Thank you for your query at DoctorSpring.com
I understand your concern.
Just for a little more clarity, you are referring to fever blisters/ cold sores ( HSV 1 infection ) right?
Yes they are highly contagious and even in the absence of any active lesion, it can be spread to other people via oral secretions. However the incidence of this mode of transmission is low.
Where exactly did you kiss the baby?
Feel free to discuss further queries,