Two elementary parameters for quantifying viral infection and shedding
are viral load and whether samples yield a replicating virus isolate in cell
culture. We examined 25,381 German SARS-CoV-2 cases, including 6110 from
test centres attended by pre-symptomatic, asymptomatic, and
mildly-symptomatic (PAMS) subjects, 9519 who were hospitalised, and 1533
B.1.1.7 lineage infections. The youngest had mean log10
viral load 0.5 (or less) lower than older subjects and an estimated ~78% of
the peak cell culture replication probability, due in part to smaller swab
sizes and unlikely to be clinically relevant. Viral loads above
109 copies per swab were found in 8% of subjects,
one-third of whom were PAMS, with mean age 37.6. We estimate 4.3 days from
onset of shedding to peak viral load (8.1) and cell culture isolation
probability (0.75). B.1.1.7 subjects had mean log10
viral load 1.05 higher than non-B.1.1.7, with estimated cell culture
replication probability 2.6 times higher.