Too Clean for Our Own Good: COVID and the Hygiene Hypothesis
It's been nearly two years since we entered an alternate reality of the Covid-19 pandemic, where masks, sanitizers, and overwhelming feelings of isolation have become commonplace. Society has largely adjusted to the new way of life; we have become Zoom experts, mastered the art of business professional from the waist up, and can find a spare mask in every jacket pocket.
Nevertheless, the pandemic has undoubtedly had unimaginable effects on individuals' lives and the world at large, and as we spend more time living in our science-fiction reality, the long-term ramifications of this new way of life will only become more apparent. In the wake of this health crisis, many questions arise about how the pandemic will affect the health of humanity. On a personal level, relating to the immune soldiers who are ultimately at the front line Covid infection, how has the pandemic and the lifestyle it fostered impacted our immune systems?
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Does social distancing weaken the immune system?
Many fear that because social distancing reduces our exposure to pathogens, putting our immune systems out of practice, some suggesting it may weaken our bodies natural line of defense.
However, this is not how the immune system works. A cascade of pathways is triggered when your body encounters a foreign pathogen, resulting in a battle between microbes and thousands of immune cells. Among these is the B-cell, responsible for producing antibodies, which work by perfectly fitting to a receptor on the invader like a lock and key. This link incapacitates the pathogen and enables you to win the fight against most diseases you come into contact with. However, it takes time to produce the perfect antibody, and so you fall ill during this period, while your body trains its best sharpshooters to join the immunological battle.
Once you recover, the B-cell producing that specific antibody stays around, becoming a memory cell. This way, if you ever come into contact with the same pathogen, the antibodies will be produced right away and the battle quickly won, preventing you from get physically ill. This gained immunity will not go away by lack of exposure to pathogens, as most adults have a robust, functioning immune system with immunity built up from years of life experience and exposure to all kinds of diseases. As we slowly return to socialization, a new strain of flu is sure to make its rounds, but mild illness is nothing a healthy immune system cannot handle.
While social distancing will not affect a developed immune system, the developing immune systems of children require exposure to disease to build immunity and function properly. Immune system development, building a catalog of T and B cells that will eventually provide immunity to a whole host of diseases, is a process that occurs rapidly in childhood and is largely finished by age 8. The first 100 days of life appear to be a critical period for immune development, and exposure to less microbial diversity in this window is associated with higher rates of asthma, allergies, and type one diabetes later in life. Based on these findings, it is entirely possible that children born during the pandemic, into a sterile world, may have higher rates of autoimmune disorders than their pre-pandemic brethren. However, only time will tell, and rates of these diseases have been rapidly increasing since the 1960s. This phenomenon is best explained by the hygiene hypothesis: the idea that being so clean is what’s making us sick.
The Hygiene Hypothesis
If you have older siblings, you are less likely to have allergic disorders than only children. This notion served as the basis for the hygiene hypothesis, thinking that an infant's exposure to their non-sterile older sibling(s) is what gives them a healthy immune system. This line of thought, that reduced exposure to germs increases allergies, has been extended to say that the overall conditions of first world countries in the 21st century, with potable water, easy sanitation, and readily available antibiotics, have lead to an overactive immune system because it is not being utilized nearly as much as it was evolutionarily.
For most of human history, worms posed a huge threat to survival, so much so, we have a specialized class of antibodies whose sole function is to mitigate parasitic infections. However, in modern, industrialized society with clean water, worms have become less common, and so these antibodies never get to fulfill their evolutionary purpose. Confused and without a job to do, these antibodies target non-pathogenic molecules, sometimes mistakenly recognizing a harmless peanut for an immunological threat. Because allergic reactions are caused by the same class of antibodies as parasitic infections, this phenomenon, along with reduced childhood exposure to pathogens, may explain the rise in allergies in modern times, and could even account for even higher rates of disease in a post-pandemic world.
A child raised in a society where everyone around them is wearing masks will not be exposed to nearly as many germs as a child born before the pandemic. While masks may keep them from getting sick in the short term, experts worry that reduced exposure to microbes leaves them vulnerable to worse infections in the future. Last May in the UK, doctors saw uncharacteristically high rates of respiratory syncytial virus (RSV) as mask mandates were lifted and children faced the pathogen-laced world for the first time.
This statistic is concerning, as it indicates that as we attempt to stop the spread of one virus, we may be making children’s immune systems weaker to infections from others. Longer term effects of this stunted immune development will only be revealed in the coming years. Allergies and other autoimmune disorders are incredibly detrimental, and may be easier to prevent through proper immune exposure than treatment later in life. If we want to stay healthy, we cannot be too clean. Our children must play in the mud, and they must get sick.
Helping your immune system out
While we do not have control over how our immune systems develop or what they may react to, we can still support their best functioning, and still in the midst of a pandemic, it is crucial we do this. The immune system is incredibly complex and responds to a multitude of factors, many of which are not well understood. We do know that while social distancing does not inherently weaken the immune system, feelings of loneliness or isolation are associated with an increased risk of mortality as well as infectious and cardiovascular diseases. Our psychological state has huge impacts on our physiological state, and stress has a very negative impact on the immune system. Receiving adequate sleep and nutrients will do the body wonders in keeping you healthy. Vitamins C and D are especially important in immune functioning, as they aid in cellular communication; low levels of vitamin D have even been linked with increased mortality from COVID-19. While the body's immune system is complex, small actions can improve immunological health. Even taking a moment to stand in the sun or drink a glass of orange juice may help the system fighting to keep you healthy at every moment of your life.