Mosquito-transmitted Zika virus has arrived in Central and South America, and while most people are not affected by it, the virus has been linked to microcephaly, a severe birth defect. Experts discuss the virus, how it’s transmitted, its spread to the US, and how to protect yourself from it.
- Dr. Uriel Kitron, Professor and Chair of Environmental Sciences, Emory University
- Dr. William Schaffner, Professor of Preventive Medicine and Infectious Diseases, Vanderbilt University Medical Center
- Dr. Anna Durbin, Associate Professor of International Health, Johns Hopkins Bloomberg School of Public Health
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16-08 Zika Virus
Reed Pence: Three or four years ago, most Americans had never heard of Ebola. The epidemic in West Africa in 2014 quickly changed that, though only a handful of cases ever made it to our shores. Now there’s another international public health crisis we need to pay attention to: Zika virus. Dr. Uriel Kitron is professor and chair of environmental sciences at Emory University.
Dr. Uriel Kitron: It’s clearly quite a big deal. I don’t think that is the case because we’ll have a big outbreak and transmission in the continental United States, but it’s a big deal because it has now spread through much of Central and South America and the Caribbean, including Puerto Rico and the US Virgin Islands I want to mention. And it’s quite likely it will move back to Asia and possibly Africa as well.
Pence: Now if you think Zika virus seemingly came out of nowhere, you’re right. Only a few virologists were really familiar with it until recently, according to Dr. William Schaffner, professor of preventive medicine and infectious diseases at the Vanderbilt University Medical Center.
Dr. William Schaffner: Zika virus is, until recently, a rather unknown virus that was active in the South Pacific, but it was introduced into our hemisphere, into Central and South America and the Caribbean, where it has spread widely because it is transmitted so readily by a mosquito. If a mosquito bites an infected person, the mosquito gets infected itself and then can bite others. So it has spread very, very widely throughout the Caribbean, Central, and South America.
Dr. Anna Durbin: It’s very closely related to the yellow fever virus and dengue virus and West Nile virus, which people in the United States may be more familiar with.
Pence: That’s Dr. Anna Durbin, associate professor of international health at the Johns Hopkins Bloomberg School of Public Health. She says there’s a lot we don’t know about Zika virus because it’s relatively new.
Durbin: It was recently discovered in 1947. Tt was found in a jungle in Uganda in a monkey, so it came from monkeys and it’s in the jungle generally thought to be transmitted by mosquitoes to monkeys and then back to mosquitos. And the over the course of the past 50 or so years, it has gone from mosquitos into humans.
Pence: For most people, Zika virus isn’t dangerous. In fact, Schaffner says the vast majority of people infected with Zika virus don’t get sick at all.
Schaffner: The current estimate is about 80% of people don’t develop any illness, so it’s kind of ‘ho-hum.’ Now in the other 20%, they get a transient illness. Several days, maybe up to a week, of fever, kind of aches and pains in muscles and joins, not feeling so well, a rash, and red eyes. That’s uncomfortable for several days, doesn’t look so good, but it goes away and it’s harmless.
Pence: However, for two groups, Zika virus can be devastating and that’s what’s turning it into a public health crisis. The first of these two consequences can happen to anyone who’s infected, though it’s apparently fairly rare.
Schaffner: Anybody can get a consequence of this virus, which is called Guillain-Barré syndrome, which is a paralytic illness. Usually temporary, the person gets paralyzed and then the paralysis recedes, but during that period of paralysis which can last weeks, it’s kind of an awful illness and people frequently require intensive care.
Pence: The second consequence is much more alarming. It appears that pregnant women bitten by an infected mosquito are especially at risk.
Schaffner: The virus can get through the placenta into the baby and cause fetal damage. That’s what we think at the moment. And the specific fetal damages that the baby can be born with are a small head and a correspondingly small brain, so-called microcephaly. Sometimes these babies can normal function and personality but all too often, they have impediments that last throughout their life. So it’s a very tragic event.
Pence: Durbin says since Zika arrived in Brazil a year ago, there’s been a sharp increase in reports of microcephaly.
Durbin: The Zika outbreak started in Brazil- April, May 2015, and then in the fall of 2015, Brazil reported increased numbers of cases of microcephaly. So the timing of that makes it very suspicious that Zika virus caused it; that these young mothers who were in their first or second trimester back in April, May, or June were infected with the virus and then when they delivered the baby in October, November, found microcephaly. So the timing is very suspicious. Unfortunately, it’s been very difficult to confirm that length. Pregnant women in these countries are panicking and causing a lot of anxiety understandably. It’s so important that we really try to understand this and understand whether or not the link is true. In addition, I think, we need resources to better understand the virus. There’s a lot of unanswered questions.
Pence: Unfortunately, if a pregnant woman is bitten, Schaffner says there’s not much to be done but watch and wait. There are no treatments.
Schaffner: Particularly if women have had an illness, a Zika-like illness when pregnant, the current recommendation is that they be followed carefully and have periodic ultrasound examinations of the developing baby, so that if there is microcephaly, that diagnosis can be made while the baby is still developing. There are all kinds of complicated because microcephaly, among other things, is usually diagnosed fairly late.
Pence: In most South American countries, termination of a pregnancy is illegal if a woman’s life isn’t in danger. But Schaffner says Zika virus has forced re-evaluation.
Schaffner: This is one that the countries of Central and South America are wrestling with. They’re obviously heavily Catholic countries and there is a strong social and religious prohibition against abortion. So this has become very much a matter of discussion once again in those countries.
Pence: But what about the risk to pregnant women in the United States? Schaffner says travelers are by far most at risk.
Schaffner: If you are a pregnant woman, or someone trying to become pregnant, this is the time to reconsider the importance of this trip. Because the potential effects on the baby, the developing baby, are so severe. So I have been recommending when I’ve been called recently that if you’re pregnant, have your vacation elsewhere or reconsider how you can conduct business if you’re going on a business trip. Perhaps you can do it remotely from home. Others need to take precautions against getting mosquito bites. Use insect repellent, long sleeves, long pants- doesn’t sound like so much fun in the tropical environment but that’s what you should do. And spend as much time indoors as possible.
Pence: A travel scare couldn’t come at a worse time for Brazil, which will be hosting the Summer Olympics in six months and had expected the world to attend. Now some nations are threatening to not send an Olympic team at all because of Zika. But Kitron says the worst of the crisis will have passed by then.
Kitron: One thing that could alleviate some of the concerns is that the Olympics are during the winter months in Rio, which are somewhat cooler and, more important, dryer which means it’s a very low transmission season. So fewer mosquitos around and the danger, for example, is going to make it much less than right now, for example.
Pence: Despite that, if a woman travels to Brazil or other countries where Zika virus is present, experts advise that she wait a month after arriving back home before trying to become pregnant. However, it’s possible and even likely, that Zika will make its way north to the U.S. Schaffner says public health experts are concerned because the threat is real. However, he and Kitron say the risk is relatively low.
Kitron: If we talk about the continental US, I think the beast comparison is to dengue, carried by the same mosquito, a closely related virus, which has not been a huge problem in the US- one localized outbreak in Southern Texas and Florida. I would think for the same reasons that the best vector mosquito, the aegypti, is found primarily there, those are the areas at highest risk for limited outbreak. A lot of it has to do, you know, with living conditions, environment. Staying in homes, etc. provide some protection.
Schaffner: We do have the Aedes aegypti mosquito in the United States, particularly in the Southern tier of states, but it’s in other parts of the states also. However, we in the United States spend most of our time in enclosed space- in homes that have windows, doors, and screens, and are air-conditioned. Obviously we go out a lot but we spend most of our time indoors and we try to keep those spaces mosquito-free, so that’s a great advantage we have. Number two, we have ready-access, most people have sufficient funds, to get insect repellant and indeed, insecticides that can be used on themselves and in and around the house.
Pence: Some Brazilian scientists reportedly believe that Zika virus has crossed over into the much more common Culex mosquito, which outnumbers the currently infected Aedes aegypti mosquito 20 to one. Kitron believes that’s very unlikely. But both he and Durbin say the tiger mosquito carries more possibility.
Durbin: That mosquito is far more prevalent in the United States. In fact, on the eastern seaboard it can be found as far north as Connecticut, so if that mosquito were able to transmit Zika quite readily, then what that means is there would be a larger part of the United States that might be susceptible to transmission. And if that is the case, certainly would cause us to re-evaluate. It may increase the risk of ongoing transmission in the United States. We do know, for instance, that dengue is not transmitted nearly as well by the Aedes albopictus mosquito and most of the mosquitos, or most of the mosquitos that have been found to carry Zika, are the Aedes aegypti not the Aedes albopictus.
Pence: But even though mosquitoes are the main worry when it comes to Zika virus, now there’s apparently one more way it can be transmitted.
Schaffner: Men, apparently, some men who’ve had Zika infection and recovered can still transmit the infection sexually to their partner. We don’t know whether this is frequent or not, or whether it’s quite rare. We don’t know how long after the Zika infection this can be potentially a problem. We don’t know whether it can work in the reverse direction. Can a woman transmit the infection to a man? So all of those things are things we are now learning about and people clearly who have had symptomatic infection, fellas, aught on returning home, use a condom during sexual intimacies because we think that this virus can be indeed transmitted sexually, but we still don’t know how long.
Pence: There’s no vaccine for Zika virus, but with the World Health Organization declaring a crisis, work is underway. Schaffner says we have experience with similar viruses such as West Bile, but some health officials characterize their efforts as trying to do two years of work in two weeks. CDC experts say phase one tests on a vaccine could be started before the end of the year, but Durbin admits even that leaves a finished vaccine years away.
Durbin: There will be high level meetings at WHO that will involve experts from FDA and other regulatory authorities to try to figure out how we can accelerate vaccine development and really get a vaccine, maybe not licensed for everyone, in two years or three years, but a vaccine that can target young women before they become pregnant and then expand your testing from that, over subsequent years. Because really the key is to get young women, preferably adolescents or young children, get them vaccinated early so that they have protection, they have immunity before they become pregnant.
Pence: In the meantime, that leaves personal protection–using DEET, long sleeves and window screens–and municipal mosquito abatement as the principal means of preventing the spread of Zika virus. Our experts say that in the United States, we’re pretty good at those tasks. But especially if the virus spreads north, it will become critically important.
You can find out more about all our guests on our website, radiohealthjournal.net. You can find archives of our segments there as well, and also on iTunes and Stitcher. I’m Reed Pence.
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