The avian flu epidemic that broke out in US cattle farms shows no signs of abating. In fact, it could be more extensive than expected. A recent document from the Food and Drug Administrations seems to suggest that the American agency has identified traces of the genetic material of the H5N1 virus in pasteurized milk on the market in the United States. News which, if confirmed, could indicate that the infected herds are much more than those currently identified by the health authorities.
The conditional, in this case, however, is a must, because the language used in the FDA note is more cryptic than ever, and the communications of the previous days from the American surveillance bodies had always stated that the contaminated milk samples they came solely from cows with a confirmed infection, which by law are not permitted to be sold for human consumption.
Avian flu, the epidemic is more extensive than expected
If the new document really admits the presence of viral residues in milk marketed in the USA, as several American newspapers and experts report, the implications would be mainly epidemiological. Since the sale of milk from sick animals is not permitted, finding it in supermarkets would mean that there are many infected animals that escape the radar, and that the epidemic is therefore much more widespread than expected.
In terms of human health, the experts' concern is obviously related to exposure to the virus, and therefore to the possibility of infections in humans which would help the virus to progressively adapt to our species. In this sense, however, the FDA is explicit in reassuring us from the risks: pasteurization – they write – has always proved sufficient to neutralize viruses and bacteria, and there are no clues that lead us to suspect a different (and therefore unique) situation in the case of the H5N1 virus.
The tests used to identify the presence of a virus in a sample, the PCR that we have learned about during the Covid-19 pandemic, work by amplifying any small fragment of the virus present in the sample. And therefore they do not allow us to distinguish a viable and infectious virus from a fragment of inactive virus, or from the RNA produced during the infection. To establish the presence of viral particles capable of causing an infection, another type of test must be used, in which the viruses are incubated and then tested on a living cell.
Analyzes which – writes the FDA – are being carried out, but which for now have not produced results that suggest that the milk supply chain, if pasteurised, could put human health at risk. Despite the reassurances, obviously, we can only hope that the American authorities will keep their guard up and manage the epidemic with maximum transparency. Because the more a virus has the opportunity to come into contact with our species, the greater the chance that it will acquire the ability to infect us and transmit effectively between human beings. And in that case – we saw it in the initial stages of the pandemic – the lack of transparency can produce catastrophic damage.
In fact, to date we do not know whether milk can be a vehicle for an infection which to date has always been transmitted via the respiratory route. However, experts explain that those who work with cattle should consider using protective masks: high-pressure spray nozzles can aerosolize virus-containing milk from the milking parlor. As for the effectiveness of pasteurization, we warn about the possibility of viral agents surviving in fat globules.