Transcript for MMWR Telebriefing: Evidence of Recent H5 Bird Flu Infections among Dairy Workers and CDC Guidance Updates

Please Note: This transcript is not edited and may contain errors.

Operator - 00:00

Welcome and thank you for standing by. At this time, all participants are in a listen only mode until the question and answer session of today's conference. At that time, you may press star one on your phone to ask a question. I would like to inform all parties that today's conference is being recorded. If you have any objections, you may disconnect at this time, I would now like to turn the conference over to Benjamin Haynes, thank you, maybe again.

Moderator - 00:23

Thank you Courtney, and thank you all for joining us today as we release a new MMWR and updated CDC guidance on the H5N1 bird flu outbreaks. We're joined today by Dr. Demetre C. Daskalakis, Director of the National Center for Immunization and Respiratory Diseases and CDC Principal Deputy Director, Dr. Nirav Shah, I'd like to remind everybody that this briefing is embargoed until 1pm Eastern, when our MMWR goes live on the CDC website. I'll now turn the call over to Dr Daskalakis.

Dr. Demetre C. Daskalakis - 00:58

Thank you and good morning everyone. I will first provide an update on H5 cases in the United States. Then we'll share some findings that are being published in an MMWR later today. So first, the situation overview. To date, there have been 46 human cases of H5 in the US, in 2024 25 cases were due to the ongoing outbreak in dairy cows. 20, which of which are 21, of which are in California. 20 cases are due to poultry depopulation, including the 11 recent cases from Washington State. Additionally, there is one case in Missouri with no known animal or animal product exposure. CDC continues to assess the risk to the general population is low. Efforts to protect people with exposure to animals or animal products affected by H5 continues to be a key focus of our public health activities. I'd like to now share the results of an important study focused on workers that will be published in the Morbidity and Mortality Weekly Report later today, or MMWR. So this is the Michigan Colorado dairy worker survey, CDC, coordinated with state health departments in Michigan and Colorado to conduct an anonymized serosurvey among dairy workers exposed to dairy cows infected with H5N1 influenza A. So as a reminder, a serosurvey is a collection and testing of blood from a defined population. In this case, dairy farm workers to estimate the prevalence of antibodies against an infectious pathogen, in this case, H5N1, as an indicator of possible exposure prevalence or immunity. The purpose of the serosurvey was to expand our understanding of the extent of infections among exposed dairy farm worker workers, how these infections related to symptoms experienced by participants, and what activities or actions were associated with infection. Blood samples were collected from June to August 2024 from 115 people who worked on dairy farms in Michigan and Colorado with cows that were confirmed positive for H5 virus. 35 of the people included in this serosurvey had results previously reported earlier this summer, and as a reminder, there were dairy farm workers from Michigan and all tested negative for H5N1 antibodies. 80 additional people were recruited in Michigan and Colorado to increase the sample size of the serosurvey and provide more robust results. Samples were collected 15 to 90 days after H5N1 virus was identified in cows on the farm. Along with getting their blood drawn, individuals were interviewed to learn more about what they did on the farm, what protective measures they took, and whether they had been sick since cows on their farms had been diagnosed with H5N1 or quarantine. All samples were tested for antibodies against the H5N1 virus isolated from the first human case this year in Texas. And we also tested samples against a seasonal H5N1, virus as a positive control. So on to the results, eight of the 115 samples, that's 7% were seropositive against HPAI, or highly pathogenic avian influenza. The 2.3.4.4b A clade that we see circulating among dairy cows using two different antibody tests to be considered antibody or seropositive, both tests had to be positive using accepted criteria. Another lab protocol was also performed to remove seasonal influenza antibodies and to rule out that the positive H5N1 tests were due to cross reactivity related to these commonly circulated viruses. On to the specific results, 8 of the 115 people tested positive for H5N1 antibodies using this protocol of the seropositive individuals, four remembered having symptoms, mostly conjunctivitis. The other four did not among these four people, illnesses began prior to or shortly after identification of infected herds, more details of who was who had positive results. All eight were Spanish speakers. All eight reported milking cows or cleaning the milking parlor, supporting these as higher risk activities, none wore respiratory protection, and less than half were eye protection, highlighting the need for better tools to support worker protection. Only one person reported they worked with infected cows, despite the fact that they were working with cows on farms with known infection. One important limitation to the survey data is that the interviews were conducted on an average 49 days after the first exposure to infected cows with some workers interviewed up to 90 days after their first exposure. That makes recall of minor symptoms potentially difficult. Nevertheless, these data help us better understand the potential for infection with mild or no symptoms, as well as highlighting interventions that may help workers reduce their risk of exposure and infection with H5N1.

I'll now hand the mic over to Dr. Shah, who will go into more details about actions that CDC is taking to further mitigate risk to people who work with animals and animal products potentially affected by H5N1 Dr Shah.

Dr. Nirav Shah - 06:05

Thank you, Dr Daskalakis, and good morning everyone. This is Nirav Shah from CDC, and I'm going to be discussing the steps that CDC is taking in light of the serology results that Dr Daskalakis just outlined. The purpose of these actions is to keep workers safe, to limit the transmission of H5N1 to humans and reduce the possibility of the virus changing right now. There are two principal ways that people in the United States are being infected with H5N1 via exposure to infected poultry during culling events, and via exposure to infected dairy cows during the milking process. What we are announcing today is an intensification of recommendations to focus on the highest exposure tasks in poultry and dairy operations, ultimately to reduce the risk of infection. We're doing so in three areas. Number one, expanding our recommendation for who should be tested for H5N1. Number two, a new recommendation for use of Tamiflu for exposed, asymptomatic workers. And then number three, focusing our PPE guidance for workers based on their risk of exposure coupled with additional training activities. So let's start with testing the serology data that Dr Daskalakis outlined show that there may be individuals who were infected with H5 but who do not recall having symptoms. That means that we in public health need to cast a wider net in terms of who is offered a test so that we can identify, treat and isolate those individuals. Now, previously, as part of an outbreak investigation, we focused on workers who were exposed and who had symptoms. Going forward, CDC is expanding our testing recommendation to include workers who were exposed and who do not have symptoms, particularly those workers who were exposed without having worn proper PPE. Again, we're expanding our recommendation to include workers who were exposed and who do not have symptoms, particularly those who were not wearing appropriate PPE. The purpose of this expansion, informed by the new serology data, is to actively identify exposed workers with H5, even if their symptoms are so mild as to be unnoticeable, so that those two that those workers too, can be offered treatment and isolation. This active case finding reduces the likelihood that a mild infection could turn into a severe infection, or that the infection spreads to anyone else. Simply put, the less room we give this virus to run, the fewer chances it has to cause harm or to change. And the best way to limit the virus's room to run is to test, identify, treat and isolate as many cases as possible in humans and as quickly as possible. Second, let's turn to our new recommendation for medication for exposed asymptomatic workers. A key part of our strategy is to offer treatment with Tamiflu to workers who were exposed and who show symptoms that are consistent with H5N1 infection, but in light of the data that Dr Daskalakis outlined, which showed again, the existence of individuals with mild or even no symptoms that they can remember, CDC now recommends offering Tamiflu to asymptomatic workers who had a high risk exposure to H5N1 animals without having worn adequate PPE. Again, we are expanding the scope of who CDC recommends Tamiflu for to include now workers who are asymptomatic, who had a high risk exposure to an H5N1 infected animal without having worn adequate PPE. So what's at high risk exposure? Well, that could include an unprotected splash in the face with raw cow milk or on the poultry setting, something that might have happened during a depopulation or culling event where the individual was not wearing appropriate PPE. Just as with our expanded testing recommendation, more widespread use of Tamiflu achieves several goals. Chief among them is to protect workers. It reduces the likelihood of an asymptomatic case being symptomatic because they're receiving Tamiflu, and thus, it lowers the risk and the chances of onward transmission to close contacts, and then the third thing is our focus on PPE guidance to farms and workers based on their risk level. CDC continues to focus on primary prevention strategies like PPE for workers with potential occupational exposures to animals or to animal products that are infected by H5 in light of the serology data. CDC is updating our PPE recommendations for workers based on their risk of workplace exposure going forward. CDC PPE recommendations will prioritize what PPE a farm worker should wear based on our data indicating which farm tasks present the highest risk for H5N1, exposure and infection, for example, culling operations or working in the milking parlor with sick or infected animals, simply put, the higher risk activities will call for more PPE use. CDC has developed additional resources to support training workers on PPE use and to explain its role in preventing H5N1 from animals infecting humans. CDC will continue to evaluate this situation and will update our guidance as needed. To close, what we've discussed today is an example of CDC using data to drive action. We will continue working with trusted partners to reach farm workers and their employers to communicate these prevention strategies as widely as possible. And then finally, before we open it up to questions, we will, we anticipate publishing a spotlight today that contains these updated recommendations. With that, we'll turn it over back to our team for questions.

Moderator 12:34

Thank you. Dr. Shah. We are now ready to open up for questions.

Operator - 12:39

Thank you. We will now begin the question and answer session. If you would like to ask a question, please press star one. If you need to withdraw your question, press star two. Again to ask a question, please press star one. Our first question comes from Brenda Goodman from CNN.

Brenda Goodman - CNN - 12:58

Thank you so much for taking my question and congratulations on these studies, because I know you had some significant headwinds to get them done. I have a question about the eight workers, are they counted as cases now? Or will they be counted as cases in the human case count? And then I was curious. You gave an update at the beginning. Dr Daskalakis about how many human cases of H5 were associated with poultry depopulations this year. Why do you think we're so many seeing so many more human infections with poultry depopulation because we've had age five in poultry before, and I think we only had one case prior this year.

Dr. Demetre C. Daskalakis - 13:38

Great. Thank you for those questions. So on the first question, these retrospective serologies are not going to be reported as cases, so they are really looking retrospectively, helping us learn, but they're not going to be called cases. On the second question, I think there are a lot of reasons why we could potentially be seeing more human disease related to or human infections related to the culling operations. One is there's more H5, so that's probably one of the most important. Like both in wild birds as well as in poultry, we're seeing a significant increase, and the more the sort of H5 community viral load is high in animals, the more likely it is that humans will be exposed. I think the second is also that we, I think, have raised a lot of attention to carefully screening individuals with H5 exposure for even mild symptoms. So there could be that as well. In terms of other characteristics of the virus, we are not seeing any changes with the virus that would indicate ease of transmission. But given sort of our current environment, the sort of increasing experience with age five and one really creating strategies to better protect workers based on this data is, I think, the right thing to do at this time.

Operator - 15:00

Our next question comes from Megan Molteni from STAT

Megan Molteni from STAT - 15:06

Thanks for taking my question. I was wondering if you could clarify something that you said about only one of the persons who tested positive for antibodies reporting having worked with known infected cows, and it sounded like you were saying that that meant there was a need for more additional education. But could it also be that these animals that they're working with are asymptomatic, and so, you know, they're going through the milking parlors and they're not getting separated out into quarantine? Can you talk a bit about what we know about asymptomatic disease in the animal.

Dr. Demetre C. Daskalakis - 15:41

Great. Thank you. So. So I think that you put the nail on the head that this is really about about education and also self-assessment of risk, which I think is an important piece of both why one would wear post, why one would wear appropriate PPE as well as pursue post exposure prophylaxis. So these were farms with known infected cows, and so it was really about the fact that they didn't have the awareness that they had any sick cows that they were working with, even though they were in environments where sick cows were known. So it really speaks to the importance of more on farm training around H5 as well as ways to protect from H5

Megan Molteni from STAT - 16:22

Okay, thank you. Can you also just, very quickly, are there any more serology studies planned in other states, like thinking about California, given the number of herds we see there now.

Dr. Demetre C. Daskalakis - 16:33

Thank you for that question. So we are currently working, and I think we've, we've put this up on one of our prior spotlights on a serology study, a serosurvey, that is that was conducted it physically in Ohio, because there was a large convention of bovine practitioners, and so we about 150 of them provided blood samples as well as survey data. And we will update on those once they become available.

Operator - 17:04

Our next question comes from Josh Nathan-Kazis from Barrons.

Josh Nathan-Kazis from Barrons - 17:08

Sorry. Thank you so much. Two quick questions. One, I wonder if you could have some context. I mean, how unexpected is it that there would be asymptomatic HVAC cases? That's something that's been seen before elsewhere. How much of a surprise of the finding and separately I saw in the MMWR says that 40% of the workers reported feeling ill while H5 was on their farm, although only a fraction of those actually had serological evidence of infection. I wonder, if you just talk about what might be going on there and why so many of the workers said they felt sick, even if their blood tests didn't say they were sick.

Dr. Demetre C. Daskalakis - 17:46

Thank you. So on the first question, I think that the only way to sort of take out surprises by doing the studies, which is why it's important that we have that information. But I think given the mildness of the symptoms that many people are presenting with, it's not a surprise that some people wouldn't recall symptoms up to 90 days after their exposure. So again, though not surprising, it actually is approximately in line with other serosurveys that have been conducted that focused on, on, again, this specific clade of H5N1, so a study that happened in workers, 2223 showed about 4.6% were seropositive, and about 14% as you recall from a pre print that UT Galveston Galveston put out in early 2024 also showed asymptomatic individuals with infection. So again, not surprising, but in line with some of the other data. Now, question two, not every respiratory symptom is related to H5N1. And so we've actually seen in other environments that there is several other viruses that could explain respiratory symptoms. So in this circumstance, though there was not serology done for other respiratory symptoms, that likelihood is that the illnesses that they that they experienced, were not caused by H5N1 based on our testing criteria. Over,

Dr. Nirav Shah - 19:13

Hey Josh, this is Nirav. One other point you noted, or you framed some of these results as asymptomatic, the structure of the survey itself doesn't demonstrate whether these individuals were asymptomatic or whether they just couldn't remember having had symptoms. And so the most we can say is that they can't remember having had symptoms. Some of them may have had mild symptoms that, again, were unmemorable. Some of them may have been indeed asymptomatic. The data that we have does not allow us to determine which of those it was, and so for that reason, we're not characterizing these as asymptomatic. All we can say is that they don't recall having had symptoms.

Operator - 19:55

Our next question comes from Erica Edwards.

Erica Edwards - 20:00

Hey, thanks so much. I appreciate the opportunity. And a couple questions. One is about the severity of H5N1 illness in people. I mean, obviously previous estimates from other areas of the world have quoted mortality rate of at least 50% I'm curious what you're learning about from studying the H5N1 infections here in the US that I think would be quite mild. What's different here? And then, if I also could ask, could you talk about any work that's being done to develop rapid tests, H5N1? Thank you.

Dr. Demetre C. Daskalakis - 20:32

Thanks for that question. So on, the severity, again, what we've been seeing in the United States is extremely mild symptoms. So again, ranging from moderate to mild conjunctivitis, and some people also experiencing mild respiratory symptoms, and also some with constitutional symptoms, like there have been some folks with beavers. So, you know, I think that there are a couple of hypotheses, which is all that we can really provide as to why there's a difference in severity. One, you know though, though H, all, H, 5n, ones are not built the same. So these are actually potentially different genotypes. So we know that there's sort of different clades and genotypes circulating. So what we have in the US at this point has only caused mild illness. Also, there could be issues related to the populations that are exposed to the virus, as well as to the magnitude of the exposure. So again, all hypotheses. So we don't have a very clear answer, but from the perspective of what we're seeing in the US, everything has been mild.

Dr. Nirav Shah - 21:40

And then this is Nirav on your latter question around rapid tests. So CDC has been working very closely with our colleagues at NIH particularly their rad X program, to evaluate some of the rapid diagnostic tests that are already available on the market, to determine whether those tests are capable of detecting H5 These are tests that can already detect influenza A, influenza B, sometimes even COVID in general. But the question is, can they detect H5 the current circulating version of H5 as part of their overall diagnostic approach? And CDC has been collaborating with our NIH colleagues to try to understand the utility of those tests. We don't have a timeline on when those data will be available, but I know that work is underway right now. Separately, we've been working with diagnostics companies to determine what types of additional rapid tests might be useful in the marketplace to try to move or shorten the duration between becoming symptomatic or exposed and then being able to have access to testing. Clearly rapid test still an important niche there, so we're very much in favor of them. We've just got to make sure that they are capable of serving that purpose.

Dr. Demetre C. Daskalakis - 22:48

Just one other thing to add is CDC will also be working with with a couple of states, to do a testing pilot where we're actually assessing a near point of care, or point of care test against lab based testing for H5, so that will also help elucidate some point of care strategies or or self-testing that may help in the future.

Operator - 23:15

Our next question comes from Washington Post.

Washington Post - 23:21

Hi. Thanks for taking this call. Two questions. One, you mentioned one of the justifications for these precautionary measures being preventing onward spread, but we've also been hearing there's no evidence of human to human transmission. So does this new data create any concerns that some of these dairy workers may have been spreading the virus among each other, and then the second one is now that we have an incoming administration that's promised mass deportations. Are you worried about about a cooperation with these, investing with these investigate public health investigations in the future? Would you get the same kind of cooperation that you did with with workers, if there's a potential, if there's mass deportations looming, great

Dr. Nirav Shah - 24:07

This is Nirav as to the former question, I'm glad you raised that for avoidance of doubt and for clarity, there is nothing that we've seen in the new serology data that gives rise to a concern about person to person transmission. So to your point that you made about, why are we going this extra step with additional testing and Tamiflu to further in that regard? And the answer is to drive that risk down as low as possible. This is fundamentally a respiratory virus, and although we have not seen changes to the virus that would suggest the capacity for it to spread from person to person. We want to keep that risk as low as where it is right now, one of the best ways to do that is to identify individuals who have been exposed through greater testing and provide them with Tamiflu to drive down the levels of virus in their body, which, again. Helps us keep that low risk as low as possible. As to your latter question, we're not commenting on anything related to transition or an incoming administration. We're focused today on the serology data and the CDC actions therein. Thanks,

Moderator - 25:15

Cortney. We have time for two more questions, please.

Operator - 25:19

Our next question comes from Youri Benadjalud from ABC News.

Youri Benadjalud from ABC News - 25:22

Thanks for taking my question. This data seems to support that there are a lot of cases that are potentially being undercounted, and there's only 46 confirmed by the CDC so far. How many cases in across forums, in the US, do you think that could actually be out there? And then I'll have a follow up, please.

Dr. Nirav Shah - 25:43

Thanks Yuri. Our data suggests that there in any outbreak situation, we know that there are individuals who may have been exposed, may have been infected, who are not part of the count. This is what serology data helps us get a better retrospective understanding of we still need more data to better characterize that so we can't speculate today on how many unidentified cases that there might be. We've always known that that's a possibility. What these data really help us understand is that some of those workers may have had such mild symptoms, such that they may not recall having been ill, and thus we need to identify those individuals and make sure they've got medication, as I said, in connection with the prior question, to drive their risk of getting ill as far as possible down, as well as to reduce the likelihood of spread. But better characterizing right now, how much of the iceberg is above the water versus below the water. It's not something we have enough data on quite yet.

Operator - 26:43

Our last question was from Kai Kuperschmid from Himes Magazine.

Kai Kuperschmid from Himes Magazine - 26:51

Thanks for taking my question. So I wanted to ask a little bit about the timeline. Here you said the the samples were taken, I think June to August. It's November now, and just in general, I mean, it's taken a long time to get this kind of data. I know a lot of people have been waiting for it. Can you describe a little bit why it took this long, and what the hurdles are to do this, also to do it in other places, possibly. Thanks guys.

Dr. Demetre C. Daskalakis - 27:14

So I think a lot of the timeline is really around just sort of the standard procedures for serology for H5. So the first is again, we had to sort of gather the specimens. They had to come to CDC. And then the subsequent pieces are that these 115 specimens had to be run in our BSL, three labs that, as increasing data emerged, the cross reactivity with seasonal flu became something that we needed to be addressing in the testing. We then had to develop additional protocols to do the adsorption for seasonal flu, then run the absorption and then rerun the tests again. So this was released, really at a good time and a good timeline, given the complexity of non-routine laboratory testing that was needed to be able to characterize these individuals. Thanks for your question.

Moderator - 28:10

I'd like to thank you all for joining us today. If we did not get to your question, or if you have follow up questions, please feel free to call the main CDC press office at 404-639-3286 or you can email [email protected] Thank you for joining us, and this will conclude our call.

That concludes today's conference. Thank you for participating. You may disconnect at this time.

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