Zika has gotten a lot of hype lately with the recent Olympics being held in Rio de Janeiro, Brazil. Zika is a virus transmitted to humans mainly from the bite of a very specific species of mosquito – the Aedes aegypti mosquito. This species is found in tropical or subtropical zones, and Zika originated in Uganda in a rhesus monkey. It’s assumed the A. aegypti bit the monkey, and then has been spreading it ever since.
The second largest outbreak in the world has been in Brazil. That’s a long way from Africa. Experts are looking at how over 1,000 cases of the virus have occurred in Brazil, and some of the main causes are people inhabiting wildlife areas and being able to travel quickly and easily.
The symptoms of Zika mimic a mild flu – so why the big hoo-ha? Well, a couple of reasons:
1. Zika can be transmitted from human to human through blood or semen, and that gives it the potential to lead to a full-on pandemic.
2. It can cause pretty serious birth defects to a pregnant woman and possibly even terminate a pregnancy.
3. It’s recently being linked to cases of the nervous system disorder Guillain-Barré
I just finished researching and writing for a new TV series on AHC called How The World Ends. One of the episodes I worked on looked at the possibility of pandemics bringing the world to its knees. Zika came up, but like most people, I’m thinking, okay, spray a little deet on, don’t head south if you’re pregnant or thinking of becoming pregnant, and use a condom. Other mosquito-spread diseases like Dengue, West Nile and Malaria seem far more dangerous to me.
But one of the most interesting things about working on the doc series is that EVERY expert said we’re ignoring or underestimating the impact of Zika. Zika isn’t only causing severe birth defects, but it’s possibly terminating pregnancies… So… if we imagine the worse case scenario that it spread around the world, it could end reproduction of the human race. Think about that for a minute…
We now know that at last check almost 30 confirmed cases have occurred in Florida – which all of our interviewed experts predicted would happen. So the annoying little Aedes aegypti mosquito is heading north. On that terrifying note I hear the screams of: ‘oh, those evil mosquitoes. Let’s annihilate them!’ Okay, now here’s the really interesting part. It’s not really their fault. It’s pretty much our fault. Zoonotic diseases – or diseases that pass from animal to human – are becoming more and more common, and more rampant. And experts say the main reason is that we’re messing with animals and their environment way too much. So lets take a huge leap back in history for a moment and look at disease and its relationship to animals in general.
A couple of really interesting things I learned working on How the World Ends:
* disease has existed on earth LONG before humans arrived. Some say 4 billion years before us.
* all flu viruses originate in the gut of a bird
* pig’s lungs are susceptible to human viruses as well as animal viruses, so when there’s an exchange of genetic material within a pig it can be transmitted to humans
But, rather than now moving from ‘oh, those evil mosquitoes’ to adding evil little pigs and poultry to the list, let’s take a look at how we’re causing these issues.
Sonia Shah is a science journalist and author of Pandemic: Tracking Contagions from Cholera to Ebola and Beyond. We interviewed her as part of our Pandemic episode, and what she, and all our other experts are concerned about, is what they call “the jump”. That’s when an animal pathogen makes a leap to infecting humans. Six out of every ten infectious diseases in humans come from animals, and over 70 percent originate in the bodies of wild animals. And that’s where Zika came from.
So lets combine a couple of facts here. A good majority of our deadly diseases are coming from animals, and the world’s population is growing at an incredible rate. So us humans are occupying more and more animal habitats. Not only are we interacting with and living alongside wild animals, but because of our increased population we need to farm and eat more and more animals.
SARS was a pretty serious zoonotic disease that was, luckily, contained quite quickly. The severe acute respiratory syndrome originated in horseshoe bats that live in caves, moved to civet cats that live in trees, and finally to humans. Hmmmm. How could three very different species end up connecting? Take a look at wet markets in Asia. Sonia Shah visited a number of them. She saw a 30-pound turtle in a plastic bucket next to ducks, ferrets, snakes, and feral cats. She described the scene as: ‘Row after row of animals who rarely if ever encounter each other in the wild were here, breathing, urinating, defecating and eating next to each other’. This is where SARS originated.
During the 1800s human habitats spread over 90 percent of the ‘untouched, impenetrable and copepod-rich Sundarbans’. This area is in Southern Bangladesh and has the largest tidal mangrove forest in the world. As people splashed the water on their face or drank from it they invited Vibrio cholerae to jump into their bodies. This outbreak of cholera killed people faster than any known disease of the time.
Now the 1990s: during the conflict between Sierra Leone and Liberia, the SW corner of Guinea, one of the world’s most bio-diverse forests was destroyed as refugees fled the conflict and set up a new community there. Suddenly they were living among bats that had never been around humans before. Bats are well known to be great incubators of microbes that can infect humans. One of the world’s deadliest diseases, Ebola, arises – killing 90 percent of those it infects. Plus it was passed on to other animals killing one-third of the world’s gorilla population, as well as an almost equal amount of chimpanzees.
We have a few things happening: the population is moving into areas occupied by wildlife they’ve never interacted with before, and the world’s population is growing so we need more protein to feed us. So we now have pig troughs sitting near fruit trees where bats roost and their poop is dropping into the troughs. Remember what I said earlier about pig’s lungs being a great incubator for disease that can then be passed on to humans? Suddenly the domestic pig is being exposed to unusual exotic diseases, which can mutate and then become transmittable to people.
The other domestic animal, a chicken, is easy to farm. Once a chicken egg hatches it will be on your plate in 35 days. So chicken farming is increasing at an incredible rate, and so has avian flu. Currently avian flu doesn’t pass onto humans very easily, but experts say if it passes through a pig then it will be transmittable to us and could become an epidemic.
The thing with bats, birds, and mosquitoes, is they can fly. So they can spread disease as far and wide as they like. So that brings us back to that pesky little mosquito. West Nile originated in birds and was spread when mosquitoes bit the bird and then bit a human. By 2010 1.8 million people in North American had been infected with West Nile – a disease that was named after a district in Uganda where it originated in 1937. So why did it take so long to impact North America? Because the biodiversity of avian species, like that of many other species, was stronger years ago. With the spread of cities, agriculture, and even climate change we’re destroying some of the more sensitive species that don’t spread disease, and leaving what are known as the hardy ‘generalist species’ to thrive and grow stronger. These are the ones who can eat and live everywhere, as well as easily carry and spread disease.
Okay, so lots of doom and gloom. Is there hope? Sonia Shah believes there is. We need to be more sensitive to our environment and where we’re invading and expanding – changing our activities or just being aware of how disrupting certain wildlife will impact on the entire world. We need to simply not allow microbes in animal bodies to spill over into human bodies. And Sonia has incredible faith in our own immune systems: ‘we live on a microbial planet and our bodies are designed to survive that’. She’s confident that we will develop immunity to most dangerous pathogens before they can become pandemics.
So what about Zika? ‘Eighty percent of people have no symptoms at all. The other twenty percent, the vast majority of them have a rash and a fever so you may not even know you had it, but after you get through that you have immunity’.
So while we’re messing around with biodiversity, environments, animals and the world, maybe our body’s complex immune system will be able to fight back against these brand new diseases. But in the meantime, let’s not put all the blame on those pesky little mosquitoes, but take a good look in the mirror at our own actions.
Written by: Jennifer McAuley