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Shortly before the Institute of Public Health processed the first positive sample of Covid-19, the Minister of Health, Jaime Mañalich, spoke of a countdown: “This pandemic is approaching our country. I think it will come very soon, “said the authority.
So it was. Six days later, after Brazil and coinciding with Argentina, on March 3, in Talca, a newly arrived doctor from Southeast Asia became the first patient diagnosed with coronavirus in Chile.
However, was he really the first, the so-called “case zero”? In light of new data provided by the ministry’s epidemiological reports, everything indicates that it is not. In fact, there is already a record of at least 13 people who developed the symptoms in advance, which places their infections in mid-February. With this in view, one already has a certainty: in February, a month before its official debut, the coronavirus had already been installed in the country.
As of April 15, the Ministry of Health made a change in the case reporting methodology in the Covid-19 epidemiological reports. From now on, the infections reported in the 346 communes of the country began to be registered according to the date of appearance of symptoms, and no longer due to the date of confirmation of the diagnosis (with positive PCR examination).
The modification, supported by epidemiologists who carry out field studies, showed that in epidemiological week 9 (which runs from February 23 to 29), 13 people manifested the symptoms of coronavirus, in towns such as Calama, Ñuñoa, Linares. , Concepción and Punta Arenas, which were subsequently confirmed with the test (see table).
In other words, the hitherto “case zero” can still be classified as the first positive test carried out in Chile, but no longer as the first coronavirus carrier on our borders.
According to the experts, these 13 people – all travelers – could have started the symptoms days before returning to Chile, while they remained in the country of visit where they were infected, or a few days after their return.
For the government, there is no doubt. Consulted the minister Mañalich on when the coronavirus arrived in the country, he maintains that “the data that I handle is that it was in the middle of last February.”
A relevant point is that the date of the onset of symptoms is given by the patient and recorded by the treating physician on the Epivigila epidemiological registration platform. In other words, these people, who were symptomatic, consulted in a healthcare center already in the country, and after March 3.
The infectologist from the University of Chile Jeannette Dabanch, consulted for this phenomenon, goes back 11 years, to 2009, to exemplify with AH1N1 in Chile.
“The first positive PCR test for influenza AH1N1 was detected in Santiago, on some travelers who came from the Dominican Republic. And the next day another positive case appeared in a boy from a school in the eastern sector of the capital. There we concentrated in Santiago, looking for cases and contacts, to see if we could establish the appearance of the onset of symptoms. And when the start of the pandemic in Chile was already established, we realized that, in reality, the first case had passed us by and had happened in Puerto Montt, ”he says.
Dabanch points out that this is not a behavior typical of the coronavirus, but it happens in all pandemics. After the confirmation of the first patient with a positive test for a new virus, a retrospective search for cases begins, which can only be approached approximately, keeping a correct and meticulous record of the date of onset of symptoms.
Mañalich also reconstructs the milestones prior to the arrival of Covid-19: on January 30, the first Covid-19 PCR test was carried out in the country at the Institute of Public Health, and during the month of February more than 10. All negative, until March 3 last.
“This has happened in all countries, and that is why we cannot identify the ‘case zero’, the same as what happens in China and elsewhere. We cannot resolve the question of who was actually the first person. And for that reason, we did not identify the Talca doctor as patient zero, because it was later discovered that the virus actually existed before, and must have come the same way, from a trip abroad, “he stresses.
The epidemiologist at the Universidad del Desarrollo, Manuel Nájera, indicates that these data should be viewed with caution. “All these first symptomatic cases correspond to the PCR cases that were confirmed in early March. In general, they are people who came with symptoms from Spain (Europe), which is the place where the majority came from at first. We must remember that the first week of cases, all of them were imported cases, of trips abroad ”.
According to what is published in the most recent epidemiological report of April 28, in the Metropolitan Region, by the last week of February two people living in the commune of Santiago had already started symptoms, one in La Reina, the other in Ñuñoa, Pudahuel and San Bernard.
Even, in the previous report, published on April 25, Calama records another case, but with onset of symptoms in epidemiological week 8 (between February 16 – 22). The same happens in Las Condes and Vitacura. Mañalich explains that this change in the visualization of the cases was made, precisely, in order to have a more reliable approach to the actual onset of the disease in the country: “At that time it could happen that the person was five days with symptoms and the problem is that during those five days it was contagious. We were very interested in knowing the start date well to be able to identify what risk a place has. ”
The authority explains that the time difference between the onset of symptoms and the subsequent diagnosis of these cases lay in the lack of awareness before the first media case. “They are people who had not given importance to their symptoms because they were mild, perhaps bronchitis. They did the exam and they did have coronaviruses, ”he says.
However, the experts agree that it is difficult to determine a single zero patient, but rather that what is relevant is to reach a consensus start date for subsequent studies. “The important thing is that this data is being rescued to at least know that the disease was introduced before,” concludes Dabanch.
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