For those of you that have asked me why I am convinced that cryptic lineages are coming from people, I can finally point to a pre-print with @dho and many fantastic collaborators in the UWisc and Wisc Public Health. medrxiv.org/cgi/content/sh…
It's pretty straightforward. We started with a sewershed that produces enough wastewater to fill about 30 olympic swimming pools a day. We sampled about a quarter cup.
But something didn't smell right.
It had a cryptic lineage, a SARS-CoV-2 RNA that was completely unknown.
For the next several months my collaborators continued to take sub-samples from throughout the sewershed and sent them to me to figure out which one 'didn't smell right'.
With each round of sampling we further narrowed the source of the cryptic lineage.
We finally narrowed the source to a single manhole, and then to a single set of bathrooms.
The sample from that bathroom contained by far the most SARS-CoV-2 RNA I had ever seen from a wastewater sample. We could have diluted it a million-fold and still detected the lineage.
This bathroom was not used by any rats or white tailed deer. The signal was coming from a person.
We also learned from this 'homogeneous sample' about the complete viral sequence. It was from a lineage that circulated over a year ago.
The person has been infected a long time.
We still don't know which person is the source (most were tested by nasal swabs and were negative), and more importantly, we don't know why the lineage is not spreading.
We suspect that the source is a long-term COVID infection of someone's GI tract.
There are still a lot of questions that need to be answered, but we have at least started to figure out what the right questions are.
• • •
Missing some Tweet in this thread? You can try to
force a refresh
This is weird. I was going through public wastewater sequences and found another BA.1.1 lineage that didn't get the memo that it is supposed to be extinct.
This time is was from Sioux City, Iowa (which is on the Nebraska border) in February. 1/
However, then I checked and realized that there were actually 3 BA.1.1 sequences deposited from Nebraska in the last month. They are very divergent, but closely related to each other, and they are from at least 2 different patients. 2/
I'm pretty sure the lineage from wastewater is the same sub-clade.
BA.1.1 has S:371L, but both the wastewater BA.1.1 and the patient sequences have S:371F.
Cryptic lineages desperately want to restore this glycosylation site (I've seen it restored 4 different ways), but the reversion is EXTREMELY rare in circulating lineages.
26/
Then there is the RBD. The cryptic lineages really want Q498H (the sequence in bats) or 498Y. As I mentioned, these changes are extremely rare in circulating lineages.
Seems this change probably has more to do with the tissue than with the species.
27/
Finally, the change in SC2 that messes up the s2m (29758T).
The s2m stem loop is a highly conserved RNA structure among some Corona, Astro, and Picorna viruses (which generally all infect the GI tract).
In this study we tracked the source of a SARS-CoV-2 cryptic lineage from the main treatment plant in a WI city all the way to a single set of bathrooms... using nothing but wastewater sampling and sequencing.
Back to curating the viruses we find from randomly sequencing the wastewater virome.
I've been a virologist for 30 years, how have I not heard of some of these viruses?
I don't think we knew about smacoviruses when I went to grad school.
Quail influenza? Who has pet quail and is flushing their waste? And please stop.
Could be a duck or chicken host, but still.
We have a program that compares the sequences to a viral database, but you kind of have to BLAST some of them individually to confirm what is real. H9N2 was real.