Infectious mononucleosis is most likely to cause noticeable illness in teenagers and young adults, especially college-age people. It is usually caused by the Epstein-Barr virus (EBV), which many people catch during childhood without clear symptoms. When someone first gets EBV as a teen or young adult, they are more likely to develop the familiar illness. People of any age can develop it, however.
Which age groups are most likely to get mono?
Infectious mononucleosis, often called mono, is most common in teenagers and young adults. The National Health Service (NHS) identifies people aged 15 to 24 as the age group most commonly affected by glandular fever, another name for mono. College students are also a commonly affected group.
According to the Centers for Disease Control and Prevention (CDC), at least one in four teenagers and young adults who become infected with EBV develop infectious mononucleosis. This helps explain why the illness is frequently discussed in connection with high school, college, and early adulthood.
Why are teenagers and young adults more likely to develop mono?
The main reason is the difference between catching EBV and developing noticeable symptoms. Most people become infected with EBV at some point in their lives. However, the age at which the first infection occurs can influence how the illness appears.
The CDC's information on Epstein-Barr virus explains that EBV infections in childhood usually cause no symptoms or symptoms that resemble a brief, mild childhood illness. When the first infection occurs during adolescence or young adulthood, the person is more likely to experience the typical symptoms associated with mono.
These symptoms may include unusual tiredness, fever, a sore throat, and swollen lymph nodes, particularly in the neck. Some people also develop swollen tonsils. These experiences can occur with other illnesses, so age alone cannot establish whether someone has mono.
Are children less likely to get infectious mononucleosis?
Children can become infected with EBV, but they are less likely than teenagers and young adults to develop the classic illness. Many children have no obvious symptoms, while others experience symptoms that can be difficult to distinguish from common childhood infections.
As a result, a child may have an EBV infection without anyone realizing that the virus is responsible. The virus can still be present in the population and spread through saliva. The MedlinePlus infectious mononucleosis information explains that children often have no noticeable symptoms, whereas teenagers and young adults are more likely to experience the typical features of mono.
What increases the chance of exposure to the virus?
Age is the clearest population-level pattern, but exposure also matters. EBV spreads mainly through saliva, and people can carry the virus without knowing they have it. Certain everyday activities can create opportunities for saliva to pass from one person to another.
- Kissing: Direct contact with the saliva of someone carrying EBV can spread the virus.
- Sharing drinks or food: Drinking from the same cup or sharing food can expose someone to infected saliva.
- Sharing items that touch the mouth: Items such as toothbrushes, eating utensils, and lip balm can provide another route of exposure.
- Close social contact involving saliva: People who frequently share drinks or other mouth-contact items may have more opportunities for exposure.
The World Health Organization (WHO) identifies saliva as the main route of transmission and explains that people may spread EBV even when they do not know they are infected. These activities increase opportunities for exposure, but they do not mean that infection or symptomatic mono will necessarily follow.
Can adults over 25 get infectious mononucleosis?
Yes. Infectious mononucleosis can occur at any age, including in adults over 25. The condition is simply less commonly recognized in older adults than in teenagers and young adults. An adult who has not previously been infected with EBV can develop mono after a first infection.
Because EBV is widespread, many adults have already encountered the virus by the time they reach middle age. The CDC's EBV guidance notes that most people become infected during their lifetime, often during childhood. Having an EBV infection in the past does not mean that a person will have experienced mono, and it is important to distinguish past exposure from a new illness.
Does a weakened immune system affect the risk?
Immune status can matter in a different way from age. After the initial EBV infection, the virus remains inactive in the body and can sometimes reactivate. According to the CDC, people with weakened immune systems are more likely to develop symptoms when this reactivation occurs.
This does not mean that every person with a weakened immune system will develop infectious mononucleosis. Their risk and the nature of any illness depend on their individual circumstances. A healthcare professional can assess unusual or persistent symptoms in the context of a person's medical history and immune status.
What should you know if you may have been exposed?
Being a teenager or young adult, attending college, or knowing someone with mono does not establish that you have the infection. Exposure does not always lead to noticeable illness, and EBV can spread from people who do not have obvious symptoms.
When symptoms occur, they may include unusual fatigue, fever, sore throat, and swollen lymph nodes. These symptoms can overlap with other infections. If you experience persistent or worsening symptoms, significant difficulty swallowing, or fatigue that disrupts daily activities, seek medical evaluation. A healthcare professional can review your symptoms, medical history, and examination findings and decide whether testing is appropriate.
The most important distinction is that teenagers and young adults are the group most likely to experience recognizable mono after a first EBV infection, while EBV itself is common across age groups. Understanding this difference helps explain why mono is associated with young adulthood without suggesting that age or exposure alone determines an individual's health.