Top ten things you didn’t know about mono. And kittens. (You won’t believe what happens next!)

The Pediatric Insider

© 2015 Roy Benaroch, MD

So I noticed that blog posts cast as questions and answers, or “top ten lists”, seem to get a lot of hits. It also seems to help to include gratuitous references to high school, and pictures of kittens. And pleas to share with friends, and vague connections to charity. So let’s give it a try! If you love kittens and sunshine, be sure to share this with every human on the planet! For every share, some kind of charity will get loads of money. Probably.

Thanks to Kristi for the mono questions.


1. What’s mono?

“Mono” is short for “infectious mononucleosis”, a common viral infection of childhood. The “monocytosis” refers to what the blood smear looks like under a microscope– there are often a lot of white cells called “monocytes.”

Kids with mono have a wide range of illness. Some, especially younger children, are barely sick– maybe with a bit of sore throat and fever. Teenagers often fare worse, sometimes with a severe sore throat, swollen lymph nodes, fevers, and very low energy that can linger for weeks. And some people have active mono, spreading virus, with no symptoms at all.


2. What causes mono?

Classic mono is usually caused by a virus called “Epstein Barr” (often abbreviated EBV). A very similar illness can be caused by other viruses (CMV, or acute HIV), or other infections (toxoplasmosis.)


3. Is it true that you can only get it from kissing?

Well, maybe not only. During mono illness the saliva is loaded with mono virus, so sharing spit is the best way to give it to a friend or loved one. Mono can also spread by sharing utensils or cups, but the most efficient way to share saliva is kissing. Especially when standing upright in a high school hallway. So watch out!

Mono does not spread through casual or household contact.


4. How long is mono contagious?

It’s likely that people are most contagious when they feel the sickest with fever– but at least some people will continue to shed EBV in their saliva for many months, maybe even a year or two. And yes, they’re contagious that whole time. Did I mention kissing in the hallway wasn’t a great idea?


5. How long is the incubation period? I mean, how long does it take to get sick?

The incubation period varies. It’s probably in the range of 30-90 days. So when a teenager comes down with mono, it’s just about impossible to figure out who they caught it from.


6. What’s up with the spleen thing? I don’t even know what a spleen is!

IKR! I thought a spleen was a word Shakespeare used to confuse people:

“Saint George / Inspire us with the spleen of fiery dragons!”

“Haply my presence / May well abate the over-merry spleen”

But it turns out the spleen is an organ at the top left of your abdomen, usually tucked up under your ribs there. In about 40-50% of teenagers with mono, the spleen will get enlarged.

The problem, though, isn’t just that the spleen is large– it’s that rarely the spleen can rupture. And that’s really bad. A spleen rupture can occur even without mono, usually from trauma (like a car accident.) It’s thought that the enlarged spleen that can occur during mono might increase the risk of rupture, especially during tackle or rough sports (though that’s not entirely proven.) It’s also not clear if children with non-enlarged spleens are at risk for rupture during mono, or how long the risk lasts. Some people restrict everyone with mono from rough or tackle sports, regardless of spleen size; others use an ultrasound to measure spleen size (though that’s never been shown to help prevent rupture.) Should kids sit out for a fixed number of weeks, or until the spleen size returns to normal? There is no consensus on this issue. Spleen rupture itself is really quite rare, so it’s hard to do a study of the best way to prevent it.


7. Is it true that you can only get mono once?

Yes, or at least usually. Mono caused by EBV will only happen once in most people, even though the virus itself lurks in your body afterwards. Mono-like symptoms can rarely recur at times of immune compromise. The EBV virus can resurface to cause other health problems if the immune system is really knocked out (during chemotherapy, say, or with advanced HIV infection.)

It’s also possible that other infections trigger mono-like symptoms in some people after EBV infection.


8. Wait a minute. I’ve been tested for mono a bunch of times, and I’ve been told I had it more than once. What’s the deal?

It turns out that there are bunch of different tests for mono. Some show “past infections” that may have occurred years ago. Because you “test positive” for mono, that doesn’t mean you have acute mono right now. It might just mean you got over mono years and years ago. It depends on the test.


9. How is mono treated?

Rest, rest, rest. Fever reducing medicine can help if fevers are making you feel bad (though the fever itself won’t hurt you.) Extra fluids, pain medicine for the sore throat, and sleep.

Rarely, steroids are used. This can help especially if the swollen glands in the throat are making it hard to drink or talk or breathe.

Fully resting at the worst part of the illness seems to help prevent mono from turning into weeks or months of malaise and low energy. However, you don’t want to rest and miss school too long– once you’re starting to feel better, try to make it back to school at least part days, and work up from there. Though rest is important, too much rest for too long leads to deconditioning and social isolation, which can make it hard to return to full activities. Teens with more-severe mono sometimes need an individualized treatment plan with a roadmap to get them recovered and back to school.


10. Did you pad this out to ten questions?


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2 Comments on “Top ten things you didn’t know about mono. And kittens. (You won’t believe what happens next!)”

  1. Dr.M Says:

    Love the kittens!


  2. Bryce Williams Says:

    I like the kittens also


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