In some cases, mononucleosis, or mono, can be a sexually transmitted infection (STI). However, this is not the most common way that it spreads. Usually, the cause is contact with saliva.

People who share eating utensils, toothbrushes, or drinking glasses could contract mono from a person who has the infection. Another way people can get mono is through kissing, which is why some call it “the kissing disease.”

However, it is possible to get the virus that causes mono from other bodily fluids, such as semen or blood.

Keep reading to learn how mono can be an STI, how it can spread, how long it is contagious, and whether mono is the same as herpes.

A woman sat in bed with mono next to her partner who is asleep.Share on Pinterest
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Mono can be an STI in some cases. Although the main method of transmission is contact with saliva, it can also spread through contact with blood or semen during sex.

When people refer to “herpes,” they often mean genital herpes. There are two viruses that can cause this condition: Herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2).

In contrast, the virus that usually causes mono is the Epstein-Barr virus (EBV). This is a distinct type of virus, so mono and genital herpes are two separate conditions.

The confusion comes from the fact that EBV belongs to the same family of viruses as HSV-1 and HSV-2, known collectively as herpesviruses. This large group of viruses includes eight that can affect humans, including:

The main way mono spreads is through saliva. This can occur while kissing, but there are many other ways a person could come into contact with the virus. For example, they might touch or use:

  • another person’s toothbrush, lip balm, or inhaler
  • unwashed drinking glasses or cutlery
  • shared cigarettes
  • a toy that a child has drooled on

Mono is contagious for about 6 months.

Mono and its symptoms usually go away in around 2–4 weeks. However, the virus that causes mono stays in the body, becoming inactive once the illness subsides.

The following symptoms may manifest slowly and may not all appear at the same time:

  • extreme tiredness
  • sore throat
  • swollen lymph nodes in the armpit and neck
  • rash
  • fever
  • headache
  • body aches

If mono symptoms persist for a long time, keep getting worse, or a person gets better and then worse again, they should contact a doctor for advice.

In rare cases, EBV can lead to serious illness. People should seek immediate help by calling 911 or going to an emergency room if alarming symptoms develop, such as:

  • tenderness in the left upper abdomen and pain in the left shoulder, which may indicate splenic rupture
  • difficulty breathing
  • a stiff neck
  • a rash that does not disappear under a glass
  • vomiting
  • confusion
  • vision changes
  • seizures
  • paralysis
  • difficulty staying awake
  • loss of consciousness

Below are answers to commonly asked questions about mono:

Can you kiss when you have mono?

Kissing while having mono can spread EBV. To avoid transmitting EBV to others, people should refrain from this until there is no longer a risk of contagion.

Does mono mean my partner is cheating?

No, not necessarily. Contact with saliva is the main mode of transmission, and this could happen in a sexual or nonsexual situation. Semen and blood contact can also cause EBV to spread.

How can you get mono without kissing?

Sharing drinking glasses, eating utensils, or personal care products that touch the lips or mouth could all spread mono. Saliva that contains the virus that causes mono can be in many places around the home, school, or workplace.

Mono can be an STI, as it may transmit via semen. However, the main way it spreads is through contact with saliva. This can occur in a sexual situation, such as when people are kissing. However, it can also happen in nonsexual situations, such as when sharing a cigarette or using someone else’s drinking glass.

A person getting mono does not necessarily mean they have been unfaithful to a partner. Mono is also not the same as genital herpes.

Mono may be contagious for around 6 months. In most people, mono symptoms such as sore throat and swollen lymph nodes get better in 2–4 weeks. The tiredness may take several weeks longer to disappear. Sometimes, the symptoms will last 6 months or longer.