MOUNDS, Oklahoma - A Green Country hospital says it's seeing a high number of mono cases this season.

Mononucleosis is a highly contagious virus that can last weeks or even months.

Seven-year-old Trinity would rather be at school, but she stayed home Wednesday, playing games on her iPad.

Her mom, Lisa Cupps, said Trinity started throwing up around 11:00 Tuesday night and couldn't stop.

"Every five to 20 minutes from that point on, she's throwing up," she said.

Trinity got so sick, her mother said she couldn't eat or drink, and, she started dry-heaving.

Cupps said, "She couldn't keep Sprite down, she couldn't keep Pedialyte down, nothing. No fever, she wasn't talking about her throat hurting, nothing. But I was sitting there, going, 'OK, she's getting dehydrated, she can't even go pee now.'"

Trinity's father, Gary, took her to St. John Sapulpa's emergency room where a doctor told him Trinity has mononucleosis - and it's more widespread than you might think.

"He said that he's had a lot of more cases of this than the flu this season," Gary Cupps said.

Mono typically affects teens and young adults the most, but children can get it.

It's spread primarily through saliva. Symptoms usually include high fever, headache sore throat, and sometimes, like in Trinity’s case, vomiting.

The only real cure is rest.

Cupps said a school nurse advised her that as long as she feels better, Trinity can come back to school - but she won't be able to play on the playground for up to eight weeks because mono can make her spleen very sensitive.

Experts say those mono symptoms typically hit four to six weeks after you've already gotten the virus.

Lisa Cupps said, "This is worse than the flu. 'Cause this will get you and you don't even know you got it."