library_construction_protocol: Biopsy specimens were collected in either HBSS + 10% FBS or Hibernate E Media +10% FBS, spun down, then digested using collagenase I, dispase and DNAse, papain, and trypsin. Cells were filtered through a 70 μm strainer, pelleted and washed, and then treated with an erythrocyte lysis buffer and washed again. The cells were then resuspended in PBS with 0.1% bovine serum albumin and 0.2% anti-clumping agent (Invitrogen) and immediately processed for scRNA-seq. Note that COVID PASC hyposmic patient 2 was split up into two different samples prior to loading on Chromium for single cell preparation (hence COVID_2_1 and COVID_2_2 notation) Samples were processed for scRNA-seq using Chromium Single Cell 3′ Paired-End, Dual-Index Library & Gel Bead Kit v3.1 (10X Genomics) targeting 10000 cells, then sequenced using NextSeq 150bp (Illumina) flow cells.