How Long Do Symptoms of Fatigue Last in Infectious Mononucleosis?

Infectious mononucleosis (or mono) is a common contagious disease that may result in symptoms of profound fatigue or tiredness, but how long does the fatigue typically last? What else might cause persisting fatigue? Is it due to chronic fatigue syndrome? Learn about how mono contributes to fatigue and what other conditions and sleep disorders like sleep apnea to consider if the fatigue is not getting better.

What Causes Mononucleosis or Mono?

Mononucleosis is not a sleep disorder per se, but because it is so common and the fatigue can be so debilitating, it is worth a closer look. It is sometimes called the "kissing disease" due to its easy transmission via saliva. Mono is characterized by fever, infection of the tonsils or throat, and the swelling of lymph nodes.

Mono is caused by the Epstein-Barr virus (EBV), which is quite common, eventually infecting 90 to 95 percent of all adults. 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.

People with mono often experience fatigue that may be persistent and severe. In a study of 150 patients, fatigue resolved slowly and was still present in 13 percent of people at six months. It appears to be more common and severe in women compared to men, especially among college students.

Severe Symptoms Associated With Mono

In very severe cases, mononucleosis may result in other neurologic symptoms affecting the nervous system. These can include meningitis and encephalitis, which are infections of the brain, or the tissues surrounding the brain and spinal cord called the meninges.

When present, this more severe infection might cause additional symptoms, including:

  • Confusion
  • Intense headache
  • Profound drowsiness
  • Coma

These complications occur very rarely. If present, additional medical attention may be necessary until the condition improves or resolves. This may result in a hospitalization lasting days to weeks.

What to Do If Fatigue Is Not Improving

In general, the symptoms of fatigue associated with mono will gradually resolve over a period of weeks to months. As noted, in a minority of people, the fatigue may still be present 6 months after the initial infection. In these individuals, further evaluation may be necessary.

If fatigue persists beyond six months, the condition called chronic fatigue syndrome may be entertained, as EBV has been considered as a possible cause of this disorder. Though not fully understood, it may represent long-standing impacts of the initial infection.

It may also be important to look at other sleep disorders that can cause sleepiness and fatigue, including obstructive sleep apnea and insomnia. These conditions frequently contribute to unrestful sleep and are extremely common. As they may be treated differently, they should not be overlooked as having a possible role in ongoing symptoms.

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A Word From Verywell

If you are struggling with debilitating fatigue or tiredness, speak with your doctor about the need for further evaluation, including routine testing for hypothyroidism, anemia, and sleep disorders. When necessary, a referral to a board-certified sleep physician may allow a sleep study to be performed to identify other contributors to unrefreshing sleep.

If sleep apnea is identified, treatment with continuous positive airway pressure (CPAP) therapy or oral appliance use may provide relief. There are also other effective treatments available for sleep disorders and these might help you to feel and function at your best. In rare cases, the use of stimulant medications may be necessary to resolve the persistent fatigue.

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Article Sources

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  • Rea, TD et al. "Prospective study of the natural history of infectious mononucleosis caused by Epstein-Barr virus." J Am Board Fam Pract. 2001;14(4):234-42.
  • Schellinger, PD et al. "Epstein-Barr virus meningoencephalitis with a lymphoma-like response in an immunocompetent host." Ann Neurol. 1999;45(5):659-62.
  • White, PD. "What Causes Prolonged Fatigue after Infectious Mononucleosis and Does It Tell Us Anything about Chronic Fatigue Syndrome?" J Infect Dis. 2007;196 (1):4-5.