Americas Brace for Zika Spread

11:46 minutes

Zika virus is transmitted by a specific mosquito called Aedes aegypti. The mosquito is common in Colombia and other countries where Zika has become prevalent. Photo by James Gathany/Centers for Disease Control and Prevention
Zika virus is transmitted by a specific mosquito called Aedes aegypti. The mosquito is common in Colombia and other countries where Zika has become prevalent. Photo by James Gathany/Centers for Disease Control and Prevention

Since October, northeastern Brazil has been devastated by a wave of microcephaly, a condition where babies are born with abnormally small heads and damaged brains. At this moment, all signs point to the mosquito-borne Zika, a little-studied virus normally associated only with rashes, fever, and other mild symptoms. In the months since Brazil sounded the alarm, Zika cases have been popped up in a dozen other countries, and health authorities predict the virus will spread across the Americas. Infectious disease specialist Michael Osterolm explains what’s known about Zika, and what we can expect as this outbreak unfolds.

Segment Guests

Michael Osterholm

Michael Osterholm is Director of the Center for Infectious Disease Research and Policy (CIDRAP) at the University of Minnesota in Minneapolis, Minnesota.

Heard on the Air

How Scared Should You Be About Zika? (New York Times editorial, by Michael T. Osterholm)

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow. Since October, Brazil has had over 3,000 suspected cases of microcephaly, babies born with abnormally small heads and damaged brains. The main suspect, a little known mosquito borne virus called Zika. Zika cases have now been reported in over a dozen countries. And health authorities predict that as many as four million people will be infected throughout the Americas this year. So where did this virus come from? And what can we expect as the outbreak unfolds? How can we fight it?

Michael Osterholm is Regents Professor and Director for the Center for Infectious Disease research and policy at the University of Minnesota. He joins us today from St. Paul. Welcome back to Science Friday.

MICHAEL OSTERHOLM: Good afternoon. Thank you, Ira.

IRA FLATOW: What did we know about the Zika before this outbreak?

MICHAEL OSTERHOLM: Well actually, we knew quite a bit. But unfortunately what we knew wasn’t enough. We knew that this virus surely was capable of infecting humans. It was first discovered in Uganda back in 1947. At that time, primarily a virus that was really affecting monkeys and mosquitoes, not us. We saw it move through parts of Asia in the 1990s. And then in 2007, it actually caused an outbreak in the island of Yap in Micronesia.

And then in 2013, it caused an outbreak in the French Polynesian islands, which actually was the first time that we saw these severe symptoms, this microcephaly, or children born with very small heads and diminished brains, as well as potential Guillain-Barre Syndrome, a type of paralysis that occurs usually as an autoimmune condition. And so at that time, that was really the first warning to us that this could be serious. And then of course we knew that we were vulnerable to this in the Americas because the kind of mosquito that carried this virus actually was at an all time high in populations in the Americas.

IRA FLATOW: And that mosquito, what was it called? The Aedes aegypti?

MICHAEL OSTERHOLM: Aedes aegypti. Aedes aegypti is actually a mosquito that came over with the first settlers to the Americas. We brought it here as a quote on quote “invasive species”. And then it proliferated quite nicely right up through the 1940s and ’50s. And then a concerted international effort by the Rockefeller Foundation, the Pan American Health Organization, country governments, and Central and South America, and the Caribbean almost eliminated that mosquito from the Americas.

And then, when those programs stopped in the 1970s in conjunction with now the garbage world that we live in with the increasing non-biodegradable garbage that we have in our towns, villages, countryside, which now becomes ideal breeding habitats for that mosquito, saw an explosion of this mosquito. And today it’s at an all time high. We have more places with Aedes aegypti mosquito at higher levels than we ever had in history.

IRA FLATOW: So what has changed in the past few months that caused this outbreak in Brazil?

MICHAEL OSTERHOLM: Well actually, it’s not so much that the conditions change on the ground. First of all, this Aedes aegypti mosquito that I mentioned to you actually must be kind of looked at like the Norwegian rat. It basically loves to live with people. It’s an evolutionary advantage to it. It lives in water vessels in areas that don’t have running water where you have to collect it. It lives in cisterns. More importantly, it lives in garbage. One rubber tire or a plastic that doesn’t disintegrate, even throwaway wrappers that are in the ditches are all wonderful breeding sites for this mosquito.

The other thing that it has as an advantage is it’s a daytime biter. It doesn’t bite at night. And it actually has acquired the evolutionary ability to bite us from behind. It knows not to come in to the front of us. So it will bite the back of your ankles, your neck, your elbows. And you don’t feel it biting. And so, in a sense, it’s kind of the perfect stealth mosquito for transmitting these viruses. So we knew that that was there. And we knew it was in very high levels. It was causing outbreaks of dengue fever and dengue hemorrhagic fever.

In 2013, another virus, chikungunya, was introduced into the Americas in St. Martin and spread across the Central America, the Caribbean, and northern South America literally within two years. So we knew we were primed and ready for something like this to happen. I have been giving talks for several years saying it was just a matter of time before Zika would arrive.

What we didn’t understand was would the conditions that we saw in French Polynesia, this very severe microcephaly and Guillain-Barre Syndrome occur, which unfortunately it has. And so now we’ve got this virus in mosquitoes as well as the chikungunya virus and the dengue virus.

IRA FLATOW: There was talk that it was helped to be spread by sporting events that were occurring here in Brazil.

MICHAEL OSTERHOLM: Well, you know, we live in a world today where we’ve eliminated oceans, mountain ranges, and the biggest canyons, and clearly political borders as ways of stopping microbes. Three billion people crossed international border last year in travel. And so part of it is today it’s just like if you’re living here in Minnesota, where we’re always worried about the quality of our many lakes and aquatic invasive species from around the world, we’re doing that with microbes. We’re doing that with insects.

And so it’s not a surprise. It was just a matter of time. And the conditions were ripe in the Americas. And frankly, they’re ripe again in Africa and parts of Asia to see this emerge in those areas too. So it shouldn’t have been a surprise to us. What I’m worried about though is that we won’t take the steps necessary to really deal with this.

And it’s going to basically be about cleaning up the garbage of the developing world, and particularly in the Americas. And unless we do that, we’re going to continue to see this ongoing transmission, these wonderful pictures of people out spraying, fogging areas will surely kill the adult mosquitoes in many cases. It won’t touch, in many instances, the actual breeding mosquito in these kind of habitats where they breed. And so we really have a lot of work ahead of us to stop this.

IRA FLATOW: We here in the US are certainly part of the Americas. Is it going to arrive here on its own? I know people, there are cases of it being brought in.

MICHAEL OSTERHOLM: Yeah, thank you.

IRA FLATOW: Is it going to breed here?

MICHAEL OSTERHOLM: Yeah, one of the key issues here is this particular disease is one where it’s a mosquito human combination. Other vector borne diseases, or diseases transmitted by mosquitoes and ticks, actually require an animal species to be involved. In this case, you have to have an infected human, which an uninfected mosquito will feed on that human. They then become infected and they take additional blood meals on other humans where which they then transmit the virus.

So one of the things is when you have what we call basically an immunological virgin population, where we have no immunity, it’s going to ramp up and spread quickly. The second part of that is where do the mosquitoes exist? And in the United States we do have Aedes aegypti, mosquitoes, particularly in the southern states. There’s 12 of them primarily in the southeast. But the populations are much lower. We also have screens, air conditioning. And so it wouldn’t be impossible to have some activity here. In fact, we saw some in southern Florida, the chikungunya last year where it was brought in in a very similar manner. But we won’t have the same problem.

Now what concerns us, however, is that there is a new mosquito called Aedes albopictus, which is the Asian Tiger Mosquito. This came to the North American continent in the 1980s in truck tires from Asia and now has spread to over 30 states. This one actually right up into Minnesota here. If, in fact, that were ever to be capable of transmitting this virus, that would really be a game changer. So far we don’t have evidence that that’s occurring in South America, Central America, or the North America. But that’s one that we’re concerned about. And that could fundamentally change the game in North America.

IRA FLATOW: When you say you’re concerned about it, is there a real threat to the States? Or is it just a matter of time until it gets here?

MICHAEL OSTERHOLM: Well, I don’t think there’s a real threat to the States at all. We will have isolated pockets of cases, potentially particularly in the southern states. I think southern Florida, along the Gulf Coast, along the border in Texas, we surely could. We’ll get in and stop those quickly. This is not the same as we see in Central and South America. You know, we all live in a quote on quote “garbage world” in the sense of solid waste. But we do a much better job of managing solid waste in this country. We have the capability of responding more.

So surely, we could have clusters of cases. But not the widespread outbreaks that we’re seeing there. Our biggest concern is people traveling there. I mean, right now, this is the time of the year when people go to the Caribbean. And I must say, I really congratulate the Centers for Disease Control and Prevention on their very proactive recommendations about telling pregnant women, or women potentially becoming pregnant, not to travel to countries right now with the Zika virus infection. And I think that is a very prudent and thoughtful piece of advice.

IRA FLATOW: Is there a race now to come up with a vaccine against this?

MICHAEL OSTERHOLM: Well, there is. Everything is always about a vaccine. And one of the problems is that we always seem to be behind the game. I actually have an opinion piece coming out in the New York Times Sunday which addresses that issue in some detail. And one of the problems is I co-chair an international group right now looking at Ebola vaccines. And, you know, now that basically the international attention is no longer on West African Ebola, we have some real concerns about will we bring the Ebola vaccines across the finish line? And is there going to be a market for them?

Because again, we’re at risk of another Ebola outbreak in Africa like they had in West Africa. And we tend to go from crisis to crisis without ever anticipating it in advance and then completing the job in the end. And so I don’t know if we’re going to have a commercial interest in helping to develop these vaccines and what that will mean. It takes millions and millions of dollars. And if there is no return on investment at the end, it’s not there.

I also have one other concern about the vaccine, which I, again, very much support the work needs to be done. But one of the conditions we’re seeing, as I mentioned earlier, in this outbreak is a condition called Guillain-Barre Syndrome. Some of your listeners are going to be old enough to remember the old swine flu Guillain-Barre Syndrome connection back in 1976. And we’ve had other infectious diseases that also are related to this. And what happens is once you become infected, there is an immune response from the host, the person who got infected, that actually attacks the covering of the nerve in your body. And so it’s an immune response type of disease.

And that can be very serious. You get to the point where some people they can’t breathe because the muscles that basically control their respiratory system are no longer receiving the signal to fire. And that’s a serious issue. We would be concerned here if the disease could do it. Can a vaccine do it too? So we’re going to have to be really careful here to make sure that this is a safe vaccine and that we don’t actually involve risk in terms of Guillain-Barre Syndrome.

IRA FLATOW: I’ve got just a couple of seconds left. Do you have a prediction for the next outbreak of a disease?

MICHAEL OSTERHOLM: Oh, boy. I think there’s any number of them. The one that scares the hell out of me, and literally does worry me is the influenza pandemic issue. We have seen more activity in avian bird flu viruses in the past two years than we’d seen largely in the past 40 years. It’s just a matter of time before we have a really big influenza pandemic.

And our current vaccines today are grossly inadequate to provide the protection that we need. We need a game changing flu vaccine. We have a number of candidates, but nobody has built the runway for those candidates to take off yet. We don’t have any of them in studies that would get us close to a game changing flu vaccine. We’re still doing with the 1940s technology. That’s the one that scares me. Influenza could literally kill hundreds of millions of people in a very short order. And we’re not ready.

IRA FLATOW: Thank you very much for the warning, Dr. Osterholm.


IRA FLATOW: You’re welcome. Michael Osterholm is Regents Professor and Director of the Center for Infectious Disease research and policy at the University of Minnesota.

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