> However, the total number of COVID-19 cases is likely higher due to inherent difficulties in identifying and counting mild and asymptomatic cases.
> Nevertheless, all CFRs still need to be interpreted with caution and more research is required.
Like the cruise ships:
> The ministry has tested 4,061 people so far, of which 705 were positive, including 392 people who were asymptomatic.
So seems your estimate of "huge numbers of asymptomatic" is not far from the mark. Apologies. See also:
> Asymptomatic infection has been reported, but the majority of the relatively rare cases who are asymptomatic on the date of identification/report [due to contact testing] went on to develop disease. The proportion of truly asymptomatic infections is unclear but appears to be relatively rare and does not appear to be a major driver of transmission.
