Mononucleosis (mono) is a viral infection that causes a sore throat and fever.
Cases often happen in teens and young adults. It goes away on its own after a few
weeks of rest.
What Causes Mono?
Mononucleosis (mah-no-noo-klee-OH-sus), or infectious mononucleosis,
usually is caused by the Epstein-Barr virus
(EBV). Most kids are exposed to EBV at some point while growing up. Infants and young
kids infected with EBV usually have very mild symptoms or none at all. But infected
teens and young adults often develop the symptoms that define mono.
Other viruses, such as cytomegalovirus,
can sometimes cause a mono-like illness too.
What Are the Signs & Symptoms of Mononucleosis?
Signs of mono usually show up about 1–2 months after someone is infected
with the virus. Its most common symptoms are sometimes mistaken for strep throat or
the flu. These include:
belly pain with a larger-than-normal liver or spleen (an
organ in the upper left part of the belly)
loss of appetite
Is Mono Contagious?
Mono is contagious. It spreads from person to person through contact with saliva
(spit). It's nicknamed "the kissing disease" because it
can spread through kissing. It also spreads through coughing and sneezing, or when
people share something with spit on it (like a straw, drinking glass, eating utensil,
Mono can also spread through sexual intercourse and blood transfusions, but this
is much less common.
People who've been infected carry the virus for life, even after symptoms stop
and even if they had no symptoms. The virus is then "dormant," or inactive. Sometimes
the dormant virus "wakes up" and finds its way into a person's saliva. This means
that they can be contagious from time to time, even when they have no symptoms.
How Is Mono Diagnosed?
To diagnose mono, doctors do an exam to check for things like swollen tonsils and
an enlarged liver or spleen, common signs of the infection. Sometimes the doctor will
do a blood test.
How Is Mono Treated?
The best treatment for mono is plenty of rest and fluids, especially early in the
illness when symptoms are most severe. There is no specific medicine for mono, but
acetaminophen or ibuprofen
can help to relieve fever and aching muscles. Antibiotics
will not help, because they're only effective against bacteria. Someone with mono
who takes an antibiotic often ends up getting a rash.
Never give aspirin to a child who has a viral illness because its use has been
linked to Reye syndrome, which may
cause liver failure or even be fatal.
How Long Does Mono Last?
Mono symptoms usually go away within 2 to 4 weeks. In some teens, though, the tiredness
and weakness can last for months.
Can Mono Be Prevented?
There is no vaccine to protect against the Epstein-Barr virus. But you can help
protect your kids from mono by making sure that they avoid close contact with anyone
who has it.
Many people who have mono won't have symptoms, but they can still pass it to others.
So kids should wash their hands
well and often, and not share drinks or eating utensils with others, even people who
What Else Should I Know?
Mono can make the spleen swell for a few weeks or longer. An enlarged spleen can
rupture, causing pain and bleeding inside the belly, and needs emergency surgery.
So doctors recommend that kids who have mono avoid contact sports for at least a month
after symptoms are gone. Your child should stay away from rough play, heavy lifting,
and any strenuous activities until the doctor says it's OK.
In most cases, mono symptoms go away in a matter of weeks with plenty of rest and
fluids. If they seem to linger or get worse, or if you have any other questions, call