Avian flu, H5N1 virus in the sewers: what the experts say

The H5N1 avian influenza virus detected in the wastewater of 9 cities in Texas (USA) in the period between March 4 and April 25, when H5N1 outbreaks in cattle farms and one human case were recorded. The population affected is millions of inhabitants. This is what researchers from the Baylor College of Medicine (Houston) discovered in a pre-publication work on ‘MedRxiv’. According to scientists, “genome analysis of sequences found in wastewater suggests the avian or bovine origin of H5N1 but other potential sources, particularly humans, could not be ruled out“.

“The increasing presence of the H5N1 virus in domestic animals raises significant concerns that viral adaptation to immunologically fragile humans could result in the next influenza pandemic,” the study recalls. “Wastewater-based epidemiology (WBE) is used to track viruses and in the past it has been used for polio and was recently implemented for monitoring Sars-CoV-2 during the Covid pandemic”.

What the experts say

The American study “tells us that the avian virus is present in feces, obviously, but we don’t know whether it comes from cattle or humans. What makes me think is that they could be asymptomatic cattle and this could be worse. It’s not a good sign to know that there could be this possibility”, the epidemiologist tells Adnkronos Salute Massimo Ciccozzi.

Wastewater-based epidemiology (WBE) “is a good indicator”, states the epidemiologist, specifying that “in this case there is not the whole virus but pieces of the viral or bacterial genome, so those who carry out the analyzes must be experts in reconstructing the genome of the virus and identifying it as such. It is fine as an epidemiological technique for viruses expelled in the feces”, concludes Ciccozzi.

For the virologist of the State University of Milan Fabrizio Pregliasco, the discovery of the H5N1 avian influenza virus in the wastewater of 9 Texas cities “is quite worrying because it highlights an enormous spread of the virus. A wider spread than that photographed by the reported infections”. Pregliasco hypothesizes hidden cases, “probably also in humans”.

This work by the researchers “is a further signal of the need for stringent surveillance”, underlines the virologist. And the confirmation, he adds, of the “great potential” that wastewater analysis has “to evaluate the spread of viruses” such as H5N1, as well as “chemical substances such as medicines or drugs”.

“First in milk, now in wastewater.” For the infectious disease specialist Matteo Bassetti It is “a very bad sign” to have found the H5N1 avian influenza virus in the sewers of 9 Texas cities. This tells us that “the virus is very, very close to us”, that “it is much closer to humans than we could have thought until a month ago”, explains the head doctor of the San Martino Polyclinic in Genoa to Adnkronos Salute.

The waste water analysed, observes the expert, “it is likely that it certainly concerns agriculture and livestock, but also human beings. In fact, it is waste water coming from the biological fluids of animals, but potentially it could also come from other animal species, perhaps not yet evaluated, or by man”. It is no coincidence for the authors of the article, if it is true that “the genome analysis of the viral sequences detected in wastewater suggests the avian or bovine origin of H5N1, it was not possible to exclude other potential sources, in particular l ‘man”.

“Unfortunately I find that the attitude of many in our country is truly dangerous and wrong”, warns Bassetti. “We still have many people who think that Covid was an invention – he underlines – and that when we talk about these problems we do so only because we like to alarm people. Here, in the face of this attitude, with so much of the printed paper and evidently also from politicians who are taking on great responsibilities” in this sense, “I believe that if by chance the avian flu were to arrive in our country too, many heads would roll”. The discovery of the H5N1 virus in the sewers, warns the specialist, should be “not an alarm signal, but certainly an invitation to keep our antennas straight, because something could happen”.