Final answer:
Viruses that cause infections with periods of activity and dormancy are called latent viruses. Latent viruses may exist in a dormant state within the host's cells without causing symptoms until they reactivate.
Step-by-step explanation:
Viruses that cause infection resulting in alternating periods of activity with symptoms and inactivity without symptoms are called latent viruses. These viruses can enter a state of dormancy inside the host cell, known as latency, and may initially cause an acute infection before becoming dormant. Examples of latent viruses include herpes simplex viruses, which cause herpes in humans, and the varicella-zoster virus that causes chickenpox and shingles.
In contrast to chronic infections, latent infections involve the pathogen going dormant for extended periods with no active replication. Patients might not exhibit any signs of disease during these dormant periods and might be unaware they are carriers unless tested. Some viruses, such as human herpesviruses, are capable of asymptomatic infection, successfully infecting hosts without causing noticeable symptoms.