Mono is a viral infection that causes symptoms like fatigue, swollen glands, and a severe sore throat. It’s hard to say exactly how long someone with mono is contagious. Even researchers aren’t totally sure.

After you’re infected with Epstein-Barr (EBV) — the main virus that causes mono — the virus begins to shed in your throat. That means you can infect other people who come in contact with your saliva, so you have to be careful about kissing or sharing personal items like cups or utensils.

However, you may not realize you’re sick during this time. It can take four to six weeks from when you’re first infected for symptoms like fatigue, a sore throat, and muscle aches to appear. This is called the incubation period.

Once your symptoms do appear, they may last for two to four weeks.

You can pass the virus to other people through your saliva for up to three months after your symptoms subside. Some studies have reported that you may still be contagious for up to 18 months.

EBV spreads from person to person through saliva and other bodily fluids. This is why mono is often called the “kissing disease.”

If you kiss a person who has the virus — or you share personal items like utensils, glasses, food, or lip balm — you can become infected. You can also catch mono if someone who is sick coughs or sneezes close to you.

Teens and young adults are most likely to get sick with mono symptoms.

To avoid getting mono yourself, follow these tips:

  • Avoid close contact with anyone that you know is infected.
  • Don’t kiss or share personal items like toothbrushes, utensils, food, straws, or glasses with anyone that you suspect has mono.
  • Keep yourself healthy. Eat a nutritious diet, exercise daily, and sleep for at least six to eight hours nightly.
  • Wash your hands regularly.

To avoid spreading the virus if you’ve been infected, follow these tips:

  • Stay home and rest until your symptoms improve.
  • Don’t kiss or share any personal items — including utensils, glasses, lipstick, and food — with other people.
  • Ask your doctor if you should use a condom when you have sex and for how long. EBV can spread through semen during sexual contact.
  • Wash your hands regularly.

If you’ve caught mono, you typically have symptoms like:

  • fatigue
  • a sore throat
  • fever
  • swollen lymph nodes in your neck
  • headache
  • muscle aches

If your symptoms worsen or persist for more than a day or two, make an appointment to see your doctor. They can determine what’s causing your symptoms and advise you on any next steps.