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lite.cnn.com - on gopher - inofficial | |
ARTICLE VIEW: | |
Spikes of flu virus in wastewater raise questions about spread of bird | |
flu | |
By Brenda Goodman, CNN | |
Updated: | |
1:36 PM EDT, Tue April 30, 2024 | |
Source: CNN | |
Spikes of influenza A virus seen in wastewater samples from 59 sewer | |
systems across 18 different states this spring may point to the spread | |
of the H5N1 avian influenza virus that is currently infecting dairy | |
cattle, a new study suggests. | |
So far, the US Department of Agriculture has reported more than 30 | |
herds of dairy cows infected with H5N1 influenza across nine states. | |
But there are questions about how large the outbreak might be and | |
whether the US can adequately track it. | |
In a news conference last week, USDA officials admitted that it’s | |
been difficult to get milk producers to let them test for the | |
infection. Recent tests of milk purchased at grocery stores found | |
genetic material from the H5N1 virus in , though further testing showed | |
the virus fragments detected in milk were not infectious. | |
Last week, in a multi-agency news conference on the government’s | |
response to the spreading virus, Dr. Nirav Shah, principal deputy | |
director of the US Centers for Disease Control and Prevention, said the | |
agency was looking at whether it might be feasible to use wastewater to | |
pinpoint areas where the virus is spreading. First, he said, scientists | |
would need to develop a test that could distinguish H5 influenza from | |
the larger soup of circulating A-strain flu viruses. | |
Now scientists at Emory, Stanford and Verily Life Sciences, a research | |
organization affiliated with the WastewaterSCAN network that monitors | |
a large network of wastewater treatment plants across the US, say they | |
have done just that. | |
Wastewater testing is a passive way of tracking the spread of | |
infections. It doesn’t depend on people or animals to be swabbed to | |
test for pathogens. Instead, evidence flows into the wastewater every | |
time a toilet is flushed or someone dumps material down a drain. | |
Out of 190 wastewater treatment plants that currently monitor sludge | |
samples for influenza A, 59 saw increases of the A-strain viruses this | |
spring, just as human flu cases were flat or falling. Wastewater | |
experts wondered if it might be from H5N1, the highly pathogenic avian | |
influenza infections in dairy cattle or other animals. | |
The WastewaterSCAN team developed a test to check for the flu virus’ | |
H5 gene and used it on stored samples from sewer systems near areas in | |
Texas where dairy cattle had tested positive, but not including | |
wastewater directly from the farms. | |
The team measured both a genetic marker for influenza A viruses and | |
genetic markers specific to H5 viruses. | |
As levels of the marker for influenza A viruses began to rise in early | |
March, the markers for the H5 viruses began to rise in tandem. The | |
concentration of the H5 gene in the samples was nearly as high as the | |
concentration of the influenza A viruses overall, suggesting that a | |
large fraction of the viruses in the samples were H5N1. | |
What’s more, the concentrations of influenza A viruses measured in | |
these wastewater sludge samples from the Amarillo, Texas, area were | |
“among the highest ever measured in wastewater,” the study noted. | |
The stored sludge samples tested for the study were taken between | |
February 4 and April 16 at two treatment plants sites in the City of | |
Amarillo watershed, and a third wastewater treatment plant in Dallas | |
County. The researchers confirmed wastewater processing plants sampled | |
in the Amarillo area permitted some producers to dispose of animal | |
byproducts, including dumped milk from dairies, which may explain the | |
high concentrations of influenza A viruses, and H5 viruses in their | |
samples. | |
Just as wastewater testing has proven to be a harbinger of rising | |
Covid-19 infections in the past, researchers say their study suggests | |
it could be an early warning for bird flu outbreaks in farm animals, | |
too. | |
“We detected the H5 marker right before there was confirmed highly | |
pathogenic avian influenza in those counties,” said Dr. Alexandria | |
Boehm, who is a professor of civil and environmental engineering at | |
Stanford University. | |
“I think that is super interesting. It means that the wastewater in | |
this particular case, with this particular pathogen, can reveal | |
information about what was circulating in these cattle before there was | |
information publicly available,” Boehm said. | |
The paper was on the BioRxiv server, ahead of rigorous review by | |
outside experts. The researchers say they are working to get it | |
published in a scientific journal. | |
The study authors stress that no H5N1 outbreaks in cows have been | |
reported in any of the sewersheds they tested. Instead, they think | |
that the permitted dumping of milk likely caused the big spikes in H5 | |
virus they saw in early March. | |
The researchers note that they can’t rule out that the H5 genetic | |
material they’re picking up in the wastewater is all from dairy | |
cattle. It could also be from birds or even humans. | |
The researchers say they also don’t have enough information to know | |
where the increases in influeza A virus are coming from across multiple | |
states. | |
“We don’t know the answer to that question. It is something that I | |
think needs to be followed up on,” Boehm said. | |
But if the spike in viruses is from dumped milk or other animal waste | |
across the sewersheds they monitor — and that’s still a pretty big | |
if — it means the outbreak is likely far more widespread than is | |
currently known. | |
“If dairy industry activities in these sewersheds are a primary | |
source of H5 in wastewater, this suggests that there may be additional, | |
unidentified outbreaks among cattle with milk sent to these facilities | |
since milk from infected animals is required to be diverted from the | |
food supply,” the study authors note. | |
But the researchers also say their results should be interpreted | |
carefully. Without tracking down possible sources in the sewersheds | |
they monitor, the source of the virus can’t be proven. | |
“However, multiple lines of evidence suggest animal sources,” the | |
paper says. | |
The researchers say their testing method is very sensitive. It can | |
detect even small amounts of the genetic material from the H5 viruses, | |
but they can’t tell if the viruses would be able to infect people and | |
make them sick. Boehm says they didn’t try to culture the virus to | |
see if it could infect cells. | |
The US Food and Drug Administration said last week that it has been | |
testing samples of pasteurized milk in which traces of the H5N1 virus | |
have been detected and so far found the milk is not infectious and | |
cannot make people sick. | |
The wastewater researchers acknowledge that it’s also possible that | |
their tests are picking up other types of H5 viruses, including | |
low-pathogenic H5 influenza viruses, but they say these are not | |
expected to be circulating in these areas at this time. | |
“This is a situation where we really felt like we were ethically | |
bound to share this information with colleagues through a preprint and | |
get the conversation going, because there are unanswered questions that | |
are really important to answer,” Boehm said. | |
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