Two years ago, few could’ve predicted that an obscure disease called Zika would be leading the news. But then the Zika-carrying mosquito spread its wings across the Western Hemisphere.
Forget lions, tigers and bears. The world’s deadliest animal is small enough to squash between your fingers. Spanish for “little fly,” the mosquito is the most lethal creature on the planet, killing more humans per year than every other animal combined.
The lowly mosquito is a wily and pernicious foe, surviving and adapting as it infects us with a rogue’s gallery of parasites and viruses, including malaria, Zika, Yellow fever, Dengue and West Nile virus. And the numbers are staggering. Each year, mosquitoes transmit disease to an estimated 700 million people — or one out of every 10 people on the planet. More than half a million of those infected will die from their encounter with mosquitoes.
Even when mosquito-borne diseases don’t kill, they cause fevers, severe pain and keep children out of school and adults out of work. Around the world, these diseases disproportionately affect the poor, destabilizing communities and driving families and communities deeper into poverty with lost pay and high health costs.
There’s no doubt that the mosquito is one of the greatest threats to our global health security. Once they’re armed with a new pathogen, they can spread disease with blinding speed.
But while mosquitoes appear like a force of nature that cannot be beaten, there is another side to the story of humanity’s battle with this tiny foe. It’s a story of stunning progress that shows what we can do when we harness human will and ingenuity to confront this age-old enemy.
It’s the story of malaria, and it begins at least 20 million years ago — some scientists say as far back as the Jurassic Period, when mosquitoes’ ancestors mingled with the dinosaurs. Malaria fevers were then described in ancient writings by the Chinese, Greeks and Romans. And, in 1897, British doctor Ronald Ross definitively proved that mosquitoes transmitted the malaria parasite.
While it’s impossible to know how many hundreds of millions of lives have been cut short by mosquitoes spreading malaria, what we do know is that 15 years ago, the disease was still killing nearly 1 million people every year — far more than all other mosquito-borne diseases combined.
Thanks to bold leadership and smart, significant investments — by the United States, the United Kingdom and other countries — we have cut that number in half in just over a decade, a feat that World Health Organization (WHO) Director General Margaret Chan calls “one of the great public health success stories” since the turn of the millennium.
Through widespread use of insecticide-treated bed nets, indoor residual spraying, better diagnostic tests and more effective treatments, we’ve slashed the rate of malaria deaths among children under five by 71% in Africa since 2000. According to WHO, 57 countries reduced new malaria cases by at least 75% between 2000 and 2015. In fact, more than 6 million people are alive today because of steadfast commitment in malaria-affected countries and ongoing financial support from the global community.
Our job is not finished — 438,000 people still die of malaria every year, mostly pregnant women and small children in Africa. But the end of this deadly disease is in sight. While the final chapter could be our most challenging, the story of malaria holds important lessons as we battle other global health scourges, particularly those carried by mosquitoes.
Innovations in data, modeling, and mapping are revolutionizing our understanding of the range of mosquitoes, and by extension, the reach of the diseases they transmit. The Malaria Atlas Project has combined reams of environmental and mosquito species data with malaria infection rates in humans to create a heat map of malaria “sources” — the places where mosquitoes naturally thrive — and “sinks,” the areas where the parasite ends up due to human travel, throughout sub-Saharan Africa.
Now we’re going further, overlaying human mobility patterns gleaned from mobile-phone usage to expose how the parasite moves within and between communities and countries, allowing us to better target our efforts to stop it.
This same approach is being applied to other mosquito species, showing how variables like temperature, rainfall and breeding habitats define the potential reach of emerging mosquito-borne diseases. Maps of the two Zika-carrying vectors (Aedes aegypti and Aedes albopictus) showed a potential spread from southernmost Brazil to the US-Canada border, an area in which over 5.4 million births occurred in 2015 — of particular concern because of the devastating effects of Zika exposure during pregnancy.
And while the stories of malaria and now Zika remind us how much we already know about beating mosquitoes, they also serve as stark reminders of the dangers of losing focus.
We have seen more than 75 instances of malaria resurgence around the world in the past century, most linked to decreases in funding. Worse yet, malaria flourishes when routine health services are disrupted. When the Ebola crisis broke out in West Africa in 2014, estimates in The Lancet suggested that malaria could claim as many lives as Ebola did in affected countries. More recently, the economic collapse in Venezuela has brought malaria roaring back.
Mosquitoes and the diseases they carry continue to build resistance to the tools we have to fight them. Drug-resistant malaria in Southeast Asia is an urgent concern, as it threatens to spread to other parts of the world and rob us of our frontline treatment.
As we face ever-adapting mosquitoes, we need to sustain our focus on the fundamentals of mosquito control. We need to continue our quest for an effective vaccine, and we need to realize the full potential of big data to target our approaches — to detecting, tracking and treating malaria. We also need novel insecticides and other ways to keep mosquitoes from infecting us in the first place.
In one promising approach, scientists are exploring how a new gene-editing technology called “gene drive” could be used to produce mosquitoes incapable of reproducing or transmitting disease. As with any new technology, there are valid questions about safety, ethics and environmental impact that need to be addressed thoughtfully and with broad participation from affected countries. But there are too many lives at stake to avoid these kinds of hard questions.
Now, more than ever, it’s crucial to sustain our commitment to ending malaria and expand scientific research to keep the world safe from our tiniest, deadliest foe.
