There are many sub-types of the herpes virus, which are responsible for a spectrum of diseases. Types 1 and 2 are the Herpes Simplex Virus (HSV).

HSV 1 is typically known to cause oropharyngeal herpes or herpes stomatitis, and HSV 2 causes genital herpes, but either of these two viruses can appear in the oropharyngeal or genital regions.

Infections with HSV are transmitted through contact with lesions, mucosal surfaces, genital secretions, or oral secretions. HSV-1 and HSV-2 can also be shed from skin that looks normal and has no sores or blisters. Generally, a person can acquire HSV-2 infection only through sexual contact with someone who has a genital HSV-2 infection.

Transmission of HSV most commonly occurs from an infected partner who does NOT have symptoms of an actual herpetic infection such as a visible sore and may not be aware that he/she is infected. In persons with asymptomatic HSV-2 infections, genital HSV shedding occurs on 10% of days, and on most of those days the person has no signs or symptoms.

So in a nutshell, the answer to your question is YES, herpes can be transmitted outside periods of outbreaks and visible blisters.