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Is the pandemic over? No, not even close, but it’s understandable why many people think it might be. States are reopening, and people’s behaviors are changing. Masks are coming off. Friends are socializing. Groups are congregating. COVID-19 is still prevalent in many communities, but because we can’t see it, we focus on behavior instead: what others are doing and what we think we should be doing. But behavior can easily become disconnected from the contagion it is meant to avoid.
Consider a trip to the local supermarket. We can still shop at supermarkets because COVID-19 is not reliably transmitted by contact with surfaces, including food packaging, but many supermarkets have banned shoppers from bringing reusable bags, which are just another surface. Supermarket employees assiduously wipe down carts between uses, but no one wipes down the credit card machines between transactions. And shoppers wear masks as they pass one another, but they adjust their masks with their hands or pull them down to talk to the cashier.
Our behavior in the face of contagion can be erratic because we have no way of perceiving the contagion itself and must rely on other cues. One such cue is disgust. Humans are universally disgusted by contagion-laden substances like rotting food and bodily waste. But there are many things devoid of contagion that disgust us, and many contagions that fail to elicit disgust. Diseases like cholera and smallpox spread because humans are not inherently disgusted by cholera-infected water or smallpox-infested blankets, and clean substances that resemble contagion-laden ones, like sterile bedpans or feces-shaped fudge, regularly elicit a disgust response. Disgust, by itself, is an unreliable guide.
Knowledge about germs is a much better guide. But just knowing that germs exist is not sufficient. We must actively consider where germs reside, where they thrive, how they spread, how they enter the body, and how they can be killed. Germs are living things adapted to survive and reproduce inside other living things, and we must think of them as such in order to curtail their spread.
Germs were discovered in the 17th century with the advent of the microscope, but were not linked to disease for another 180 years, given how counterintuitive it is to think that other organisms live and breed inside us. Today, we learn of germs early in life, through admonishments to avoid them and wash them from their bodies, but we do not naturally view them as alive. From early childhood, we know that rotting food has germs, that sick people have germs, that germs can be passed from contaminated objects to uncontaminated ones, and that the process of contamination is undetectable, yet we still think of germs more as toxins than microbes. We balk at the suggestion that germs engage in biological processes, like metabolism and respiration, and we are prone to conflate diseases caused by germs with diseases caused by inorganic substances, like poison or pollution.
Teaching people to think of germs as living things has profound consequences for health behavior, as demonstrated by the psychologist Terry Kit-fong Au. In one study, Au and her colleagues developed a health education program that taught the causal principles behind cold and flu prevention, dubbed Think Biology. Conventional health education programs focus on behavior: the do’s and don’ts of disease prevention. Think Biology, in contrast, focused on knowledge: the why’s and how’s of disease prevention. Its main objective was to get students to conceptualize germs as living, reproducing organisms rather than as inert substances like poison. It emphasized (1) that viruses are tiny living things too small to see with the naked eye; (2) that cold and flu viruses can survive for several hours in cool, humid air but are quickly killed by heat and disinfectants, (3) that only live strains of virus can cause colds and flu, and (4) that cold and flu viruses enter the body through the eyes, nose, and mouth.
Au administered the Think Biology program to a group of third-graders in Hong Kong. She compared their progress with third-graders who received a more conventional health education program. The conventional program did not cover any of the biological underpinnings of cold and flu infection but instead covered cold and flu symptoms, treatments, preventative behaviors (do’s), and risk factors (don’ts).
Children in both health education programs learned to explain illness in terms of germ transfer, but only children in the Think Biology program could explain why germ transfer was harmful (because germs, once transferred, replicate inside their hosts). Children in both programs also learned the various risk factors taught during instruction, but only children in the Think Biology program could identify novel, untaught risk factors. Most significantly, only children in the Think Biology program changed their disease-prevention behaviors when observed covertly. The children were asked to help the experimenter package food, and they were observed for whether they first cleansed their hands with hand sanitizer. Children in the conventional program rarely did so, either before instruction or after. Children in the Think Biology program, on the other hand, increased their hand cleansing by nearly a factor of three.
Au and her colleagues achieved similar success with a program designed to teach adolescents about the biological underpinnings of sexually transmitted diseases. The power of such programs comes from teaching ideas that are not just more accurate but also more flexible. No health education program could cover all behaviors associated with the spread of a particular disease, and no student could memorize that list. An effective program provides students with the conceptual tools to evaluate risk in the moment, as new disease-relevant situations unfold.
As a case in point, Au and her colleagues observed a curious breakdown in disease-prevention behavior in the Hong Kong schools where they tested their Think Biology program. Children in this school washed their hands dutifully before lunch, only to recontaminate them minutes later by touching the face masks they wore as a precaution against the 2003 outbreak of severe acute respiratory syndrome (SARS). These face masks were the most contaminated objects in the children’s environment, as they were covered in microbes filtered from the children’s airstream throughout the day. “Don’t touch your face masks” was not a rule covered in either health prevention program, but it was a rule that could be inferred from the principles conveyed by the Think Biology program. In fact, many children did infer this rule, labeling the touching of face masks as a risk factor for disease transmission following instruction.
Masks have once again become a necessity for promoting public health, but casual observation of how people use (and misuse) their masks suggests that the behavioral prescription to wear a mask is not accompanied by thoughtful consideration of why masks are important or how they curtail the spread of airborne disease. Identifying the do’s and don’ts of disease prevention is an important first step, but those prescriptions need to be adopted mindfully, with consideration of the biological reality of what microbes are and how they spread.
