TOM FRIEDEN: Good afternoon, everyone. Thank you very much for joining us on short notice. I believe you will all soon be receiving if you haven't already received a report from The New England Journal of Medicine that gives some analysis of the Zika situation. This is a special report. Recently the journal has been kind enough to consider it on a highly expedited basis. I believe they disseminated it within the last few days. We had it peer reviewed and it's an example of a real time analysis and publication of data. This is a study that marks a turning point in the Zika outbreak. It is now clear the CDC has concluded that Zika does cause Microcephaly. This confirmation is based on a thorough review of the best scientific evidence conducted by CDC and other experts in maternal and fetal health and mosquito-borne diseases. We continue to do everything possible to protect pregnant women and we're undertaking further studies to determine the broader range of birth defects beyond Microcephaly that could occur from Zika infection in pregnancy. We believe that Microcephaly is likely to be a part of a range of birth defects that may affect women at a particular time or at any time in pregnancy. There is still a lot that we don't know, but there is no longer any doubt that Zika causes Microcephaly. we're undertaking further studies to look at the spectrum of disorders that the virus may cause, and as with much of scientific research, there is no single piece of evidence that provides conclusive proof of this connection, rather, mounting evidence from many studies and careful review of causal criteria was needed to determine that Zika causes Microcephaly and other birth defects. As you probably know, the Centers for Disease Control includes different centers, one of which is the National Center for Birth Defects and Developmental Disabilities. So we are fortunate to have on staff wide expertise including birth defects and they’re applied two different sets of criteria. There are standard criteria for determining whether a pathogen or environmental exposure causes a birth defect. They were proposed more than 20 years ago, they have been used many times since, they are referred to as shepherd criteria and the article analyzes those along with the data that we have on Zika. we also used a modified kill criteria and the tables in The New England Journal summarizes that information and is a systemization of what we know to date about Zika that allows us to make this definitive conclusion.
I will say that we did not waste time, January 15 within hours of seeing the Zika virus within neural tissue, we began travel advice and then as we learned more, the advice to reduce sexual transmission risk and we've been working intensively with countries confronting Zika and Puerto Rico which has had hundreds of cases. It is worth mentioning that this is an unprecedented association. Never before in history have there been a situation where a bite from a mosquito could result in a devastating malformation and it’s because it was so unprecedented that we have until now waited to say that we have concluded that there is a causal link. But today's article and media briefing is that conclusion. Concluding that an exposure causes a health outcome is like putting together the pieces of a puzzle. Each new study is another piece of the puzzle. Some epidemiologic, some clinical, some molecular, but each new finding, each new data point, all of that information feeds into what we know about Zika and helps us solve the puzzle. But it's worth emphasizing that we still need many more answers, some of which could take years. For example the full range of birth defects associated with Zika, for example also the time in pregnancy of greatest risk and the type of birth defect associated with different timing in pregnancy, there is an international effort to work on this issue. We coordinate closely with other countries, with the World Health Organization and others. Ever since the Zika outbreak began, we have focused on protecting pregnant women by encouraging them not to travel to areas where Zika is spreading. That guidance does not change. If a woman is pregnant, we recommend you not travel to a region with ongoing Zika virus transmission. If you must travel or you live in an affected area, talk with your doctor and strictly follow steps to prevent mosquito bites. It’s important to continue to use condoms if your partner travels in or lives in an area where Zika is spreading or has been infected with the Zika virus. Reducing exposure to mosquitos for everyone in areas where the virus is circulating is important.
There are no changes in the CDC guidelines as a result of this analysis, but it does reiterate the urgency of our response. There are still many unknowns, but the study marks an important development in the Zika outbreak. Never before have we seen an illness threat by mosquitos linked to a birth defect. The science now shows what the hundreds of impacted families have suspected all along. Zika virus is causing the tragic increase in Microcephaly cases and other serious brain defects. I will now turn to the lead author of the study, Dr. Sonja Rasmussen, to discuss this important research, and unfortunately, I will be unable to remain on the call for the question and answer period. But you have a wonderful team of experts at CDC who can answer your questions better than I can. Thank you all very much for joining us.
SONJA RASMUSSEN: Thank you, Dr. Frieden. To assess whether Zika is a cause of birth defects, our team reviewed existing evidence using two sets of criteria. First, we used shepherds criteria, a framework for looking at whether an exposure during pregnancy causes harm to a developing fetus. Shepherds criteria considers two types of approaches to determining whether an exposure during pregnancy causes birth defects, identifying a combination of a rare exposure and a rare defect, and second, strong association consistently observed from well-designed epidemiologic study to confirm a causal relationship. Based on our application of shepherd’s criteria, we concluded the necessary criteria has been met to support the findings that Zika virus is a cause of Microcephaly and other severe brain defects. To thoroughly evaluate all of the evidence today, we also reviewed existing evidence using Bradford hill criteria used to help determine whether an observed link is in fact causal. Our evaluation of the evidence using both these sets of criteria yielded the same conclusion. Zika is a cause of Microcephaly and other severe brain abnormalities. The essential shepherd’s criteria that allow us to confirm the causal link between Zika and Microcephaly are these.
One, exposure occurs at a critical time during pregnancy. From what we know about causes of other birth defects, this critical time is usually early in pregnancy. We determined that this first criterion was met because studies linking Zika with Microcephaly and other severe birth defects of the brain show women who deliver babies of Microcephaly were infected with Zika virus either during the first trimester or early second trimester of pregnancy. Two, a specific defect or a consistent pattern of defect is present. We believe this criterion has been met because Microcephaly and other severe brain defects have been observed in fetuses and infants of women affected with Zika virus during pregnancy. Three, the link involves a rare exposure and rare birth defect. We believe that criterion has been met because Microcephaly is a rare birth defect especially the severe type of Microcephaly that has been observed in the current outbreak. And exposure to Zika is rare in travelers. Yet Microcephaly and other severe brain defects are being observed among women who travel to an area with active Zika transmission even if they were there only for a short period.
In addition, we believe the evidence has been met for another one of shepherd's criteria, the link makes sense biologically. Studies have found evidence of the disease in the brains of babies with severe Microcephaly who died which strongly support this finding. Finally, we also used Bradford hill criteria, another framework to review whether an exposure is a cause of the certain outcome to study the relationship between prenatal Zika virus infection and Microcephaly. We concluded evidence has been accumulated to meet the Bradford hill criteria as well. Now that we've determined the causal the relationship, we can use this information to redouble our efforts to prevent Zika, more narrowly focus our research and communicate even more directly about the risks of Zika. But this doesn't mean that we have all the answers. While the evidence supports a causal link, many questions remain. We don't yet know the risk from Zika infection during pregnancy. Although we know that Zika virus is the cause of Microcephaly and other severe brain defects, not all babies born to mothers who were infected with Zika virus during pregnancy will have problems. We need to learn more to answer this question. If a woman is infected during pregnancy, how often will her fetus have birth defects or other problems? We also don't know the risk to a fetus when a pregnant woman has symptoms of Zika compared to the risk when they don't have symptoms. We don't know at what stage Zika provides the highest risk. We don't know the actual range of potential health problems the Zika virus infection may cause. Does Zika cause defects other than those of the brain, does Zika cause learning problems later in life, are pregnancy losses, miscarriages, stillbirths among some women infected by Zika virus the result of the infection, and finally, are there other factors involved. For example, has another infection occurred at the same time as the Zika infection that might affect the risk of birth defects?
Answering these critical questions is the focus of our ongoing research and may help improve our prevention efforts and ultimately help reduce the effects of Zika infection during pregnancy. There is still more to learn about Zika and its link to other health effects like Guillain-Barre syndrome and other neurologic disorders. CDC is investigating the link which is very likely triggered by Zika in a small portion of infections. Much as it is after a variety of other infections. CDC is collaborating with local, national and international partners to analyze, validate and efficiently exchange information about the outbreak as we learn more about Zika, about how it is spread, and its effects on the public. We are committed to share what we know when we know it.
KATHY HARBEN: Thank you, Dr. Rasmussen. Operator, we're now ready to open up the line for questions.
OPERATOR: Thank you. If you would like to ask a question, please press star one on your touch tone phone and record your name clearly after the prompt and I will introduce you for your question. Again, a star one to ask a question. If you need to withdraw your question, you may press star two. One moment, please, for the first question. The first question comes from Mike Stobbe, Associated Press. Your line is open.
MIKE STOBBE: Thank you for taking my question. I had two actually. i wanted to clarify, is the CDC's statement that Zika causes Microcephaly alone or is it that it causes Microcephaly and other severe brain severe related birth defects, and what -- exactly which birth defects is it being named a cause of. And my second question was why declare this now? We’ve seen the evidence a couple months ago about evidence of Zika in spinal fluid, in brain tissue, and there are ongoing epi studies to try to establish more conclusively what happens if you -- i was wondering, why exactly now, why not wait.
SONJA RASMUSSEN: Yeah, mike, the first question, we are saying Zika causes Microcephaly and other severe birth defects of the brain. And that is what we've seen thus far is primarily things like intracranial calcification, other pretty severe brain defects that are seen. I think we don't know the full spectrum of that either, but we know it's not just Microcephaly. And the kind we're seeing in babies with Zika virus is a very severe form. and then the "why now" question, since the start of this outbreak since we first heard about the outbreak actually back in October, we began assessing the evidence and we started collecting the information trying to decide when could we say that Zika virus caused birth defects. we started about a month ago using these criteria looking each -- putting together the criteria and looking at which ones had been met and which ones haven't been met. We want to do it in a very careful and systemic way. We didn't want to say that Zika virus caused birth defects before we were really confident that that was the case. And so we used that framework and also Bradford hill criteria and we very recently presented this to our group of experts at CDC and the group agreed that Zika virus does cause birth defects based on those sets of criteria. After that, we felt it was important -- we could wait until it was an absolute assuredness, all the studies were in, but as Dr. Frieden said, that could take a long time that could take essentially years. And so what we decided is that we wanted to share what we knew when we knew it. And we felt now that the data are there, that the evidence are there, the pieces of information that we know right now makes us confident that the Zika virus causes birth defects. Certain types of birth defects. We still have a lot of questions remaining, though.
KATHY HARBEN: next question, please.
OPERATOR: the next question comes from Mark Remillard from ABC News. Your line is open.
MARK REMILLARD: thank you. Thanks for taking my question. I had two questions for you. First off, you mentioned that obviously the CDC surveillance video is still advising people to use condoms. Has anything changed with the CDC in the course of this research that shows whether the connection between this Zika being sexually transmitted, is that -- how sure is the CDC of that. And the second part of the question, is there any indication what the lasting effect of Zika virus might be. if someone were to travel to an affected country, get the disease and then come back, i mean are they -- do we know if they're running a risk of having a child years down the road with birth defects or anything like that, any light you can shed on that?
SONJA RASMUSSEN: Yes, so first of all, the question about changes in CDC guidance about sexual transmission, the information that we have today really doesn't have any change in our CDC guidance. We have been proceeding, we have been doing our public health action with the assumption that Zika virus causes birth defects. So there is no change in our guidance about travel or in our recommendations about preventing sexual transmission. So no change in that. about lasting effects years down the road, what our understanding is about Zika virus is that the virus is at risk when it's in the mom's blood and can transfer across the placenta to the baby. We expect years down the road the woman would have cleared the infection and her baby would not be at risk years down the road. But as we've said before, we’re always learning more about Zika virus. But that is the information that we have based on what we know from other viruses, other similar viruses.
OPERATOR: The next question comes from Helen Branswell, STAT.
HELEN BRANSWELL: I have a couple of questions. My first relates to something that mike asked but i kind of look at it from a different point of view. instead of why wait, i kind of -- you folks have been saying for a while now that this is -- there is really -- Dr. Petersen said it a month ago and WHO said it a couple weeks ago, too. So is there -- is this just sort of dotting the i’s and crosses the ts for the science or is there a public health reason for needing to say this clearly at this point?
SONJA RASMUSSEN: Yeah, I think why not earlier, why we didn't say something earlier, I think we really wanted to go through the systemic way of using a criteria using a framework, making sure that each one of those issues that in the shepherd's criteria was addressed. And just recently that information all came together. We also waited because we wanted to be able to have the paper peer reviewed. We didn't want this to just be something that was coming from CDC. We wanted this to be something that was representing the public health community and of course The New England Journal did send the paper out for peer review and we think peer review is important. So why is it important for public health? I think our messages will continue to be the same about travel and about sexual transmission. We do know at least surveys have told us that a lot of people aren't concerned about Zika virus infection in the United States, don't know a lot about it. And my hope is that now that we can be more convincing, that Zika virus does cause these severe birth defects in babies, that people will focus on our message and our prevention messages more carefully. It also helps us to focus our research and we know now that there are a lot of questions that we need to answer and we can focus on those questions.
OPERATOR: The next question comes from Donald McNeil, "New York times." Your line is open.
DONALD MCNEIL Hi, this is on the same theme. Having this pulled together and reviewed by in-house experts sounds awfully inside baseball. People will reach the conclusion that the boss wants them to reach. I know you had it peer reviewed by The New England Journal of Medicine, but that's not a very loud public process. The W.H.O. convenes a panel of experts and they had said that they wanted to see evidence of the prospective cohort study of thousands of women in Brazil and Colombia and elsewhere before they reach this conclusion. Why are you reaching it using just inside experts and not -- and did you coordinate with the W.H.O. to see if they agree with you?
SONJA RASMUSSEN: Yeah, I do think we went through a very careful process here. We used a very accepted framework, Bradford hill criteria, we used another framework used for many stratagems in the past. We went very careful through those frameworks and I think that is our role is to carefully review the science and then let the American people know what we're thinking when we're thinking it. So that's the process that we went through.
OPERATOR: The next question comes from Lena Sun from the "Washington Post."
LENA SUN: thank you very much. So i guess to follow up on what he asked then, this was not coordinated with W.H.O., right, and my other question was to what extent -- how recent are the studies that you looked at? because there have been a couple of things that have come out at the end of march that are very interesting about the way the virus works on -- how it attacks brain tissue, how long the virus stays in the blood of a pregnant woman. Were studies included up until like the end of March? Did you look at those?
SONJA RASMUSSEN: We included studies up until this past weekend. The New England Journal moved very quickly with this and worked very closely with us. And we were still making changes on Saturday, Sunday morning in the paper adding the most recent data that is available. So we did include very recent papers. Oh, about W.H.O., W.H.O. I believe had announced last Friday in their report that they have reached scientific consensus that Zika virus causes birth defects, as well. So i think we're on the same page with W.H.O.
OPERATOR: The next question comes from Lisa Schnirring of CIDRAP news.
LISA SCHNIRRING: Thanks for taking questions. Your list of questions that still need answers was long and daunting and very interesting. I’m wondering if you might be able to say which ones are the highest priorities would be good to know. Thanks.
SONJA RASMUSSEN: I do feel like one of the key things is knowing the level of risk. I think women who are -- especially women that are in areas -- we're hoping that women that are not in areas with Zika virus transmission actually don't travel to places and prevent getting Zika virus infection. For women who are in those areas, we realize this is a very scary thing. Zika virus infection is a scary thing and we don't know if the risk is somewhere in the range of one percent or in the range of 30 percent. So I think that's one of the key questions that we really want to answer. And we do have studies ongoing right now that we hope will answer those questions as soon as we possibly can.
KATHY HARBEN: Next question, please.
OPERATOR: The next question comes from Eben Brown, Fox News. Your line is open.
EBEN BROWN: Thank you very much for taking the call. A couple questions. one, what is the life expectancy of a baby born with Microcephaly, and the second question is, if we have a lot of children born in a certain part the world, in this case south America, Latin America, in cultures where prophylactics and birth control is not necessarily well taught or well advocated, do we have a risk of having a severe generational population loss going forward, I’m thinking maybe one or two generations if we have a lot of babies born that don't live long and then themselves don't procreate?
SONJA RASMUSSEN: To answer your first question about life expectancy of a baby with Microcephaly, I think we know a lot about Microcephaly and that it has a lot of different causes. We don't know a lot about Microcephaly that is associated with Zika virus infection and that's something that we're learning more about every day. From what we understand, it's a very severe form of Microcephaly, more severe than what we typically see as pediatricians in children that have Microcephaly. So it's a pretty severe form and we'll have to do some research studies to figure out what the life expectancy is of kids with that severe form of Microcephaly. The question about future generations, i think we're doing everything we can here and working with our international partners to as much as possible prevent having a generation of babies with these sorts of problems.
OPERATOR: The next question comes from Robert King, "Washington Examiner." Your line is open.
ROBERT KING thanks for taking my question. You referred a little bit about Guillain-Barre syndrome. Do you have any idea when you can make a concluding system about the link between Zika and Guillain-Barre?
SONJA RASMUSSEN: I’ll have Dr. Petersen answer that question.
LYLE PETERSEN: Yes, hi, this is Lyle Petersen. We currently have an ongoing study in Brazil looking at Guillain-Barre and we're collecting information here and in the United States and Puerto Rico as it becomes available. We don't have a definite time yet of which we can make a conclusive remark like we have for Microcephaly. However, I think we are very concerned about this both for Guillain-Barre and maybe other neurological problems that have been reported by others. And so because a number of countries who have had outbreaks have all reported increases in Guillain-Barre, we're quite concerned about this and this syndrome also occurs with other related viruses to Zika virus. So it's very plausible that we'll eventually be able to make a conclusive link between the two.
OPERATOR: The next question comes from Rob Stein, National Public Radio. Your line is open
ROB STEIN: Thanks for taking my question. I just want to clarify one point. So you're saying Zika causes Microcephaly and other serious brain abnormalities. Are those other serious brain abnormalities, do they occur sometime independently of the Microcephaly or is the brain damage that occurs with Microcephaly. And then my second question is, do you have any idea what the level of risk is for women who get infected during the first trimester or early in the second trimester? That’s obviously the next big question. I know you don't address this directly in this paper, but are you starting to get any kind of estimates?
SONJA RASMUSSEN: Okay. Thank you. So first the question about other serious brain abnormalities and whether some occur independent of Microcephaly. Our linkage, our linkage between Zika virus and Microcephaly and saying that it's a cause really is talking about Microcephaly that is associated with these other serious brain defects. However we do expect that that is likely to be the tip of the iceberg, that there are likely to be babies that won't have small head per se, but will have other types of brain defects. And your second question, any idea of the level of risk, the information that we have right now from epidemiologic studies ranges pretty widely. There was a study performed in French Polynesia that showed estimated using mathematical modeling and using serological data that the risk was about 1 percent of having a baby with Microcephaly. It wasn't looking at any other kinds of defects, just Microcephaly. But that is one place, one study, one estimate. There was also another study that was from Brazil that gave a much higher estimate, it was done at a different -- it was a different type of study. And it showed about almost 30 percent of women who had had Zika virus infection during pregnancy, any time during pregnancy, had an abnormality on ultrasound. And some of those babies have been born, some of those babies have not yet been born. So sometimes what we see in ultrasound isn't exactly what we see when the baby is born. So we're anxiously awaiting to hear what the results are, what those -- what kinds of problems those babies have when they're born. And there are a number of other studies. We’re working on some studies here which will help provide other information about that level of risk, too, and that is really a critical question for us right now.
OPERATOR: the next question comes from Weijia Jiang, CBS News. Your line is open.
WEIJIA JIANG: Hi, thanks for your time. This is a follow-up question on the long lasting impacts for women who are impacted. Before you said years down the road their blood should be cleared like you've seen in other viruses and therefore years down the road their baby will likely not be at risk. Can you be more specific about that? I mean how many years are we talking if a woman becomes infected when she's not pregnant and then, you know, becomes pregnant later on?
SONJA RASMUSSEN: Yeah, so based on the information that we know right now, about two weeks ago on march 25, we released an article in the MMWR that provided guidance for women of reproductive age. And in that, we made what i think is a careful estimate of the time that women should wait after they have either traveled or after they have been sick with Zika virus infection and the recommendation that we made was eight weeks. So based on the information that we have right now, and based on what we know from other infections, we expect that women will be able to clear the virus if they were infected and not have problems with their pregnancies if they waited that eight week time period. That’s based on the best information that we have right now.
OPERATOR: The next question comes from Jeneen Interlandi from consumer reports. Your line is open.
JENEEN INTERLANDI: Thanks so much for your time. You mentioned this a couple of times that the Microcephaly cases you're seeing with Zika is much more severe than you see in typical Microcephaly cases. Can you elaborate on that, how much more severe and is the actual presentation that much different? Thank you.
SONJA RASMUSSEN: Yeah, this is something that right now we have information detailed clinical descriptions available on a pretty small number of babies. But based on those clinical descriptions that we have on those babies, it looks like this is a very severe form of Microcephaly and it looks like something that has been called in the past fetal brain disruption sequence, a kind of abnormality where the virus can have a destructive effect on the brain. And some of the features that we see in babies and this is something that we're looking more at this time, but some of those features suggest that that is what this is. And that's what suggests that this is a more severe form of Microcephaly. Also even just the measurements of the baby's heads are much smaller than what we typically see in Microcephaly. And the kinds of neurologic problems that are being seen, severe swelling problems, problems with contractures of the joints, those suggest to us that this is a severe type of Microcephaly with serious brain defects.
OPERATOR: The next question comes from Lynne Peterson, "Trends in Medicine." Your line is open.
LYNNE PETERSON: Hi, i was wondering if there are any implications from this finding in the pursuit of vaccines or treatments for Zika. Does this change in any way the approach that should be taken?
SONJA RASMUSSEN: Sorry. Implications for the approach to Zika?
LYNNE PETERSON: so vaccines or treatments.
SONJA RASMUSSEN: I think this emphasizes the important of working on identifying ways to prevent Zika infection and vaccine is one of those key ways. So i think it emphasizes even more importance of developing a vaccine for Zika.
OPERATOR: the next question comes from Katie Leslie, "Dallas Morning News." Your line is open.
KATIE LESLIE: Thanks for taking my question. again, being I’m focused on what this means for Texas and I wonder if you can reiterate what a hopeful mother should be doing in terms of really specific prevention efforts, one, they cannot travel to Puerto Rico and use condoms, but should any be using powerful bug sprays? What are you advising doctors to tell them and then finally, can you reiterate the travel ban, what places would qualify for that considering Dallas has had a few cases of Zika at this point. Thank you.
SONJA RASMUSSEN: At this time in the 50 states, there have not been any mosquito-borne transmission of Zika virus. We do know that the mosquitos that can spread Zika virus – Aedes Egypti and Aedes Albopictus are found in many states in the United States. But at this point, there has not been any proven transmission of Zika virus by mosquitos in the 50 states. Of course there are in Puerto Rico and other U.S. territories as well as many other countries in central and South America and that whole list is on the CDC travelers’ website. So it's important that people are aware of that so they know about places to avoid traveling to. I think we know mosquito bites spread other diseases, as well. And so I think it's always important for pregnant women and actually for everybody to not get bitten by mosquitos. And so if you're in a place where you can be bitten by mosquitos, it is important to protect yourself. And whether that's wearing long pants or long sleeves or if it's hot and you don’t want to do that, I think the other alternative is to wear mosquito repellants. So that is an important thing. The other thing is thinking about the community. Mosquitos breed in standing water. And especially these mosquitos. Even very small amounts of standing water. And so it's really important to make sure that there isn't standing water that is a breeding place near houses for mosquitos to breed.
OPERATOR: The next question is from Megan Rosen, "Science News." Your line is open.
MEGAN ROSEN: Thank you. Are we seeing more babies with Microcephaly being born now in Colombia and did this factor into your conclusion that Zika causes Microcephaly?
SONJA RASMUSSEN: We took every reliable piece of information that we had to put together this analysis. And that did include that there are preliminary reports in Colombia of babies with Microcephaly. Whether all those babies that have been seen with Microcephaly have Zika virus, I don't think we know right now. But we do know Colombia had an outbreak for several months of Zika virus infection and based on what we've predicted, this is the timing that we would begin to see cases in Colombia. So we did consider that, those cases that have been seen there recently in this analysis.
KATHY HARBEN: We have time for one more question.
OPERATOR: The next question comes from Joette Giobinco, WTVT. Your line is open.
JOETTE GIOBINCO: Hello, I’m sorry, thank you for taking my question. I have kind of an unrelated question. I had been contacted by some individuals from Brazil and they had had some concerns about some deaths. Sounds like those deaths may have been related to either ADEM or perhaps Guillain-Barre, one, in particular, was a 37-year-old law professor. Do you know anything about the direct correlation with the Zika virus and deaths especially in Brazil?
LYLE PETERSEN: hi, this is Lyle Petersen. We have had no published information about these cases, so it's very difficult for us to determine exactly what happened in these instances. What I can tell you is that in a proportion of people who do get Guillain-Barre from other causes, a proportion of those people will actually die from Guillain-Barre. We cannot tell at this time what proportion that would be in Guillain-Barre that may be linked to Zika virus.