There is a lot of uncertainty, doubt, and imprecision in those statements. "Some spread might...", "might be possible...", "this is not thought...", etc. These really mean: yes, it's possible.

I would say asymptomatic carriers are the biggest concern.

There's a big difference between 'yes, is technically possible' to having proof (and therefore certainty) that this is a big factor and a differentiator from other from other viruses.

I think the proof is out there: https://www.infectioncontroltoday.com/covid-19/asymptomatic-...

Thank you for the links. I found it before as well with some quick googling but I felt the title deceptive after reading the actual studies linked [0] [1].

>>> The sequence of events suggests that the coronavirus may have been transmitted by the asymptomatic carrier.

>>> If the findings in this report of presumed transmission by an asymptomatic carrier are replicated, the prevention of COVID-19 infection would prove challenging. The mechanism by which asymptomatic carriers could acquire and transmit the coronavirus that causes COVID-19 requires further study.

>>> Considering the reported similarity in viral loads between asymptomatic and symptomatic patients [14] and that transmission of SARS-CoV-2 by asymptomatic or paucisymptomatic cases may be possible, even though there is no clear evidence as yet of asymptomatic transmission, the relatively high proportion of asymptomatic infections could have public health implications

No clear evidence of asymptomatic transmission. A lot of 'probably', 'suggests' as before. It's certainly a growing possibility, but not I'd not call it proven yet as a big factor.

[0] https://www.eurosurveillance.org/content/10.2807/1560-7917.E...

[1] https://jamanetwork.com/journals/jama/article-abstract/27620...

There are people getting sick without having been in contact with other people who are sick. How else would that happen?

"Most contagious when symptomatic" is not even remotely the same thing as "not contagious unless symptomatic". We also don't have a good picture of what symptoms look like aside from the most serious cases.

How would you possibly know reliably they were not in contact with anyone sick?, particularly when being in contact means touching any surfaces where the virus landed hours or it seems even days ago