The long-awaited WHO report (World Health Organization) on the origin of COVID-19, published today after 28 days of fieldwork by experts in Wuhan (China), presents four possible theories on the appearance of the SARS-CoV-2 coronavirus in humans, without ruling out any completely.

However, the report clarifies that some of the theories are more likely than others, highlighting that it is necessary to continue the investigation of all of them.


The report considers “very likely“That the coronavirus that causes COVID-19 reaches human beings from an animal that presents coronavirus very similar (maybe a bat or a pangolin) but not directly, but through of one or more intermediate animals.

Although the SARS-CoV-2 DNA is 96% similar to another coronavirus detected in the horseshoe bat, experts consider that the evolutionary distance between one virus and another is “several decades“, Which suggests a”missing link“, Possibly variations formed in other animals before in man.

Against this theory is the fact that no evidence of SARS-CoV-2 has been found in many of China’s farm-raised domestic and wild animals.


The WHO report did not consider the possibility of a deliberate release of the coronavirus, previously ruled out by other experts after analyzing the SARS-CoV-2 genome.

An involuntary release in the laboratory could be plausible, since “although they are rare, accidents do occur and several laboratories in the world work with coronavirus “, says the study.

The report indicates that the coronavirus bat mentioned, the one closest to SARS-CoV-2, was studied in the Wuhan Institute of Virology and that the cities’ disease control center moved on December 2, 2019, a time when laboratory work can be disrupted.

However, the report notes that the three laboratories of Wuhan that they studied coronavirus they had high levels of biosafety, that no incidents were reported in the December 2 move, and that no genome in them was identical to SARS-CoV-2.

All this makes “highly unlikely“The theory of the origin of the pandemic in a laboratory, concludes the report.


In a probability middle term between the two previous theories, there are two others: direct transmission from an animal to man or contagion through the food chain, perhaps by frozen food it could even come from countries other than China.

The document adds that, although in some countries human beings consume bats O pangolines, there is no direct evidence of transmission of the coronavirus in this way, nor was meat from them detected in the markets of Wuhan.

On the fourth theory, which considers the food chain as a transmitter, the report admits that China had in 2020 outbreaks of the coronavirus that causes COVID-19 related to frozen meat from other countries and it has been verified that this and other coronavirus they can survive in low temperatures.

The WHO report mentions about wastewater studies in countries such as Spain or Italy that detected the presence of SARS-CoV-2 before December 2019, when the first cases of COVID-19 were registered in Wuhan.

However, contrary to this theory, it is indicated that the concentration of coronavirus found in frozen foods was very low and that it would be very strange if the virus was already circulating in the food chain before large outbreaks of transmission between humans had been detected.

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