There are many different types of herpes viruses and they all have different effects. A common one is the herpes simplex virus that causes cold sores. But there are also other herpes viruses that can, for example, cause shingles and glandular fever.
Herpes viruses may be present in the body but dormant. That means they’ll only become active if your immune system is weakened, for example if you become stressed. Untreated HIV can also weaken the immune system, so if you do have HIV, it’s advisable to stay on HIV treatment.