The way mono works in the body is tricky, so lots of people are confused about
how long it is contagious. If you get mono, the virus stays
in your body for life. That doesn't mean that you're always
. But the virus can surface from time to time and risk infecting someone
Here's how it works:
Mono, or mononucleosis,
usually is caused by an infection with the Epstein-Barr virus (EBV).
People who have mono can be contagious from the time they first become infected.
But they may not know that they have the virus. It takes a while for mono symptoms
(like tiredness, fever, muscle aches, headache, or sore throat) to show up — about
1–2 months, in fact. This is called the incubation period.
To make things even more confusing, some people can carry the virus without ever
getting any mono symptoms. So they may not know they have been infected, but they
can still pass it to others. In fact, most people have been infected with EBV by the
time they reach adulthood.
People are definitely contagious while they have symptoms, which can last 2–4 weeks
or even longer. Health experts aren't sure how long people with mono stay contagious
after symptoms are gone, but it seems they can spread the infection for months after
that. Then, the virus stays dormant (inactive) in the body for the rest of a person's
Sometimes the dormant virus can "wake up" and find its way into a person's
saliva (spit). That person might not feel ill or show any mono symptoms, but can spread
the virus to other people. So there's a very small chance that people who have had
mono in the past can pass it to others, even when they feel OK.
The bottom line is that it's hard to prevent mono from spreading.
Because EBV is so sneaky, infections are common. That's why doctors urge everyone
to wash their hands
well and often. It's the best way to keep germs at bay.