Can You Get Mono Twice?

Childhood Infection Basics

A mother checking her son's lymph glands.
Swollen lymph glands are a classic sign of mono. Getty Images

Question. Can you get mono more than once?​

Answer. Although technically you should get infectious mononucleosis, or mono, only once in your life, there are some scenarios in which someone could get mono again.

Benefits of Natural Infections

One of the few benefits of getting a natural infection, whether it is mono, chicken pox, or measles, etc., is that you typically develop natural immunity and shouldn't get the same infection again.

Of course, this doesn't work for all infections. That's why you can get the flu, RSV, strep, and many other infections multiple times.

It usually does work for mono though.

Most people just get mono once.

Is It Really Mono Again?

One reason that a child might be diagnosed with mono a second time is that they were previously misdiagnosed. The monospot test for mono can give false positive results (the test is positive even when your child really doesn't have mono) up to 10 percent of the time. So a child could have had mono symptoms and a positive monospot, but their infection could have been caused by another virus, unless the results were confirmed by positive Epstein-Barr virus titers (which isn't always done or necessary).

Also, some children are given a simple clinical diagnosis of mono, without any testing, so you can't be sure that they had mono in the first place. Or they may have been diagnosed with mono after only having a suspicious complete blood count, which is not specific for EBV and mono.

It is also possibly that a child really did have mono in the past, but has been misdiagnosed on the second go round. Once you have mono, your Epstein-Barr virus titers stay postive for years and some stay positive for the rest of your life. It is easy to misinterpret these titers and think that a long past mono infection was very recent or that their mono has been reactivated.

You may not have even known that your child had mono in the past. It is actually not uncommon to test a teen for mono and discover that they are already immune, meaning that they had it when they were younger. This makes more sense when you understand that mono symptoms are often milder when you are younger. In fact, about half of children in developed countries get mono before they turn five years old and many of these children don't have any symptoms at all.

Mono Symptoms vs Mono

You could also have a different virus causing mono-like symptoms.

Although the Epstein-Barr virus (EBV) is usually thought of as the official cause of mono, and you should only get EBV infections once, many other viruses can cause similar mono-like illness, including CMV, adenovirus, Toxoplasma gondii, HIV, rubella, hepatitis A, human herpesvirus-6, and human herpesvirus-8.

So even after having mono, your child could later get a mono-like illness with the same symptoms as mono, including fever, sore throat, and swollen glands, that is caused by another virus.

What To Know About Getting Mono A Second Time

While the 'right' answer may be, 'No, you can't get mono caused by EBV more than once,' your child can have mono symptoms and might even be diagnosed with mono more than once in his life.

The Epstein–Barr virus is a type of herpesvirus though and like other viruses of this family, including herpes and chicken pox, EBV can remain latent in your body after an infection. Although it doesn't typically reactivate itself like herpes (recurrent cold sores) or chicken pox (shingles), it can cause a problem if you later develop a problem with your immune system and basically lose your immunity to your past infection.

Sources:

Behrman: Nelson Textbook of Pediatrics, 17th ed.

Long. Principles and Practice of Pediatric Infectious Diseases (Fourth Edition) 2012

Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases (Eighth Edition), Volume 2, 2015

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