1:Children Are Microbe Magnets
Microbes: Kill Them All!
Microbes are the smallest forms of life on Earth. They encompass bacteria, viruses, protozoa, and other types of organisms that can be seen only with a microscope. Microbes are also the oldest and most successful forms of life on our planet, having evolved long before plants and animals (plants and animals actually evolved from bacteria). Although invisible to the naked eye, they play a major role in life on Earth. There are an astounding 5 x 1030 (that’s 5 followed by 30 zeroes!) bacteria on Earth (for comparison, there are “only” 7 x 1021 stars in the universe). Collectively, these microbes weigh more than all the plants and animals on the entire planet combined. They can live in the harshest and most inhospitable environments, from the Dry Valleys of Antarctica to the boiling hydrothermal vents on the seafloor—they can even thrive in radioactive waste. Every form of life on Earth is covered in microbes in a complex yet usually harmonious relationship, making germophobia the most futile of phobias. Unless you live in a sterile bubble without any contact with the outside world (which is a time-limited proposition; see Bubble Boy, page 15), there is no escaping microbial life—we live in a world coated in a veneer of microbes. For every single human cell in our bodies, there are ten bacterial cells inhabiting us; for every gene in our cells, there are one-hundred fifty bacterial genes, begging the question: Do they inhabit us or is it really the other way around?
While in its mother’s womb a baby is for the most part sterile, but at the moment of birth it receives a big load of microbes, mainly from its mother—a precious first birthday gift! Within seconds, the baby is covered in microbes from the very first surfaces it touches. Babies born vaginally encounter vaginal and fecal microbes, whereas babies born via C-section pick up microbes from the maternal skin instead. Similarly, babies born at home are exposed to very different microbes than if they are born in hospitals, and different homes (and hospitals) have different microbes present.
Why does all this matter? Well, until very recently hardly anyone thought it did. Until recently, whenever we thought of microbes—especially around babies—we considered them only as potential threats and were concerned with getting rid of them, and it’s no surprise why. In the past century, we have experienced the benefits of medical advances that have reduced the number and the degree of infections we suffer throughout life. These advances include antibiotics, antivirals, vaccinations, chlorinated water, pasteurization, sterilization, pathogen-free food, and even good old-fashioned handwashing. The quest of the past hundred years has been to get rid of microbes—the saying was “the only good microbe is a dead one.”
This strategy served us remarkably well; nowadays, dying from a microbial infection is a very rare event in developed countries, whereas only a hundred years ago, seventy-five million people died worldwide over a span of two years from the H1N1 influenza virus, also known as the Spanish flu. We have become so efficient at avoiding infections that the appearance of a dangerous strain of Escherichia coli (aka E. coli) in a beef shipment or Listeria monocytogenes in spinach leads to massive recalls and exportation bans, along with accompanying media hysteria. Microbes scare all of us, and rightly so since some of them are truly dangerous. As a result, with very few controlled exceptions such as yogurt or beer, we often think that the presence of microbes in something renders it undesirable for human use. The word antimicrobial is a sales feature in soaps, skin lotions, cleaning supplies, food preservatives, plastics, and even fabrics. However, only about one hundred species of microbes are known to actually cause diseases in humans; the vast majority of the thousands of species that inhabit us do not cause any problems, and, in fact, seem to come with serious benefits.
At first glance, our war on microbes, along with other medical advances, has truly paid off. In 1915 the average life span in the US was fifty-two years, about thirty years shorter than it is today. For better or for worse, there are almost four times more humans on this planet than there were just a hundred years ago, which translates to an incredibly accelerated growth in our historic timeline. Evolutionarily speaking, we’ve hit the jackpot. But at what price?
Revenge of the Microbes
The prevalence of infectious diseases declined sharply after the emergence of antibiotics, vaccines, and sterilization techniques. However, there has been an explosion in the prevalence of chronic non-infectious diseases and disorders in developed countries. One hears about these in the news all the time since they’re very common in industrialized nations, where alterations to our immune system play an important role in their development. They include diabetes, allergies, asthma, inflammatory bowel diseases (IBDs), autoimmune diseases, autism, certain types of cancer, and even obesity. The incidence of some of these disorders is doubling every ten years, and they are starting to appear sooner in life, often in childhood. They are our new epidemics, our modern-day bubonic plague. (By contrast, these diseases have remained at much lower levels in developing countries, where infectious diseases and early childhood mortality are still the major problems.) Most of us know someone suffering from at least one of these chronic illnesses; due to this prevalence, researchers have focused their attention on identifying the factors that cause them. What we know now is that although all of these diseases have a genetic component to them, their increased pervasiveness cannot be explained by genetics alone. Our genes simply have not changed that much in just two generations—but our environment sure has.
About twenty-five years ago a short scientific article published by an epidemiologist from London attracted a lot of attention. Dr. David Strachan proposed that a lack of exposure to bacteria and parasites, specifically during childhood, may be the cause of the rapid increase in allergy cases, since it prevents proper development of the immune system. This concept was later termed the “hygiene hypothesis,” and an increasing number of studies have explored whether the development of many diseases, not just allergies, can be explained by this hypothesis. There is now a large amount of very solid evidence, which we’ll examine in the following chapters, supporting Dr. Strachan’s proposal as generally correct. What remains less clear is what exact factors are responsible for this lack of microbial exposure. For his study on allergies, Dr. Strachan concluded that “declining family size, improvements in household amenities, and higher standards of personal cleanliness” contributed to this reduced contact with microbes. While this may be true, there are many other modern-life changes that have an even stronger impact on our exposure to microbes.
One of these changes can be attributed to the use, overuse, and abuse of antibiotics—chemicals that are designed to indiscriminately kill bacterial microbes. Definitely one of, if not the greatest discovery of the twentieth century, the emergence of antibiotics marked a watershed before-and-after moment in modern medicine. Prior to the advent of antibiotics, 90 percent of children would die if they contracted bacterial meningitis; now most cases fully recover, if treated early. Back then, a simple ear infection could spread to the brain, causing extensive damage or even death, and most modern surgeries would not even be possible to contemplate. The use of antibiotics, however, has become far too commonplace. Between the years 2000 and 2010 alone there was a 36 percent increase in the use of antibiotics worldwide, a phenomenon that appears to follow the economic growth trajectory in countries such as Russia, Brazil, India, and China. One troubling thing about these numbers is that the use of antibiotics peaks during influenza virus infections, even though they are not effective against viral infections (they are designed to kill bacteria, not viruses).
Antibiotics are also widely used as growth supplements in agriculture. Giving cattle, pigs, and other livestock low doses of antibiotics causes significant weight gain in the animals and, subsequently, an increase in the meat yield per animal. This practice is now banned in Europe, but is still legal in North America. It seems that antibiotic overuse in humans, especially in children, is inadvertently mimicking what occurs in farm animals: increased weight gain. A recent study of 65,000 children in the US showed that more than 70 percent of them had received antibiotics by age two, and that those children averaged eleven courses of antibiotics by age five. Disturbingly, children who received four or more courses of antibiotics in their first two years were at a 10 percent higher risk of becoming obese. In a separate study, epidemiologists from the Centers for Disease