While most people who have mononucleosis only display the symptoms once, they carry the virus the rest of their lives, and symptoms cam reappear later in life in rare instances, according to Mayo Clinic. Additionally, it is possible for the person to become contagious again without displaying any symptoms after they heal from the initial infection. In these cases, the Epstein-Barr virus becomes detectable in the saliva.
Mononucleosis has an incubation period of four to seven weeks before the symptoms become evident. However, the person can be contagious from the time of infection, warns KidsHealth. The symptoms, including sore throat and extreme tiredness, last from two to four weeks. After the symptoms subside, the person remains contagious for many months, with some research suggesting as long as 18 months. After the contagious period, the virus normally becomes dormant.
Patients who have had mono in the past and begin experiencing similar symptoms again should contact their doctor, advises Mayo Clinic. The doctor can diagnose the cause of the symptoms. Diseases such as toxoplasmosis and hepatitis have similar symptoms to mono.
Mononucleosis spreads through the saliva, according to KidsHealth. While some people refer to it as the kissing disease, it can also spread through sharing drinks, a toothbrush or eating utensils. Avoiding these actions, along with frequent hand washing, can lower the risk of catching the virus.