How to Explain to a Five-Year-Old Child why we should “Test Test Test” for Coronavirus?

Igor Rudan
7 min readApr 5, 2020


I use this Story of a Tiger, a Vampire, an Engineer, and a Miner

Let’s think of each country in the world as a group of one hundred people. Working on their computers, they are doing a night shift at an office on the ground floor near a forest which harbors city zoo.

You can only enter this ground floor through a rather long corridor. It is also widely believed that a vampire wanders through the forest at night. Due to the proximity of wild animals and the rumors of a vampire, these one hundred office employees decided to protect themselves by developing a round ‘’net’’ made of very tough rope. They then tied one hundred bricks around the round edge of that net.

One night, a tiger escaped from the zoo. The office employees heard about it on the radio and hoped it wouldn’t come right to them, but they still pulled that net out of the closet. A moment later, the tiger walked right into their office. They threw the net at the tiger. Then, each one of them firmly gripped their brick on the edge of the net and pressed it down against the floor. As strong as it was, the tiger was now contained by this net. This was only possible through the joint action of one hundred people. The tiger couldn’t really do them any harm as long as each one of them pressed their own brick firmly against the floor. This is our current situation with coronavirus, this is how quarantine works to protect us against a deadly new virus.

However, all that the tiger wanted was to take away just one of those hundred persons and eat them somewhere in the woods. He would leave everyone else alone and return again in a year or so. The oldest and most ailing people were sitting next to the hallway door. Therefore, the tiger would probably drag one of them away. To protect one of these old persons, all one hundred had to hold their respective bricks pressed against the floor. It was not only tiring, but also very boring. Nobody wanted to live like that. But what else could they do?

Some began to slowly look at the elderly among them, wondering if they were really worth so much to them. Did it make enough sense to sacrifice the quality of life for ninety-nine of them just to save one old and already ill person? It was amazing that this virus had posed such a question to those hundred people in the 21st century. Their response to the tiger’s entry will reflect the value system of their society.

Still, everyone wondered how long they should keep this tiger pressed under the net and how to get out of that situation. Someone then remembered that there was a vampire in the woods, too. If the tiger was accidentally bitten by the vampire on the way to their office, then at sunrise, the tiger could simply disappear when it was illuminated by the Sun. This is analogous to the hope of the disappearance of coronavirus when the warmer weather arrives. So, it seemed reasonable to endure pressing those bricks against the floor for at least some more time. Then, one person asked the person next to them to press down their brick with their free hand, while they try to develop a rifle, with which they could simply kill the tiger. That would be an analogy for the discovery of a vaccine for this virus. Another person, however, also freed herself with the help of her neighbor. Then, she began to develop a fluid that would kill any appetite the tiger had. If he drank that fluid, the tiger would leave them alone and just walk away outside. This would be an analogy for the COVID-19 drug, which would reduce the need for respirators for the seriously ill and relieve the pressure on the health system.

Suddenly, there seemed to be as many as three options for this group — the disappearance of the tiger at sunrise, putting together a rifle, or the development of a fluid that would kill the tiger’s appetite. The problem is, there could be no certainty that any of those three measures would actually work. While waiting for the solution, people would become less likely to still press the bricks and hold the net. If only two or three loosened their grip in a similar place, the tiger would crawl out through that opening and then it would once again need to be caught in the net. However, more and more people, eager for a return to a normal life, were beginning to wonder whether it’s better to gamble with the 99 percent chance that the tiger would not grab them than to live like this, crouching down on the floor and pressing the net against the floor together with everyone else. This was especially the case for younger, faster and more adept people.

But suddenly, an engineer came up with another idea. He teamed up with the miner next to him. They asked their neighbors to hold down their bricks with their free hands, and the two of them walked out of the office and into the long corridor. The engineer instructed the miner to dig a tunnel under the corridor, which would lead back into the forest. While the miner was digging, the engineer placed ten large tiles to replace the hall floor. Each of those tiles had a sensor. The engineer installed a laser beam on the ceiling, which was alternately illuminating one of these tiles at a time. If the beam was directed at the tile sensor and the sensor didn’t register the beam, it meant that there was probably a tiger sneaking and standing on that very tile. Then, the tile would collapse and the tiger would fall down into the tunnel. He would then have to go back into the woods and sneak up on the group again from scratch. If the tiger ever managed to get through such a security system, the group would still have a tight rope with a bell stretched across the end of the corridor. It would alert the group that the tiger broke through their defense system and they would need to catch it once again in their net. But in the meantime, they would at least be able to live more normally and continue to do their work, regardless of the fact that there was a real tiger outside of their building. When the system was installed and tested, they pushed the tiger out together with their net, then let it keep falling through the floor tiles and into the tunnel again. Then, it would have to return to the forest each time and start sneaking up again from there. That’s how coronavirus testing works, in principle.

Virus testing is somewhat comparable to counter-espionage in war. We’re confronted with an enemy who is invisible, and we only become aware of the effects of its actions about a week later. In the meantime, we don’t know where the virus is and what it is doing behind our backs. SARS and MERS were significantly easier to control because the infected didn’t transmit the virus before the onset of coughing and other symptoms. With the novel coronavirus, the infection spreads during the incubation period, while the infected don’t have any symptoms. This is a big problem for us. But we can at least resolve it, somewhat, with more active testing.

If we allow it to, the virus will jump from the first infected person to two or three more people, then from each of them to two or three people again, and then do so again. That way, if the first infected person is drawn at the bottom of a piece of the paper, the wider and denser ‘’tree canopy’’ of infected people is constantly growing above his head. Through active testing, we’re able to find those who are infected among us. So, we constantly prune that “canopy” to make its branches as rare as possible. If the “canopy” ceases to grow very dense because we constantly prune its branches, then we’re in coexistence with the virus. We slowly develop immunity by exposure, we treat the seriously ill, and the number of people who have immunity for the virus grows, making it more difficult for the virus to find a new person to infect.

This way, it is possible to live with the virus present in the environment and still control the epidemic. When the Director of the World Health Organisation, Dr. Tedros Adhanom, suggests that we should “test, test, test”, he tells us that we must not constantly be on the defensive, in quarantine, and wait for people with symptoms to report for testing. That would mean that we’re constantly behind the virus. The enemy will then constantly surprise us and strike from somewhere. That’s why it’s important to test people as much as possible, but cleverly and reasonably so, and with clear goals.

There is only one thing to remember in any epidemic: we need to do find out who is infected and who isn’t, and then physically separate the infected people from the healthy ones. This should be done among the population, but especially in hospitals and retirement homes, where the virus poses the most danger if it enters the wards and corridors. Every action of separating the infected from the rest of the population makes it impossible for the virus to spread further. If we can be proactive in finding infected people and isolating them and their contacts, we will significantly slow down the spread of the COVID-19.

The novel coronavirus is currently spreading at a tremendous pace as each infected human can transmit it to two, three or even four healthy people with their next step. But if by taking an active approach to finding infected COVID-19 spreaders who don’t yet have symptoms, and by constantly separating them and all of their contacts and putting them into self-isolation, we manage to get to a situation in which one infected person manages to infect, on average, less than one healthy person, then we are all pretty safe. The epidemic will slowly go away on its own, and the vast majority of us will be able to live relatively normally. The minority, on the other hand, will constantly rotate in isolation and keep us all safe.


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Image credit: Jeffrey Eisen,

English Translation Assistant: Lauren Simmonds



Igor Rudan

Director, Centre for Global Health at the University of Edinburgh, UK; President, International Society of Global Health; Editor, Journal of Global Health;