How long is infectious mononucleosis (Mono) contagious?

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Last updated: May 21, 2025View editorial policy

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From the Research

Mononucleosis is most contagious during the acute phase of illness, typically for about 4-8 weeks after symptoms begin, as stated in the most recent study 1. The virus that causes mono, Epstein-Barr virus (EBV), can be shed in saliva for months or even years after the initial infection, even when a person feels completely well. The highest risk of transmission occurs during the period when symptoms like fever, sore throat, and fatigue are present. The virus spreads primarily through saliva, which is why mono is sometimes called the "kissing disease," though it can also spread through sharing drinks, food, or personal items. Some key points to consider include:

  • The best approach to prevent spreading mono is to avoid kissing or sharing personal items while symptomatic, practice good hand hygiene, and cover coughs and sneezes 1.
  • There is no specific medication that eliminates the contagious period, as antiviral medications are not typically effective against EBV 2.
  • The virus remains dormant in the body after infection, and occasional viral shedding can occur throughout life, though the risk of transmission decreases significantly after the acute illness resolves 3.
  • Current guidelines recommend that patients with infectious mononucleosis not participate in athletic activity for three weeks from onset of symptoms, and shared decision-making should be used to determine the timing of return to activity 1. It's essential to prioritize supportive care and avoid unnecessary treatments to minimize complications, as stated in 2 and 1.

References

Research

Infectious Mononucleosis: Rapid Evidence Review.

American family physician, 2023

Research

Infectious Mononucleosis: An Updated Review.

Current pediatric reviews, 2024

Research

Infectious Mononucleosis.

Current topics in microbiology and immunology, 2015

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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