More on inactive H1N1 RNA in milk supply and wastewater sampling
Today's STAT article (May 8) compiled by Megan Molteni interviews several experts regarding earlier positive findings in both retail milk sampling and a Texas wastewater study
Those of you without a STAT subscription may want to consider signing up for a short period at least, since this source has been extremely active in digging up information on breaking information related to the H5N1 dairy issue and related influenza and potential pandemic response issues. I respect the publication prerogatives of the publishers and will not copy and paste information available only to subscribers and those trying out the free issue offers. Here is the article:
Bird flu in milk supply is likely coming from asymptomatic cows- STAT (statnews.com)
In reviewing the article, I think a few points need to be emphasized, with further comments from my experiences:
I agree with experts that non-clinically ill and/or recovered cows are likely shedding viral RNA which may or may not be infectious and can continue indefinitely. This occurs with other RNA viral infections in other species and makes declaring animals “negative” using cessation of PCR shedding a fool’s errand. The public must understand that residual PCR readings in milk are to be expected and are not hazardous with pasteurization of consumer products.
Milk processing plant locations will not perfectly match with state of dairy herd production. If an infected herd resides along a state line, milk could well be shipped to an adjoining state’s processing plant. If we begin to systematically test retail milk samples to measure infection incidence and genomic diversity in the national herd, we MUST NOT over-analyze the results to improperly assign state herd infection status based on bottling plant codes.
Even with sewage treatment processes working as designed, viral RNA (not live virus) may still survive the process and be detectable with sampling. Positive results do not necessarily indicate a failure in sewage treatment processes! If sampling is conducted in the sewage streams prior to treatment processes, chances of detection are likely greater.
While sewage sample readings may not indicate animal or human species of origin by itself, investigation of the variety of livestock upstream sewage sources will be useful. A dairy plant (as in TX) would indicate a likely dairy infection; a pork processing facility might signal a possible swine influenza infection. Secondary samples could be pulled closer to suspected sources to better differentiate possible etiologies for elevated readings.
When states are identified as having infected dairy cattle herds, wastewater surveillance in that state may not necessarily reflect increased H1N1 levels. Milk from infected herds may be processed out or state or in intrastate plants not connected to participating wastewater surveillance streams.
We must understand that indirect “fluids” sampling can only take us so far in mitigating this threat; however, it is a critical first step in developing some much-needed national incidence and widespread genomic surveillance data., albeit in an anonymous fashion. This data will fill in some basic knowledge gaps, and upcoming early research results will add to our understanding of disease processes in dairy animals and risk of further spillovers. With some uncertainty answered the industry may be more inclined to participate in more intensive on-farm studies and elimination projects based on much more certainty.
Over time I also expect that our public health colleagues will make progress in trust building with producers and their employees to allow more effective human surveillance and serologic testing.
I’ve been gratified by the tremendous interest in these posts. More information is flowing than I can cover. I hope you continue to find it useful.
We’ll get there!
John