In Man vs. Virus, The Win Goes to the Swift

The executive director of the Consortium for Conservation Medicine explains that while zoonotic diseases like swine flu are increasingly with us, quick public health reflexes can successfully clamp down on the outbreak. A interview.
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The executive director of the Consortium for Conservation Medicine explains that while zoonotic diseases like swine flu are increasingly with us, quick public health reflexes can successfully clamp down on the outbreak. A interview.

A little more than a year ago, a team of scientists that included Wildlife Trust President Peter Daszak identified Mexico and other tropical locales as "hotspots" for emerging zoonotic diseases (diseases that can be transmitted between humans and animals, including the H1N1 virus).

In a paper published in Nature, the team made a predictive map of where diseases are most likely to emerge — Latin America, tropical Africa and Asia — and, for the first time, were able to correlate socioeconomic, environmental and ecological factors to disease risk.

Daszak has adjunct positions at three American and two British universities, and has served on committees of the International Union for the Conservation of Nature, the World Health Organization, National Academy of Sciences and Department of the Interior. His research focuses on the taxonomy, pathology and conservation impact of parasitic diseases. He is executive director of the Consortium for Conservation Medicine.

We caught up with Dr. Daszak by phone last week. What sort of analyses are you doing now?

Peter Daszak: We've been analyzing trade and human travel data information in and out of Mexico before and after the outbreak. What we've found is that it looks like Mexico imports hundreds of thousands of pigs every year for the pig industry. Often these swine influenzas don't cause huge critical signs in pigs, so it could go pretty much unnoticed. The other thing is that Mexico does import pigs from other countries in Latin America and countries in Europe - not many, but enough to bring over other strains. In terms of origins, it may be that this virus was hanging around a long time in pigs in North America as a region, switching genes with other viruses, and then the avian gene got inserted.

It seems it made the step into human disease in Mexico. The next question is how did it travel so widely so rapidly? The answer to that is through travel networks, which are incredible now. We've been tracking travel information, and we've found that a large number of passengers traveled to other Latin American countries from Mexico at that time. Some of those countries haven't reported many cases, if any. So I think we're going to see a bigger impact in Latin America as those cases get noticed.

They're probably not being noticed because they're not being reported. These are people who traveled to Brazil or Venezuela and went home, maybe to the countryside, and got ill and have not yet seen a doctor.

Mexico City is a hub for connections to Latin America. The volume of travel to Latin America from Mexico is huge. It's also a huge connector for people traveling from Houston, Miami and New York. The richer countries that can afford better health care are going to report the cases first. That's why we saw cases reported rapidly in New Zealand. New Zealand picks up cases very quickly because it's got better reporting and better health care. We should expect to see surprising numbers of cases from places like other parts of Asia, Australia and even Africa.

M-M: You noted in a recent article that your group will be releasing findings related to the H1N1 virus. When will they come out?

PD: We're doing a formal analysis and will publish a paper in a journal soon. What we've found is that once an influenza gets into a country like Mexico, it's going to very rapidly get into the U.S. We can't live in isolation now. We really have to look at what our neighbors do and make sure that the same standards of surveillance and control that we have we share with our neighbors or we pick up on their standards and control. It's countries coming together and working together as a unit — that's the way to beat these diseases.

M-M: It seemed that the word got out fast on this virus and steps were taken fairly quickly. Is that how you see it?

PD: The response did happen very quickly, but we should have seen this coming before it happened. We predicted it. We didn't say which virus and exactly when; you can't do that. What you can do, using the very sophisticated computers that we use, is you can say, 'Here's the hot spot.' It's the equivalent of an earthquake zone.

If you live in an earthquake zone, like San Francisco, and you're building a house, you build it to code and that code includes protection against earthquakes. In the same way, if you're in a disease hot zone, and you're building a pig farm or poultry trade or you're increasing travel, you need to build in protection, and the protection you build in is surveillance. The surveillance wasn't up to snuff when you compare it with what we do here in the U.S.

M-M: Do you think the virus originated in the large hog-farm operations in Mexico?

PD: When we look at the data on the hog trade to Mexico, it's increased pretty dramatically in last few years. I don't know why, but it feels like this is (due to) stocking of big pig-farm production facilities. There's nothing wrong with that. As a carnivore, it's great to have cheap, good-quality food.

But the problem is that part of the risk of doing these trades and these globalized food production networks are disease outbreaks. When we do globalized food production and trade, we've got to insure ourselves just like you would insure yourself personally if you were doing a high-risk activity — you'd make sure you have life insurance.

Diseases are an actual product of these things that we do. For the first time ever we were able to prove that scientifically. Human activity drives the emergence of new diseases. Everybody says it, everybody thinks they know it, but we were actually able to show it definitively. The message there is that human activity is a risk for disease emergence so let's insure ourselves properly against that risk. You can still do the trade. There's nothing wrong with intensive production of pigs per se, but you've got to be careful when you do those things. You've got to get ready for those diseases.

M-M: Can you give an example of the sort of surveillance or testing that's needed?
PD: It's probably not fair to pick on the pigs too much because there is a question of if this really came out of the pig farms in Mexico. The point is there's swine involvement. Now, what you would do is in a hot zone — like Mexico, like South America, like Southeast Asia, any large animal production facility — there should have a higher level of surveillance. And that means testing more animals for more pathogens.

I'll give you an example of how poor our strategy is to protect ourselves against disease. We published a paper in Science this week on the wildlife trade. When animals come into the country in the U.S., we think we're protected. We test pigs, sheep, cows; we test them for four or five diseases only. We don't test for rare diseases or for pathogens we don't even know about. In the wildlife trade, 200 million animals come into the country every year. Most of those come in without any testing at all.

M-M: Really — that many animals?

PD: It's mainly fish, so that's not a big risk. Actually, there are zoonotic diseases that fish can carry. There are also mammals in there, birds in there. Birds are tested for three diseases: psittacosis, which is a rare disease that comes from parrots and can affect people, Newcastle disease, and only in the last few years, avian influenza. What about all those other diseases — for instance, West Nile disease? We know that West Nile emerged in the U.S. recently. It first started in New York. It clearly came in to New York through trade or travel. Humans can't carry it because we're unable to spread the infection. But birds can, mosquitoes can. Who's checking those animals that come in for things like West Nile? Nobody. Who's checking airplanes to see if they've got mosquitoes that are bringing it into the country? Nobody. There's big gap out there that's not being covered.

M-M: Can you give me some examples about how socioeconomic and environmental factors affect the emergence of disease?

PD: Sure. A good example is we've found that the origin of SARS (severe acute respiratory syndrome) is bats, a group of viruses carried by bats in Asia. People of Asia eat bats. What's happened is that the population of Asia has increased, especially in Southern China. The prosperity of people has increased and they can afford these special meals of wildlife. So the trade in wildlife increases and you get these animals coming together in markets where different species are mixed and people live in those markets. So it's a perfect place for pathogens to spill over from bats into people.

Another good example is deforestation. If you've got an intact forest full of wildlife, the wildlife carries viruses that don't really affect them. If you build a road through the forest to log it, you bring in camp workers who are doing the logging. They start to eat wildlife or they're exposed to wildlife, and you start to see the pathogens spilling over into people. So any disruption like that brings in the risk of disease spread.

M-M: It seems to come down to the world being smaller and there being more people.

PD: It does. It's a human-driven thing. Human population is in strong correlation with emerging diseases. But it's not just the denser the city, the more risks there are. It's really what people do. The more people you have in an area, the more resources you need; the bigger the food industry, the bigger the deforestation, the bigger the urban sprawl — all those things have a risk of disease spread. Now, the answer to it doesn't have to be we can't do anything about it because human population is expanding. We can expand in a smarter way, in a way that won't leave us wide open like this — and start to do surveillance that really gets to these big issues and target the areas where these diseases are emerging rather than doing this randomly.

So, if you're a government with $2 billion to spend on surveillance, don't spend it all here in the U.S. necessarily. Put some funds into those areas where these diseases originate and try to block them before they emerge. Look at wildlife in those regions - see what pathogens they carry. The idea here is that it's effectively cheaper because you stand a better chance of preventing a disease from going to people and therefore the outbreak is smaller and the cost in terms of human lives and economic costs is a lot less. It's economically a better move. The argument is pretty strong for governments to do this.

M-M: From reading your paper, a person might surmise that you would suggest stopping flights into the United States and Mexico because these countries seem to be the epicenter of the H1N1 virus. Is that correct?

PD: The real problem in this outbreak is that whatever we did when we found out was already too late. I think the real trick is to be massively increasing our surveillance, working with Mexico, working with other countries in hot-spot regions — Brazil, African countries, Asian countries — and saying, 'Let's share technology, let's share resources,' so that they benefit as well, and they see the value of allowing us in. That way, you get the disease much quicker, before it even leaves the country. Then you don't have any of these ethical dilemmas about whether you cancel flights or quarantine people, like China had to do. We need to be targeting our resources in a smarter way. We've been calling this 'smart surveillance.'

M-M: But it seems that by the time they identify a virus, it's too late no matter what.

PD: No. If you get it in the first case, you can control it. If you get it in the first cluster of cases you can control it. If you get it in the first city, you can control it. The problem happens once it's spread out in the travel network.

A good example is we've been working in Bangladesh for the past few years and there's a virus there called Nipah virus,  which is very lethal; 70 percent of people who get infected die. It spills over from bats into people every year, and you get small clusters of cases — a dozen cases, a hundred cases. We're really concerned because it's got the ability to move from one person to another, so it has the potential to become a pandemic.

Bangladesh is the densest population on the planet. People are traveling there in increasing numbers every year, so we're there working with teams trying to find ways of stopping the virus spilling over in the first place — testing bats, working out what time of year is the highest-risk time, what activities bring people into contact with bats. To do that costs a few million dollars. If there was an outbreak that spread beyond Bangladesh, first of all, you've got a large number of lives lost. You've also got an outbreak that shuts down travel and industry and will cost tens of billions of dollars. I just think it makes sense on a public health and economic front.

M-M: Is that an example where you've been able to contain a virus?

PD: It's still research right now. There are strategies to stop people from getting infected. There are no drugs, no vaccines. It's a very dangerous pathogen. Right now we're in the early stages of it becoming a pandemic, so we'll hopefully prevent it. And that's where we need to be with all these diseases. We need to be much smarter in the way we do our research. We need to get out there before they emerge and try to block them — even when they're still in wildlife.

M-M: Could you immunize wildlife?

PD: We're a conservation group, so we're always very nervous about doing things with wildlife. But in some cases we do that. If you look at raccoons, in the U.S. we vaccinate wildlife. We throw out edible bait that only gets into raccoons and stops them from being infected (with rabies). A simpler way is to stop people from getting in contact in wildlife, to educate people who eat wildlife, to talk to people who have pet trade in wildlife and find healthier ways to do captive breeding in a pathogen-free way. There are lots of things you can do. But the bottom line is you're dealing with human behavior, trade, economics, and you have to find a way that people will want to do. And that often involves a way that doesn't lose them money.

M-M: When you're dealing with a developing country, that's a major concern.

PD: It is. That's the other unfortunate thing about this disease. Now, Mexico is a wealthy country; it's doing very well economically. The pig industry is critical to that country's growth, and it's unfortunate when a country loses travel and trade because of this. It's very hard to say to a country, 'developing this agricultural network is going to put you at risk of disease,' so we need to work to find simple and cheap ways to stop that. And surveillance is pretty cost-effective. It just involves testing animals and testing more of them. It adds some extra dollars to the cost of a pig. It's cheaper than an outbreak, that's for sure.

One of the real problems of surveillance is it goes against human nature. Human nature is to respond to an outbreak, to respond to an earthquake, to send all our resources in to help people who are suffering. Political will and human nature say, 'Why would we put a lot of money and energy into prevention that ends up with no result — nothing happens.'

The question is, what can you show people? We're working on ways to do that. We have some economists working with us who are analyzing the wildlife trade and travel — the true cost of these diseases and who should pay for it.

M-M: There's also increasing reports of transference of disease from humans to animals, isn't there?
PD: There's evidence of polio in chimps in Gombe in National Park in Tanzania; there's been influenza from people in gorillas; there's human nematodes in gorillas. It's a consequence of ecotourism. So we do things we think are going to be good. We have ecotourism programs to bring in dollars to help save species and one of the outcomes of that is that diseases from us get into wildlife. And it's very easy to stop — better control of tourists, better sanitation, not letting sick people go near the gorillas, not touching them. There are policies in place to stop that.

And if you think of the big diseases that had the highest impact recently — HIV, Ebola, Lyme disease — they're from wildlife, so there clearly is an issue that wildlife carry these pathogens. Our message here is don't blame wildlife. It's what we do with wildlife. If we leave wildlife alone in protected areas, there should be no problem. Environmental degradation is one of the causes of emerging diseases.

M-M: That sort of transference probably happens more than we know.
PD: I expect it does. With all of these disease issues, there's a lot more going on than we hear about. For instance, we know this virus in Bangladesh ... first emerged in Malaysia in 1998. We work in Malaysia. We heard about unusual things happening in Bangladesh and sure enough, it's in Bangladesh. And then we did some analyses of outbreaks of unknown diseases in India and we tested animals in India and sure enough, the virus is there, too. These diseases are increasing in number year after year, decade after decade — new diseases spilling over into people. Even if you correct for more and more scientists trying to find them, we're still seeing an increase, dramatically.

M-M: Will developing countries likely take the brunt of these outbreaks because of lack of access to flu shots and other medicines?
There was a good bit of research couple years ago that suggested Thailand could be the source of the next avian flu outbreak, and if you had 12 million doses of Tamiflu, you prevent the outbreak from getting out of the country. And sure enough, World Health bought 12 million doses of Tamiflu and donated them to Thailand. So people are trying to work to protect the globe from diseases in emerging countries that can't afford as good a health care. The other message is that the things we do here make us a hot spot, too. High population density, lots of changes to the environment, changes to food production — these are big risk factors for emerging diseases.

M-M: What predictions would you make today?
PD: Globally, we're going to see a lot more of these emerging diseases - more diseases coming from wildlife. They're going to emerge in the tropical regions of the world where all the wildlife are, especially in those countries where there's high wildlife diversity and big populations of people changing the environment. Mexico is one of those countries — a huge human population, lots of diversity, lots of changes to the environment and food production. So (they will emerge in) places where economic change is happening very rapidly — India, for instance, where people are getting wealthier quicker. They're changing their livestock production strategy, and we'll see new diseases emerge through that. I firmly believe we can predict these things, and I firmly believe we can prevent them, too.

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