COVID-19 hijacked people’s lives, families and work. And hijacked their bodies and minds in ways that they may not even be aware of.
In our view, SARS-CoV-2, the virus that causes COVID-19, is a kind of zombie virus, transforming people not into the undead, but into the non-sick. By interfering with our body’s normal immune response and blocking pain, the virus keeps infected people on their feet, spreading the virus.
People often think of zombies as a science fiction thing. But in the biological world, zombies are everywhere, from the fungus Ophiocordyceps that is perpetuated by zombie ants; to Toxoplasma gondii, a single-celled parasite that completes its life cycle by taking rodents to the predatory jaws. Zombie viruses are also real, influencing their host’s behavior in ways that increase the virus’s evolutionary fitness.
One of us is a professor of psychology. The other is an emergency doctor. We are both researchers in evolutionary medicine. And we suggest to you that SARS-CoV-2, the virus that causes COVID-19, is more of a zombie virus, a master manipulator operating under the radar. This pandemic may have triggered a horde of non-sick people: infected and unconscious victims of a manipulative virus.
Radoslav Zilinsky via Getty Images
How the virus makes us sick
It is the non-sick who spreads the virus most readily. About 40% of people with SARS-CoV-2 are asymptomatic disseminators, never showing any symptoms. And those who show symptoms are more contagious in the two days before the symptoms appear. Why people don’t feel bad before – or even bad – may be part of the SARS-CoV-2 evolutionary strategy.
A look under the hood of the virus reveals more about this manipulative machine. SARS-CoV-2 interferes with a person’s immune response; that’s why people don’t necessarily feel sick and withdrawn as they would a typical viral infection. Instead, SARS-CoV-2 silences the body’s alarm signals that would otherwise orchestrate antiviral defenses. It blocks interferons, a set of molecules that help fight viruses. Interferon activity makes people feel more depressed and socially withdrawn – so when the new coronanvirus prevents interferon activity, your mood improves, sociability increases and you feel less sick.
The virus also decreases the perception of pain. Usually, pain motivates us to calm down when we need to heal. But SARS-CoV-2 blocks that response, preventing the transmission of pain signals. That is why people feel good even when they are full of viruses before symptoms start.
At the same time, SARS-CoV-2 attenuates the body’s response to infection. It prevents pro-inflammatory cytokines, molecules that help stimulate the immune response. It also makes the hosts feel better than they should. Normally, feeling sick helps our body to prioritize healing, making us reduce our energy expenditure. With SARS-CoV-2, non-sick hosts have the energy to do as much as before, perhaps more.
An evolutionary leg up
How SARS-CoV-2 evolved to manipulate humans is still speculation. The virus may have evolved first in other mammals, such as pangolins. There, he may have acquired his immune avoidance manipulating machine before jumping on humans.
No intention or thought is involved; SARS-CoV-2 is not planning to take control of your body. This is simply evolution at work, nothing personal. The virus evolves due to variation and selection. And in a pandemic involving hundreds of millions of infections and trillions of viral replications, many genetic variants could give you an evolutionary advantage.
More research is needed to determine whether the new variants make people feel ill any longer. This, of course, would make it even easier for the virus to spread during the asymptomatic phase. For example, an article in the Journal of Transnational Medicine reported that the GZ69 variant is associated with high elimination rates in asymptomatic patients, which means that people are highly contagious even when they are feeling well.
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It is possible that SARS-CoV-2 makes people feel even better than they would without the virus infection. One study found that people did not reduce their time in public even when they had symptoms of COVID-19. In fact, they came out more. Any variant that does this clearly has an evolutionary advantage when it comes to transmission. Using surveys and social media data, our research team is now testing whether people are more social during their most contagious days.
Things to consider
We must take seriously the possibility that the virus is buzzing us – changing our behavior in ways that help to perpetuate it. By making people feel good when they are able to spread the virus, SARS-CoV-2 spreads under the radar, more like a sexually transmitted disease than a respiratory virus.
Many of us have inadvertently acted as vehicles for its spread, with impressive implications. Our behavior may not serve our own evolutionary interests. Instead, the non-sick person may be transmitting the virus.
Researchers often ignore the impact that viruses can have on our mood and behavior. But, like ants and rodents, humans are not exempt from the neural and behavioral sequestration that is widespread in the natural world.
We believe that it is essential to consider the possible “anti-symptoms” of this virus: temporary pain reduction, feeling more energetic than normal and maybe even wanting to be closer to people than normal. With all that in mind, here’s a piece of advice, probably the most ironic that you heard last year: If you’ve been feeling surprisingly good in the past few days, you might want to take a COVID-19 test.