The "potentially pandemic" strain of flu they have found in China would not make the news under normal circumstances.

Yesterday the news came out: a group of Chinese researchers published in PNAS, one of the most prestigious magazines in the world, that they had discovered a new strain of influenza with "pandemic potential". The flu variant was infecting more and more pigs in the country, it could infect humans and, who knows, be the protagonist of the next great pandemic.

Or not. Not really. Although G4, as they have called it, is a strain (of avian matrix) for which humans would not have immunity and, indeed, it could mutate to be transmitted with great ease in humans, the truth is that it has been in pigs for years and does not appear to cause significant symptoms. Despite the bombastic headlines, it is yet another virus. As Robert Webster, a researcher specializing in this disease, explained in Nature, "we just don't know if a pandemic will occur until it occurs."

What do we know about the G4 strain?

This strain is the result of a process that is usually called "rearrangement". When several influenza viruses coexist in the same organism, a genetic exchange phenomenon can occur that generates new strains. This seems to be the case: G4 is the result of the combination of three lineages: one similar to the typical flu of Eurasian birds; another related to 2009 H1N1; and finally, a North American variant of the latter that incorporated swine flu genes.

As part of efforts to control zoonoses, the team led by Liu Jinhua of the China Agricultural University (CAU) have analyzed some 30,000 nasal swabs taken from pigs in slaughterhouses in 10 Chinese provinces (and another 1,000 sick pig swabs examined in your school's veterinary hospital). The samples yielded 179 swine flu viruses. The vast majority of which were subtypes of this strain or any of the other five that make up the Eurasian G avian lineage.

This means that, on paper, the G4 is a candidate to be closely watched. After all, the H1N1 strain has already gotten its way more than a decade ago and put the world on the brink of a truly critical pandemic. However, it is advisable not to take this type of study out of context. Firstly, it should not be forgotten that, although the flu spreads easily from pigs to humans, these strains rarely have the ability to spread from human to human.

Second, this is part of the usual work of virologists. It is not unusual for viruses with "pandemic potential" to appear. A few weeks ago, it was announced, for example, that hundreds of SARS-CoV-2-like coronaviruses had been found in Chinese jungle bats. That is to say, very probably under normal conditions neither of the two news items (neither that of the coronaviruses, nor that of the G4); This has been the case with hundreds of identical studies in recent years, but we do not live in normal conditions.

Are we really facing a "potential pandemic"?

As Webster said, we don't know what a pandemic will be until we have a pandemic, and therefore theorizing about possible mutations of the G4 that is moving among Chinese pigs is quite free. It might make sense, as the study authors point out, to move forward in vaccine development and in the strain study in order to get some work done in case we detect a major change. But, beyond that, little else can be done besides monitoring the circulation of the strain.

However, we must bear in mind that we live in times especially sensitive to this type of news and discoveries. As occurred, for example, in the context of the 2019 summer listeriosis outbreak and the boom in interest in this type of health problem, it is reasonable to think that the public interest will decline as the crisis loses strength.

Therefore, in general, we must be careful with these types of studies because they can generate a feeling of "Pedro and the Wolf" and erode efforts to improve early warning and monitoring systems. No one knows how we will get out of this crisis and, precisely for this reason, it is convenient to be clear about what and when something is a threat. And it is that even being scrupulous, epidemics always have the capacity to surprise us.

Image | Kenneth Schipper

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