Detection of H5 in wastewater may have offered early bird flu warning
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Key takeaways:
- Wastewater surveillance could have revealed the spread of H5 influenza before official confirmation in birds, cows and humans.
- Monitoring wastewater may help public health officials respond to outbreaks quicker.
LOS ANGELES — Public health officials could have detected H5 influenza in wastewater days before highly pathogenic avian influenza was confirmed in cattle earlier this year, according to a study presented at IDWeek.
“One of the most important parts to public health responses is having the time to implement them and being prepared,” Alessandro Zulli, PhD, postdoctoral researcher in civil and environmental engineering at Stanford University, said during a media briefing ahead of the conference.
“That’s really where wastewater monitoring can help with these things,” Zulli said. “All of our detections in the wastewater were often days ahead of when it was actually detected in cattle, because cows don’t really go to the doctor.”
This year, H5N1 influenza has affected more than 103 million wild birds, poultry and backyard flocks and 323 dairy herds in the United States, according to the CDC. There have been 25 reported cases in humans in five states — 11 in California since Oct. 3. Most cases have had a reported contact with cattle or poultry, but one person in Missouri had no known exposures.
Although wastewater surveillance is not new, it attracted more interest during the COVID-19 pandemic. The CDC, which monitors wastewater for influenza A viruses as part of its regular year-round surveillance, added an online dashboard in May to help track the potential spread of H5N1.
For their study, Zulli and colleagues developed an assay that enabled them to differentiate H5 viruses from other influenza A viruses in wastewater. According to the researchers, it demonstrated 100% specificity and 90% sensitivity in detecting H5 viruses based on testing against clinical specimens, including other influenza A viruses.
The assay identified 59 wastewater treatment plants with increases in the H5 this year that coincided with the bird flu outbreak in cattle. In three Texas plants, retrospective testing using the assay showed that H5 was present before the official confirmation of H5N1 in cattle or the first human case in Texas, according to Zulli and colleagues. The source of the H5 viruses was likely animal processing facilities, they found.
Detecting viruses in wastewater offers public health officials time to build a response and understand how a disease is spreading, Zulli said. Because a system for collection and analysis of water samples already exists, the time to response could be significantly sped up, he said.
“To me, wastewater monitoring remains the fastest, most unbiased method to actually measure the prevalence [of viruses] among the population, and leveraging this could have enormous implications for understanding the spread of illnesses and implementing interventions,” Zulli said.
References:
- Zulli A, et al. Abstract 309. Presented at: IDWeek; Oct. 16-19, 2024; Los Angeles.
- CDC. Avian influenza (bird flu): CDC A(H5N1) bird flu response updated October 11, 2024. https://www.cdc.gov/bird-flu/spotlights/h5n1-response-10112024.html. Updated Oct. 11, 2024. Accessed Oct. 18, 2024.
- CDC. Avian influenza: H5 bird flu: Current situation. https://www.cdc.gov/bird-flu/situation-summary/index.html. Updated Oct. 16, 2024. Accessed Oct. 18, 2024.
- CDC. National wastewater surveillance system (NWSS). https://www.cdc.gov/nwss/rv/wwd-h5.html. Updated Oct. 12, 2024. Accessed Oct. 18, 2024.
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Zulli A, et al. Abstract 309. Presented at: IDWeek; Oct. 16-19, 2024; Los Angeles.
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