How long can herpes go undetected?

The amount of time that herpes can go undetected can vary from person to person. In some cases, herpes may not cause any symptoms and may go undetected for years. In other cases, herpes may cause symptoms that are mistaken for other conditions, such as the common cold or flu. In general, herpes is most contagious during the first few days after an outbreak, but it can also be transmitted before and after symptoms appear.