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How Long is Mono Contagious?


Updated May 16, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Question: How Long is Mono Contagious?

Mononucleosis (Mono), also known as "the kissing disease," is caused by the Epstein-Barr virus (EBV). It is mainly spread through saliva. While infants are breastfeeding, they are protected from an EBV infection. After children are no longer receiving antibodies through their mother's breast milk, exposure to EBV can cause a mild illness that may be similar to many other childhood illnesses. Once your child has matured into adolescence or becomes a young adult, infection with EBV will cause infectious mononucleosis approximately 35 to 50 percent of the time.

Symptoms of mono range in severity from person to person, but usually include extreme fatigue and an extremely sore throat. For a more complete listing of symptoms please refer to Symptoms of Mono. Your doctor will most likely ask that you take a leave of absence from school or work so that you can rest up and get better, as antibiotics will not help you get over a viral infection.

How Long Is Mono Contagious?

At this point in time, there is not a confirmed answer as to how long a person with an acute (current) infection of mono remains contagious. Complicating this question, is the fact that once having mono, EBV remains in your body for the rest of your life. EBV usually remains in the body in a dormant, sleeping state. However, there is the chance that your dormant EBV infection will reactivate. A reactivated EBV infection may or may not be accompanied by symptoms.

Some research shows that even in the late stages of a mono infection, a high number of EBV remains in the saliva. A study published in The Journal of Infectious Diseases showed that after acquiring infectious mononucleosis, you may be infectious for greater than six months. You should start feeling better within one to two weeks and most people will have resolution of their symptoms well before six months. In rare cases, fatigue may still be felt by some people after an acute case of infectious mononucleosis (see Mono and Fatigue).

What Should I Avoid Doing While I Am Contagious?

It's hard to prevent the spread of mono because EBV is actually present in the majority of the population (95 percent of people between the ages of 35 and 40 are positive for EBV). However, while you are having symptoms and until you are fully recovered, there are some basic things that can help you from spreading it to others who have not had a prior exposure to the virus:
  • Avoid kissing
  • Do not share eating utensils with others
  • Do not drink from the same glass as others

There is some research suggesting that sexual intercourse may be a possible risk factor for acquiring EBV, but that is not known for certain. One thing to remember is that despite feeling better, you may be contagious and may not know when your dormant infection may reactivate. It is important to be cautious, but realize that, unlike a cold or the flu, you cannot always prevent this infection from spreading.


Centers for Disease Control and Prevention. 2006. Epstein-Barr Virus and Infectious Mononucleosis. Accessed: August 21, 2011 from http://www.cdc.gov/ncidod/diseases/ebv.htm

Fafi-Kremer S, Morand P, Brion JP, Pavese P, Baccard M, Germi R, Genoulaz O, Nicod S, Jolivet M, Ruigrok RW, Stahl JP, Seigneurin JM. 2005. Long-term shedding of infectious epstein-barr virus after infectious mononucleosis. The Journal of Infectious Disease 191 (6): 985-989. Accessed: August 21, 2011 from http://jid.oxfordjournals.org/content/191/6/985.full.pdf+html

Uptodate. 2011. Patient information: infectious mononucleosis (mono) in adults and adolescents. Accessed: August 21, 2011 from http://www.uptodate.com/contents/patient-information-infectious-mononucleosis-mono-in-adults-and-adolescents

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