[palmer]

someone could be contagious but not show any symptoms

It's hard to produce a lot of viruses without showing some symptoms.

[CIB-173RDABN]

It’s hard to produce a lot of viruses without showing some symptoms.
—
I believe you are wrong.

Typhoid Mary never showed any symptoms but managed to infect people.

https://en.wikipedia.org/wiki/Mary_Mallon

see also

https://en.wikipedia.org/wiki/Asymptomatic_carrier