I do know some flu strains (typically the milder ones) tend to go for receptors in the Upper Respiratory Tract, and some of the typically nastier strains like H5N1 tend to go for receptors deep in the lungs. Is this what is happening with Omicron vs. Delta?
What has me puzzled is that Delta is described as generating exceedingly high viral loads in nasal passages: All seem to agree that's why it was much more infectious than earlier variants. Spreaders had mild head cold symptoms if any at all, and yet were able to chuck out astonishing virion quantities to those exposed to the spreader(s). I assumed this would happen B4 the infection progressed further in the spreader (lungs, bloodstream) making the occasional spreader / victim sick enough to go to the ER or be hospitalized. The "sick" with Delta ("sick" = your description - I'm not sure if that means seriously ill or hospitalized?) would only be a small fraction of those infected with Delta, unless they were hospitalized for something else. Only for purposes of discussion, I'll ballpark it at 10%. Nonetheless, if 10% of the Delta cases are "sick", that leaves 90% "mild or asymptomatic" by your description, some of whom one would expect to be in for other reasons, much as the Omicron cases. I am confused as to "where are they?"
The only explanations that make sense to me go back to previous discussions I had with BeauBo in which I concluded Delta is a sort of 2-stage disease: This from BeauBo's description of, in certain individuals, Delta moving on in from the upper respiratory tract to the lower respiratory tract and the bloodstream. OR, perhaps we have with Delta a situation where in approx. "10%" of the cases (contrived figure from above) Delta attacks the lower respiratory tract more directly(?), somewhat like H5N1, but in most cases attacks primarily the upper respiratory tract and would then be clinically indistinguishable from the even greater number of Omicron cases.
Personally, I think it's sequential, with some URI's progressing to LRI's, but, either way...
This would lead to me describing your cases in 2 groups: Group 1 = "Delta L" (the two LRI's.) Group 2 = Omicron + "Delta U" (the ~ 50 URI's). But, without sequencing or some other variant detecting test, Omicron vs. Delta U would be VERY difficult to differentiate. No?
OTOH, I suppose another consideration is that Delta L takes longer to develop, and the two "sick" cases you saw may therefor be Delta stragglers. So, new Delta infections might well be down to near zero, with all the Delta U cases pretty much having already run their course?
Haha - completely OT, but I was about to use the word “pernicious” in my long post, then decided against as the definitions vary too much. One in particular (Google search) cracked me up:
per·ni·cious
/pərˈniSHəs/
adjective
having a harmful effect, especially in a gradual or subtle way.
“the pernicious influences of the mass media”
Whoa! WHO snuck that one in??!!
Both Delta and Omicron replicate very rapidly in the Nasal mucosa/upper respiratory tract, as compared to the earlier strains.
However, Delta is much more able to get down into the lung tissues than is Omicron - ten times as much, or better.