Texas' wastewater monitoring reveals an early indication of the bird flu outbreak.

Texas' wastewater surveillance detected an early indication of the bird flu outbreak.

Imagine a scenario where a potential pandemic-causing virus turns up in the wastewater being monitored. Or picture the bird flu, H5N1, which has already killed millions of animals and nearly 500 people out of the almost 900 it has infected over the past two decades.

This was the hypothetical situation pondered on a Monday. By midweek, Hanson's coworker, Dr. Michael Tisza, a virologist and microbiologist from the Baylor College of Medicine in Houston, was raising the alarm.

This time, it wasn't just a drill.

"Mike called me and said, 'I think I found it,'" said Hanson, a UTHealth Houston epidemiologist who uses big data and genomics to study infectious diseases.

This occurred on March 7, about three weeks before the US Department of Agriculture revealed that H5N1 had infected dairy cows in Texas for the first time.

A novel approach to wastewater monitoring

Over the past two years, Texas Epidemic Public Health Institute (TEPHI) employed a different method for wastewater monitoring. Instead of focusing on specific viruses, the Texas researchers chose to utilize advanced techniques and computers to sieve through the vast genetic material found in their wastewater samples. Through this method, they can discover known viruses as well as the unexpected.

Dr. Anthony Maresso, a molecular virologist and microbiologist from the Baylor College of Medicine, envisioned this system. He explained, "We can capture every known virus in the sample, and then the computational team will analyze the data comprehensively and detect multiple viruses, which is the benefit of what we're doing as opposed to other locations."

Three other organizations also studied the possibility of H5N1 in wastewater.

The WastewaterSCAN network, spearheaded by researchers from Stanford, Emory Universities, and Verily, recently published a preprint study that identifies the H5N1 virus in wastewater by seeking out one particular portion of the virus.

In addition to this first discovery, the team has since analyzed three more sewer systems: one near a known H5N1 cattle outbreak in North Carolina, one in a California city experiencing an unusual surge of human influenza A cases, and one in a Hawaiian city with no dairy processing plants or reported cases of highly pathogenic avian influenza. In all three cases, the test produced accurate results. WastewaterSCAN plans to incorporate this test into all 190 wastewater sites they monitor.

The CDC likewise introduced a dashboard displaying locations where influenza A viruses are detected in an unusually high quantity.

Given that H5N1 is an A strain of the influenza virus, like certain types of seasonal flu, detecting A strains now during the offseason is an effective proxy for H5N1. However, this method will be less helpful when influenza A picks up again in the winter.

TEPHI's system, on the other hand, could potentially function as the first indication of new viruses—the elusive goal of pandemic prevention. Since they began monitoring in 2022, the team has identified over 400 viruses in Texas wastewater.

Insights from toilet flushes

Unlike sampling bodily fluids, wastewater monitoring is passive and does not require consent or even a person accessing a clinic or emergency room. Data is gathered whenever someone flushes a toilet or following the treatment of agricultural waste, such as disposing of unused milk.

The main downside of wastewater monitoring is its inability to pinpoint the source of the pathogen.

Since March 4—the date the H5N1 pathogen was initially discovered by the TEPHI team—it has been detected in nine Texas cities and 19 of the 23 sites they monitor. They didn't identify the cities they tested in their study but did inform local public health authorities and the CDC of their findings.

Their study was recently published as a preprint, pending review by external experts.

Sweeping mystery behind the source

"We don't really know where it's coming from," said Dr. Eric Boerwinkle, the dean of UTHouston School of Public Health and TEPHI director.

"We all have our own theories," he said, adding that Texas is in the path of two major flyways for migratory birds and boasts a vast agricultural industry with chickens and cows.

Yet, H5N1 has been devastating both wild and commercially bred bird flocks in the US since 2022 when TEPHI began monitoring wastewater, and the group hasn't detected any traces of it in their samples before now.

"Obviously, something different now," Tisza said, "is that it's commonly infecting dairy cows."

A single case of H5N1 has been confirmed in relation to the bovine outbreak. The individual, a farmworker with close exposure to infected cattle, contracted notable eye inflammation (conjunctivitis), but no breathing difficulties or congestion. Medical professionals treated the individual with antiviral medications, and they have since entirely recuperated.

Officials from the Centers for Disease Control and Prevention (CDC) claim that the overall risk to the general public remains minimal. Nevertheless, they continue to track the situation cautiously.

The United States Food and Drug Administration (FDA) completed a more comprehensive review of 297 dairy samples from grocery stores across the nation. The results, which were published on Monday, revealed that fragments of the H5N1 bird flu virus were present in 15 of the 38 states where these products were manufactured. It was disclosed that nearly 1 in 5 samples exhibited some traces of the virus, suggesting that the issue might be more pervasive than previously estimated.

Dr. Maresso of the Texas Environmental Protection and Health Incident (TEPHI) expressed skepticism, noting that it may not relate to the actual spread of the virus. Despite this, he remarked that there haven't been significant increases in influenza cases in hospitals, which could signify severe infections.

"If it were just one or two sites and we had some dairy or other processing plants located close to them, that could explain things," Maresso said. "But we've basically detected the signal in all those points, even in large cities that aren't near dairy farms."

In terms of the Texas situation's current state and future trajectory, Dr. Tisza felt noncommittal. Initially, he said, there were some cities that the group monitored with a H5N1 signal as potent as that seen during the flu season. However, in general, the signal has only been about 25% of that strength, he noted.

"It's sort of at a plateau right now," Tisza explained. "It's not increasing, and it's not going away. That, in and of itself, is intriguing." Tisza mentioned that they would provide an update if there's a substantial spike.

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In the context of the bird flu outbreak, a novel approach to wastewater monitoring using advanced techniques and computers could potentially identify unknown viruses early, such as H5N1. This method, employed by Texas Epidemic Public Health Institute (TEPHI), allows for the discovery of known viruses as well as the unexpected.

Given the inability to pinpoint the source of the pathogen through wastewater monitoring, many organizations, including WastewaterSCAN and the CDC, have employed various methods to detect H5N1 in wastewater. WastewaterSCAN, for instance, seeks out a specific portion of the virus to identify its presence, while the CDC uses detecting influenza A viruses in unusually high quantities as an effective proxy for H5N1 during the offseason.

Source: edition.cnn.com