Coronavirus: Where is patient zero?

Coronavirus: Where is patient zero?

Nowadays, everyone is asking themselves: Where is the Coronavirus’ “patient zero”? Let’s try to understand what the meaning of the question is and sketch out an answer.

What happens when a new disease occurs?

When a new disease occurs, it can become viral because the virus changes and acquires new characteristics which allow it to infect a new species. In our case, an important similarity was found between the coronavirus SARS-CoV-2 and bat’s coronavirus.

It is likely that the virus, in a favorable environment, underwent a mutation that allowed it to “skip” from one species to another and thus infecting humans. At that point, the first individual who gets infected is called “patient zero”.

Who is “patient zero”?

Patient zero is the individual who, after being infected with a new pathogen, started spreading the virus within a specific community. During an epidemic started by a new virus, the “patient zero” is generally the first person who was hospitalized because of this new disease and experiences peculiar symptoms that can be suspicious. It is at this point that researches begin, in order to understand the characteristics of the illness. Once the patient has been identified, an attempt is made to retrace its movements and contacts from the moment of infection to the moment of isolation.

Why is it important to identify “patient zero”?


Identifying patient zero is the only possible way to reconstruct all the steps that the virus took since the beginning of the pandemic. It can help us understand how the virus spread, the main ways of infection, and the forms of prevention that can be put in place. All the information collected contributes to reconstructing the behavior of the new pathogen and the characteristics of its spread. This also allows us to gain information, in order to plan actions to contain the epidemic as soon as possible.

We want to highlight that finding patient zero is not only useful at a clinical level: better treatment results, understanding which drugs are most suitable, or in designing a vaccine, 

but it is also useful in curbing the evolution of the epidemic while waiting for a cure to be found.

Why is patient zero so hard to find?

When the Coronavirus epidemic began in Italy, and the first case was reported, the experts began to reconstruct the whereabouts of that person, immediately identified as “patient zero”. However, the appearance of new outbreaks, that had no relationship with the first patient identified, wiped out any hypothesis of that individual being the origin of all subsequent cases.

In the frantic search for patient zero, all the contacts of the infected subject began to be investigated through rapid tests based on swabs. Gradually, the picture became more and more foggy because the search always came to dead ends. Finding the patient zero seemed increasingly difficult.

Determining the presence of the virus in the contacts is necessary to check if the test system used to identify the infected persons is reliable. Since the survival of the virus in the human body is limited, it was a real race against time.

Given that too much time had passed, it was very likely that patient zero, along with his/her initial contacts had already recovered from the disease, and therefore can no longer be identified with any screening.

Could there be more than one patient zero?

So now you might be wondering: Are we really sure that there is only one patient zero? What if those people who returned from Asia were actually asymptomatic and were thus capable of spreading the infection (and therefore passed the screening checks)?

To better understand this phenomenon, we must refer to the reproductive history of the virus within individuals. We have described that in many cases, the infection can be present despite the patient being asymptomatic.

As a matter of fact, it is one of the possible explanations, and also my personal belief.

If no links are found between the spread of an infection, this is a possible hypothesis. More than one infected person, probably traveling from Asia, could have entered Italy, perhaps even asymptomatic and unaware, and had contributed to the infectious outbreak.

The checks carried out through the temperature measurement system may not have been effective in hindering the creeping spread of the epidemic.

Multiple patient zeros are one of the possible interpretations of the early stages of the epidemic in Italy.






Med4Care Marco De Nardin

Marco De Nardin, M.D., Anesthesiologist, Critical Care Doctor









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