbors and colleagues in Southeast Asia and to share in the WHO effort to get this problem under control.

So with that let me thank you for your attention today and we will of course be learning a lot more about this as we go forward, so we're committed to providing regular updates as we have new information to report.

Thank you.

Listen to the telebriefing

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