The next day, Teresa set out to see her old friend, Professor Richard, hoping he could help with Mark’s treatment. After a long journey, she finally reached her friend’s clinic at the university—only to learn that Richard was in the middle of a lecture. Knowing how productive and engaging his classes always were, she found the lecture hall, slipped quietly through the door, and took a seat in the back row. She was relieved to see that he had just opened a new slide; she hadn’t missed anything.

“Today,” Professor Richard began, “we will discuss the role of bacteria and viruses in human life and briefly examine some of the great pandemics throughout history.”
He paused, letting the statement settle, then asked a question meant to stir his students awake:
“Who can tell me how many bacteria you are carrying in your body right now?”

A mischievous student, reminded of an old joke, replied,
“Sir, we each have as many bacteria as the number of hairs on your head.”

Professor Richard smiled knowingly.
“I know exactly which joke you’re thinking of. A wise man, tired of being asked pointless questions about how many hairs or strands of fur he had, once replied: ‘I have as many as the hairs on my donkey.’ When the man stared in disbelief, he simply said, ‘Count them, if you don’t believe me.’
We cannot know the exact number of bacteria living on us—but we also cannot dismiss that number as meaningless. This vast world, sometimes a loyal ally and sometimes a lethal enemy, demands that we understand its sheer scale and diversity. Only then can we prepare effective defenses, whether against individual illness or widespread pandemic.”

A bespectacled student, worn down by reading, raised his hand hesitantly.
“According to the news, a new outbreak has started in China. Experts are predicting global deaths in the near future. They say there is already someone in our country showing symptoms—and that he’s been secretly quarantined.”

Richard nodded. “All right, we’ll get to that,” he said, before continuing.

“When you go to a zoo, the predators capable of harming you—lions, tigers, certain venomous snakes and scorpions—are kept under strict precautions. Their enclosures are specially designed, reinforced, controlled. We cannot simply lump them all together as ‘animals’ in the same sense.
Likewise, not all dogs are the same. A breed that looks tame—like a Doberman—can, for reasons we don’t understand, suddenly attack and bite someone. Even an elephant, normally gentle, can lose its temper and trample a person. The world of bacteria and viruses functions very much like that.”

“So what you’re saying is that there are beneficial, neutral, and harmful species of single-celled organisms—or that some, though harmless at first, can become dangerous later on. We already know bacteria convert atmospheric nitrogen into ammonia, making it usable for us. We know the ones in our gut help digestion and produce B2, B12, and folate. And of course, we know harmful bacteria and viruses are responsible for infectious diseases. What exactly are you trying to emphasize beyond these?” another student asked.

“Yes, those are correct statements—what you learned before university,” Richard replied. “But let’s look at the numbers. It’s estimated that there may be around a million bacterial species. As for their total population on Earth—our numbers simply aren’t big enough to quantify it.”

“There are about thirty to forty trillion cells in a human body. Researchers believe we carry at least that many bacteria—possibly many times more. Out of this vast microbial world, roughly 1,500 species are capable of causing disease in humans.”

“And then there are viruses: hundreds of thousands of types. From rhinoviruses that merely cause the common cold to HIV, which is profoundly lethal. We know of around five hundred pathogenic viruses with wildly different traits. Some aren’t lethal but still disruptive—herpes viruses, for example, which can ruin a person’s quality of life.”

“When you look at these numbers,” Richard continued, “you begin to see that single-celled organisms, in both diversity and quantity, greatly surpass all existing and extinct animal species combined. And specialists say that if you gathered every microorganism on Earth—though they are invisible to the naked eye—their total mass would outweigh all animals by several orders of magnitude.”

He smiled faintly as he let that fact settle over the room.

“I only hope that humans and microbes never go to war,” Richard said. “If such a conflict ever began, the enemy would outmatch us in everything: in numbers, in diversity, in mass, even in the biochemical weapons they release. Hidden or cryptic enemies are already the greatest fear in military strategy. And in such a war, our nuclear arsenal and our high-tech laser robots would be utterly useless.”

“We’d drown them in oceans of disinfectant,” one student joked.

“There are bacteria and viruses that are immune to disinfectants,” Richard replied, unmoved. “And, as I mentioned earlier, many of these tiny beings are vital to our survival. Without them we would die. The ideal solution would be to catalog every microbial species—millions of them—and determine which are allies and which are enemies. But that’s impossible in practice. Modern science focuses mostly on pathogens already identified, on viruses we encounter frequently, like herpes or rhinovirus, and on common bacterial groups such as streptococci and staphylococci.”

He paused a moment before continuing. “And even within a single family of microbes, variation is enormous. Just three or four years ago, researchers in England discovered more than a hundred previously unknown gut-bacteria species. With viruses, our ignorance is even deeper. They’re far smaller than bacteria—so small that only the most advanced microscopes can visualize them.”

Sitting quietly in the back row, Teresa listened with growing interest. She couldn’t help thinking, You should at least mention COVID, considering how recent and relevant it is.
Richard, as if reading her mind, adjusted his glasses and continued.

“I’m not giving you these numbers merely to say that we know only one-thousandth of this enormous microbial world. I’m telling you that the remaining 999 parts out of a thousand will remain invisible unless a specific research project or a disease outbreak forces us to isolate them. For centuries, epidemics swept through populations. Without microscopes, people identified diseases not by the nature of the pathogen, but by symptoms. That means many past epidemics may have been caused by microbes we’ve never truly observed. It also means that something like the coronavirus might have been with us all along—quiet, dormant—until some unknown trigger switched it on.”

“So you’re claiming COVID didn’t arise by natural or engineered mutation?” a student asked.

“I’m not claiming that,” Richard said. “Mutation is unquestionable in viruses. But we cannot ignore the chilling theory inspired by researcher Sonea’s discovery.”

The eagerness in the students’ eyes suddenly dissolved into unease. Headlines about the coronavirus ending humanity seemed to flash before them all at once.

“The researcher I mentioned argues that for unicellular organisms to develop enzymes resistant to antibiotics and antivirals through random mutation alone, they would need roughly a million years,” Richard said. “Inspired by this statement, some scientists propose something far more unsettling: that bacteria and viruses can communicate among themselves, exchanging information that accelerates their resistance in a dramatically shorter time.

In this way, they might attack their enemies—us—with far more sophisticated biochemical weapons. They compare this to the body’s own cells. As you know, there are over two hundred different cell types in the human body. They differ in form, function, and purpose, yet they work in harmony through invisible connections. Without that harmony, we would die.”

“Some researchers claim bacteria and viruses function like the cells of two separate bodies,” He continued. “To support their theory, they point to this: symptoms of an outbreak emerge in distant places on the same day, hundreds of miles apart, in populations with no aviation, train, or transport links between them. The same disease appears simultaneously in multiple, isolated locations. The only explanation, they argue, is that viruses and bacteria are signaling across distance—telling their counterparts, ‘We are now producing enzymes that make us pathogenic to humans,’ and urging them to activate the same traits.”

A pale-faced young woman raised her hand, though her voice trembled. “You’re saying they might actually… talk? As in, transmit messages to one another?”

Richard exhaled, slow and cautious. “I can’t say for certain. But it is a theory we should not dismiss lightly.”

“Of the known viruses, 586 are pathogenic only to animals, while roughly half that number are capable of causing disease in humans. But there is no guarantee that those currently confined to animals will not someday cross the species barrier. So, young lady—if I were you, I would think twice before eating chicken or beef, or at least make sure I only eat from places where the meat is reliably cooked at sufficiently high temperatures.”

The students immediately recognized Professor Richard’s reference to mad cow disease and avian influenza—illnesses that had leapt from animals to humans with catastrophic consequences.

“Isn’t it strange,” he continued, “that some bacteria, whose average lifespan is barely twenty minutes, and viruses—organisms whose very status as ‘alive’ has been debated for decades, and which cannot survive without a host—possess reproductive, defensive, and communicative abilities far more sophisticated than our own? Human beings only discovered electromagnetic communication in the nineteenth century, yet these microscopic creatures have been using comparable signaling mechanisms for millions of years.”

A student, eyebrows raised, stared at him with a troubled expression.
“I’m confused. Are they superior to us, or are we superior to them? Did humanity evolve from something as simple as a microbe, or are we devolving back toward it?”

The professor smiled faintly.
“That is a question you should ask those who try to force every scientific discovery—every behavior, every impulse, even human proclivity toward violence—into the framework of microbial evolution. If you ask me, every form of life was created with its own distinct potential and purpose.”

Teresa found herself agreeing with the professor. She recalled a book she had recently read: its protagonist flirted with multiple women at once, cheated on his wife, and did not hesitate to use violence when it suited him. Near the end of the novel, the author revealed that the man’s destructive behavior stemmed from what he had witnessed in his childhood—his father mistreating his mother and other women—traumas etched so deeply into his subconscious that they shaped his adult impulses.

That explanation, Teresa admitted, was consistent with established psychological and medical understanding: experiences in childhood can indeed become trauma and later manifest as maladaptive tendencies.

What bothered her, however, was the author’s attempt to use that trauma as evidence that humanity had evolved from microbes. Even stranger was the fact that the first editions of the book had contained no such reference to evolution, while later editions had inserted it, almost artificially.

Professor Richard’s voice brought her back to the amphitheater with a promise of optimism.
“I also have good news. In nature, there is always a balance. A strong predator may easily hunt the weak, but it always has an enemy. The lion is checked by the tiger, the wolf by the dog. This prevents any one species from gaining absolute dominance, and through this struggle, weaker species survive and continue their lineage.

This law also exists among humans. If the West possessed unchecked superpower status without a counterbalance in the East—or perhaps the North—what would become of the world? Or imagine a nation where only one political faction existed, with no opposing ideology—what kind of tyranny would emerge?

My point is not to criticize any particular nation, belief, or ideology. Regardless of identity, absolute power inevitably leads to intoxication and injustice. Whether in humans, animals, or microorganisms—this truth does not change.”

He advanced to the next slide.
“Now, back to our topic. As you can see from these images of bacteria and viruses glaring at one another, they are ancient, relentless enemies. They despise each other. No bacterium welcomes an uninvited viral parasite into its body.

Yet they are among the most populous biological entities on the planet. Many viruses, though not all, possess what we call a phage—a weapon. A specific virus targets a specific bacterium. And theoretically, that weapon could be used to counter an outbreak caused by pathogenic bacteria—if the correct virus were deployed against its natural enemy.

So far, we have rarely, if ever, needed to resort to that… or at least, that is what we believe.”

“What I mean is this: we have no record of such coordination being engineered by humans, but that does not rule out the possibility that these ancient enemies have done it to each other countless times. We simply cannot understand it because we do not speak the language of bacteria or viruses.

The form of bacteriophage viruses matches the image we commonly associate with viruses: a tubular body like a spacecraft, with leg-like appendages spread around it like a spider. The virus injects itself through the channels exposed on the surface of a bacterium. After consuming all the bacterium’s resources, it causes the cell to burst.

Meanwhile, it integrates its own DNA into the genome of the host, multiplying itself. This doesn’t only happen in bacteria—viruses can do the same in human cells. Bacteria, on the other hand, can destroy viruses with the enzymes they produce, or by engulfing and digesting them.”

The professor realized the lecture was nearing its end.
“Let’s return to your question about the coronavirus,” he said, “or rather, let’s summarize our hypotheses.”

“Based on its symptoms and what we see under the microscope, this is a virus. According to unofficial reports, the outbreak did not begin in a single place, but appeared in multiple regions of the world simultaneously.From this, some conclude that coronavirus particles communicated among themselves, and activated collectively.

Of course, I am not dismissing the possibility of mutation, but for the reasons I stated earlier, I believe this virus had existed long before—its numbers were simply too small, and it remained dormant. It never drew attention because, among hundreds of thousands of virus species, it never stood out enough to be catalogued.”

He paused, then continued:

“What we do not understand is this: why did they suddenly awaken, reproduce at such speed, and overwhelm the human immune system? What changed in nature such that, like underground sleeper cells rising simultaneously, coronavirus colonies in different geographies mobilized and turned their weapons on humanity? That, I cannot answer.”

The lecture was over, yet the professor’s final words had already carved themselves into Teresa’s neurons. Richard brightened the moment he noticed her.

“I saw you in the paper this morning,” he said. “Thought to myself: Teresa claims she’s retired, but she’s still out there solving mysterious cases.”

“What paper? What story?”

Richard slid the newspaper across the desk with a grin.
“The thing about the cemetery. The ground opening up to the gates of hell.”

Teresa smirked.
“Of course. The sheriff can’t resist. He must have mentioned me in the article just to promote himself. I told that rookie a dozen times — don’t bring me up when the case is solved. But these kids never listen. They always think they know better.”

She waved the topic aside.
“Forget that. I need your help.”

“This time it’s not a supernatural mystery. It’s Mark.”
“My husband’s obesity worries me — and with this coronavirus on the horizon, I’m terrified. You know how badly it could hit people with his condition.”

The professor took a step back and looked her over from head to toe, as if examining a rare specimen.

“In an era where couples break up over petty arguments and abandon each other without hesitation, you travel all this way for a husband who, as far as I understand, isn’t even sick yet.”

He shook his head.
“That’s remarkable loyalty. No wonder people call you an idealist. But that’s not the only thing that surprises me.”

He paused, suddenly serious.

“You still live together, right?”

“Of course we do,” she replied. “A peaceful family requires its members to live together. And when they can’t—because of reasons beyond their control—they must at least remain united in spirit, transcending time and place.”

“As I suspected,” Richard murmured.

He lifted his right hand, turning the palm upward, then slowly rotated his wrist-down, then up again—an absent-minded gesture of emphasis.

“Forget obesity—you look as if you’re underweight. How does a man become obese while living with someone who barely has any mass at all? We often talk about a ‘family scale’ for a reason. Members of a household tend to influence one another—either growing heavier together or staying healthy together.”

“I don’t know the cause,” Teresa said. “But Mark is constantly hungry. Over just a few years he started eating more and more, and the weight followed. We’re both puzzled. What do you think could be behind it?”

Richard smirked.
“Who knows—maybe someone hijacked Mark’s brain with electromagnetic waves, controlling the lobe responsible for appetite.”

Teresa recognized the reference—the subtle nod to the strange case she solved in Bosnia. She answered with a faint smile:

“Well, even in a room with a jammer that blocks external energy waves and signals, his appetite doesn’t stop. So forget the jokes—what could really be causing this? You just described microbes communicating. Could an unknown bacterium or virus be doing something similar? Maybe a guest in the brain's appetite center—or gut bacteria consuming everything before Mark can?”

“For microbes, the brain is the most difficult territory to invade,” Richard replied.
“It’s like the headquarters of a nation: heavily guarded. The immune system protects the central nervous system with almost paranoid vigilance. Breaching the blood-brain barrier is no easy task.”

Teresa had learned, while unraveling the mysterious case of the confabulating refugee in Germany, that the brain was an exceptionally well-protected organ. Remembering that ordeal, she realized she had never come across a surgical report or case study describing a brain tumor—or any other lesion—triggering a heightened appetite. If such a phenomenon existed, it would likely stem from alterations in the primitive, animal brain. Yet multiple MRI and CT scans from different imaging centers confirmed beyond doubt that there was no abnormality in Mark’s central nervous system.

The professor, looking as though he had a suspicion in mind, continued with a serious tone:

“Did you do a DNA analysis? Who knows—maybe mutated cells are constantly sending hunger signals.”

Teresa answered, “It never crossed our minds, but… could something like that really happen?”

“There’s a reason I asked,” Richard said. “There is not a single recorded case of obesity caused by a mutation in DNA. What I’m really trying to point out is this: you know there are evolutionary scientists who claim that humans have no real will, that everything is predetermined, and therefore people shouldn’t be punished for their mistakes. To prove their theory, they focused first on the brain, then on hormones, and finally on DNA. But recent studies showed that human thoughts and decisions can influence hormone secretion—another blow to their theory. Still, they didn't give up. They’re still pushing forward.”

“So you’re saying Mark might have become obese because of some hormone malfunction?” Teresa asked, then added, “But I just learned his hormones are normal.”

Richard took the report from her hands, scanned it, and said:

“As I expected — only the hormones everyone knows and talks about have been measured. There are almost a hundred hormones. Unless you specifically request it, most of them get ignored. I’ll give you a list. Take it to a biochemistry lab, have them run the tests, and once we have the results, we’ll evaluate everything again.”

Teresa had returned home. She sent Mark’s blood and urine samples to the biochemistry lab along with the request sheet Professor Richard had prepared. By the time the courier left, Teresa was already immersed in research—searching through papers on hormones, tracing their subtle hierarchies, their secret rebellions, their silent dominions over the body. She had barely begun, yet she sensed she was stepping into a world far stranger than she had imagined…