bash - comment host file rows containing a string, if not already commented -

i attempting comment several entries in [/etc/hosts] file using sed. have following command works great:

 sed -i$(date +%s).bak '/devops/,/devops/s/^/# /' /etc/hosts 

my problem comes when re-run script containing above line, commented lines new comment. how can add ability skip commented [^#] rows?

thank you, lars

comment lines not commented:

sed -i$(date +%s).bak '/^[^#]*devops/s/^/# /' /etc/hosts