I’ve been perpetuating a misconception.
When I give talks about global health, I typically speak about microbes as threats we need to wipe off the map. And it’s certainly true that some microbes, like the ones that cause malaria and tuberculosis, are responsible for tremendous suffering and death around the world. But the view that microbes always equal disease and are essentially bad things is an oversimplification.
I’m seeing microbes with new eyes and talking about them in different terms thanks to British journalist Ed Yong. After reading his super-interesting book I Contain Multitudes, I had a chance to chat with him in person about his view that “microbes are mostly not to be feared or destroyed but to be cherished, admired, and studied.”
In I Contain Multitudes, Yong synthesizes literally hundreds and hundreds of papers, but he never overwhelms you with the science. He just keeps imparting one surprising, fascinating insight after the next. I Contain Multitudes is science journalism at its best.
Yong makes clear that only a tiny fraction of microbes have the ability to make us sick. There are approximately 100 species of bacteria that cause infectious disease in humans. But there are hundreds of thousands of species that live peacefully, symbiotically within us, primarily in our gut. Microbes help us digest our food, break down toxins, guide our physical development, protect us from disease, and even speed human evolution. We are utterly dependent on them.
We are also utterly inseparable from them. Yong illustrates that we are at least as much microbe as human. We literally have more microbial cells living inside our bodies than human cells. And even the cells we label “human” are part microbe. With the exception of red blood cells and sperm, all our cells are powered by mitochondria, which are likely the descendants of ancient bacteria that became integrated into the type of cells that subsequently gave rise to all complex life. (The story of how that happened is the subject of another book I loved: The Vital Question, by the biologist Nick Lane.)
I found some of Yong’s reporting directly relevant to my role as a parent. Melinda and I—and most parents in the U.S. and other rich countries—have dramatically cut down on our children’s exposure to the diverse array of microbes that for millennia have helped human beings strengthen their immune systems and avoid inflammatory diseases. As Yong puts it, “We have been tilting at microbes for too long, and created a world that is hostile to the ones we need.”
It’s not just all the anti-bacterial soaps and sanitizers we Americans use. Another major problem is the excessive use of antibiotics. On net, antibiotics have been unbelievably positive for humanity. But every time we give them, we are carpet-bombing our microbial ecosystem (microbiome), not merely knocking out pathogens. “A rich, thriving microbiome acts as a barrier to invasive pathogens,” writes Yong. “When our old friends vanish, that barrier disappears [and] more dangerous species can exploit the … ecological vacancies.”
As you can imagine, the book is also quite relevant to my work at our foundation, especially in the area of children’s growth and development. Yong explains why, if we want to prevent malnutrition, we not only need to help alleviate hunger and provide key micronutrients. We will also need to learn why some kids’ microbiomes are out of balance and how to restore them back to a healthy state.
Not only could this lead to low-cost interventions for malnutrition. I suspect this line of research will also help scientists make inroads against many other diseases. The list of disorders that have been linked to disruptions in the microbiome includes Crohn’s disease, ulcerative colitis, irritable bowel syndrome, colon cancer, obesity, type 1 diabetes, type 2 diabetes, and Parkinson’s disease. Even though we don’t have good ways of manipulating the microbiome to head off disease, I am hopeful we will eventually. I’m particularly excited about the implications for neurodegenerative diseases like Parkinson’s. It may turn out that these diseases get their start in the gut a decade or more before any brain symptoms show up. If that’s the case, the gut may prove to be a great target for medicines, giving new hope to many millions of families.
Another area of intense interest for Yong and for me is harnessing benign microbes to fight dangerous ones. Our foundation has been supporting some cutting-edge work to infect certain species of mosquitoes with a very common bacterium called Wolbachia to make it impossible for these mosquitoes to spread a painful, debilitating disease called dengue fever.
As Yong reports, this approach worked wonders in its first field trial, in eastern Australia. In just four months, Wolbachia-infected mosquitoes almost totally replaced the mosquitoes capable of carrying the virus that causes dengue—effectively wiping out dengue in the region. (I had a chance to see and report on this work on a visit to Indonesia in 2014.) The implications of these tests are huge. We believe that Wolbachia could also be effective at stopping the spread of other viruses, such as Chikungunya and Zika. This approach might also have the potential to be a powerful tool in the fight against malaria.
In the end, I Contain Multitudes is a healthy corrective. Yong succeeds in his intention to give us a “grander view of life” and does so without falling prey to grand, unifying explanations that are far too simplistic. He presents our inner ecosystems in all their wondrous messiness and complexity. And he offers realistic optimism that our growing knowledge of the human microbiome will lead to great new opportunities for enhancing our health.