Infectious Diseases Mononucleosis How Long Fatigue Lasts in Infectious Mononucleosis By Brandon Peters, MD facebook twitter Brandon Peters, MD, is a board-certified neurologist and sleep medicine specialist. Learn about our editorial process Brandon Peters, MD Medically reviewed by Medically reviewed by Richard N. Fogoros, MD on July 31, 2016 facebook linkedin Richard N. Fogoros, MD, is a retired professor of medicine and board-certified internal medicine physician and cardiologist. Learn about our Medical Review Board Richard N. Fogoros, MD Updated on June 09, 2020 Print Infectious mononucleosis (or mono) is a common contagious disease that may result in symptoms of profound fatigue or tiredness. If your fatigue doesn't go away, you might wonder if it has another cause, or whether you have chronic fatigue syndrome. Mono may be the sole cause or a contributor of persistent fatigue, but your doctor may also want to consider sleep disorders such as sleep apnea if you're not getting better. Paul Bradbury / Getty Images Mononucleosis Causes Mononucleosis is not a sleep disorder but it can cause fatigue that's just as debilitating as a sleep disorder. Mono is sometimes called the "kissing disease" due to its easy transmission via saliva, which means a lot of people catch it via a kiss or by personal contact, as well as sharing of food and dishes. The condition is characterized by: FeverInfection of the tonsils or throatSwelling of lymph nodes. Most cases of mono are caused by the Epstein-Barr virus (EBV), which is quite common, eventually infecting between 90% and 95% of all adults. (However, most people experience no symptoms of EBV.) This virus is spread by personal contact. Mono can also be caused by cytomegalovirus (CMV). Mono infections are very common among teenagers and young adults, especially those living in close quarters, like in dormitories on college campuses. When Fatigue Doesn't Improve For most people, the symptoms of fatigue associated with mono will gradually resolve over a period of two weeks to a few months. In a minority of people, though, the fatigue may still be present six months after the initial infection. In those cases, further evaluation may be necessary. If fatigue persists beyond six months, your doctor may start to consider a diagnosis of chronic fatigue syndrome, as EBV is theorized to be a possible cause of this disease. Though the relationship isn't fully understood, it may represent long-standing impacts of the initial infection. It may also be important to look at sleep disorders that can cause sleepiness and fatigue, including obstructive sleep apnea and insomnia. These extremely common conditions often contribute to unrestful sleep. Because they require different treatment, they shouldn't be overlooked as having a possible role in ongoing symptoms. Depending on your specific symptoms, your doctor may also test you for anemia and thyroid dysfunction. Depression and anxiety are also common causes of fatigue. Mononucleosis Doctor Discussion Guide Get our printable guide for your next doctor's appointment to help you ask the right questions. Download PDF Email the Guide Send to yourself or a loved one. Sign Up This Doctor Discussion Guide has been sent to {{form.email}}. There was an error. Please try again. A Word From Verywell If you are struggling with debilitating fatigue or tiredness, talk to your doctor about it and see what tests they recommend. Because fatigue has numerous possible causes, the diagnostic process can be long and frustrating. Remember that the end goal is identifying the cause of your fatigue so you can get the right treatment and get your life back on track. That's worth the wait. Was this page helpful? Thanks for your feedback! Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life. Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit Article Sources Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Centers for Disease Control and Prevention (CDC). Epstein-Barr Virus and Infectious Mononucleosis. May 8, 2018. Australian Academy of Science. Kissing the Epstein-Barr virus goodbye? Updated June 24, 2015. ScienceDaily. Epstein-Barr: Scientists decode secrets of a very common virus that can cause cancer. Published December 15, 2010. Centers for Disease Control and Prevention. Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Possible Causes. Reviewed March 19, 2019. Additional Reading Macsween KF, Higgins CD, McAulay KA, et al. Infectious mononucleosis in university students in the United Kingdom: evaluation of the clinical features and consequences of the disease. Clin Infect Dis. 2010;50(5):699-706. doi:10.1086/650456