#18,292
Four months ago we saw a preprint from researchers at UTHealth Houston and Baylor College of Medicine reporting the detection of avian H5N1 in wastewater from 9 (unnamed) Texas cities - starting last March - whose rate exceeded that of seasonal influenza viruses by April.
While the origins of these viruses were thought to be primarily from avian or bovine sources, some contributions from humans could not be excluded.
Since then we've also looked at the CDC's more generic Influenza A wastewater surveillance, and Wastewaterscan.org's less robust, but more specific surveillance for H5 in wastewater. Each provides us with important data, but many significant gaps in our knowledge remain.
Yesterday the researchers at UTHealth Houston & Baylor College of Medicine had a correspondence published in the NEJM on their continued surveillance of wastewater across Texas, which urges wider surveillance for H5N1.
The lead author, Mike Tisza, tweeted:
First a link to the brief correspondence, followed by excerpts from a UTHealth Houston press release. Follow the links to read them in their entirety. I'll have a postscript after the break.
CORRESPONDENCE
Sequencing-Based Detection of Avian Influenza A(H5N1) Virus in Wastewater in Ten Cities
Published September 11, 2024
Avian flu found in wastewater of 10 Texas cities through virome sequencing by researchers at UTHealth Houston and Baylor College of MedicineWritten by: Deborah Mann Lake | Updated: September 11, 2024
Avian influenza A(H5N1) virus, which spread to cattle and infected 14 people this year, was detected using virome sequencing in the wastewater of 10 Texas cities by researchers at UTHealth Houston and Baylor College of Medicine. The virome is the collection of viruses in a sample, in this case a wastewater sample.(Continue . . . )
The information was published in the New England Journal of Medicine.
Until March 2024, H5N1 had not been detected in 1,337 wastewater samples analyzed by the team. But from March 4 to July 15 (the end of data collection for this article), H5N1 was detected in 10 of 10 cities, 22 of 23 sites, and 100 of 399 samples. However, the abundance of H5N1 in wastewater samples collected over time did not correlate with influenza-related hospitalizations over the same time period, so the risk to the public was extremely low.
UTHealth Houston and Baylor established the wastewater testing program as part of the Texas Epidemic Public Health Institute (TEPHI).
The sequencing protocol used by the team can detect genetic changes that might indicate an adaptation of the virus to mammals, perhaps even humans. Lack of clinical burden in humans and genomic information suggested that the source of the virus load found in wastewater during that time span came from animal origins. But continued surveillance is critical for monitoring any evolutionary adaptations that would indicate the potential for it to jump to humans, the researchers concluded.
We are rapidly approaching 6 months since we first learned of HPAI H5 in American dairy cows - which by that time had likely gone undetected for months - and we have yet to get a good handle on how widespread the virus is across the nation, primarily due to a lack of testing.
Yesterday, California - the largest dairy producing state in the nation - announced 3 more herds infected, but so far, they are not mandating testing.
Colorado, which is the only state currently requiring weekly bulk-milk tank testing, has had to re-quarantine herds which tested positive after being previously released; a clear demonstration of the value of continued testing.
Despite industry assurances that `sick cows' are immediately removed from the production line, and `infected milk never enters the food chain', dairy products on the shelf have obviously tested positive for (heat-inactivated) HPAI virus particles.
We've also seen credible reports of asymptomatic infection in cattle. But testing remains voluntary, and many dairy farms fear the negative publicity and economic impact that would come from having a positive test result.
We've also seen multiple anecdotal reports of sick farm workers who were never tested for the virus (see here, here, and here), and media reports (see here, and here) that some states have been less than cooperative with CDC and USDA investigators.
Two days ago, in an article on Missouri's H5 case, the Kansas City Star reported:
Details about the patient have been sparse to protect their identity, but some experts have found the state and federal response to be frustratingly slow. For instance, while CDC labs confirmed the avian flu diagnosis, the agency’s investigators can’t look into the infection further unless state authorities request their help. So far, Missouri hasn’t made such a request.
Add in the decision to no longer require hospitals to report hospital admissions over the summer for COVID, Flu, and other respiratory illnesses, and a lack of nationwide HPAI H5 wastewater testing, and we find ourselves making incredibly important decisions based on dangerously incomplete data.
But as long as our luck holds, we've nothing to worry about.
