What is mononucleosis?
Mononucleosis, also called “mono,” is a common illness that can leave you feeling tired and weak for weeks or months. Mono goes away on its own, but lots of rest and good self-care can help you feel better.
What causes mono?
Mono usually is caused by the Epstein-Barr virus (EBV). It is most often seen in teens and young adults. Children can get the virus, but it often goes unnoticed because their symptoms are mild. Older adults usually don’t get mono, because they have immunity to the virus.
Mono can be spread through contact with saliva, mucus from the nose and throat, and sometimes tears. Because the virus can be spread through kissing, it has earned the nickname the “kissing disease.” If you have mono, you can avoid passing the virus to others by not kissing anyone and by not sharing things like drinking glasses, eating utensils, or toothbrushes.
As soon as you get over mono, your symptoms will go away for good, but you will always carry the virus that caused it. The virus may become active from time to time without causing any symptoms. When the virus is active, it can be spread to others. Almost everyone has been infected with the mono virus by adulthood.
What are the symptoms?
The most common symptoms of mono are a high fever, a severe sore throat, swollen lymph nodes (sometimes called swollen glands) and tonsils, and weakness and fatigue. Symptoms usually start 4 to 6 weeks after you are exposed to the virus.
Mono can cause the spleen to swell. Severe pain in the upper left part of your belly may mean that your spleen has burst. This is an emergency.
How is mono diagnosed?
Your doctor will ask you questions about your symptoms and will examine you. You may also need blood tests to check for signs of mono. Blood tests can also help rule out other causes of your symptoms.
How is it treated?
Usually only self-care is needed for mono.
- Get plenty of rest. You need bed rest until you feel well enough to be up. This could keep you away from school or work for a little while.
- Gargle with salt water or use throat lozenges to soothe your sore throat. This is okay for children as long as they are old enough.
- Take acetaminophen (such as Tylenol) or ibuprofen (such as Advil) to reduce fever and relieve a sore throat and headaches. Never give aspirin to someone younger than age 20 years, because it can cause Reye syndrome, a serious illness. Be safe with medicines. Read and follow all instructions on the label.
- Avoid contact sports and heavy lifting. Your spleen may be enlarged, and an impact or straining could cause it to burst.
In severe cases, medicines called corticosteroids may be used to reduce swelling of the throat, tonsils, or spleen.
Mono is usually caused by the Epstein-Barr virus (EBV).
How mono is spread
The Epstein-Barr virus (EBV) can be found in saliva and mucus (and sometimes tears). EBV is not spread by casual contact. You can live in the same house with a person who has mono and never become infected with the virus. But a person who has a weakened immune system may be at higher risk for mono. It’s possible that people who have had mono can spread the virus even though they no longer have symptoms.
- EBV lives and grows in the nose and throat. Any fluid that comes from these parts of the body, including saliva, tears, or mucus, can be infected with the virus. The virus (EBV) is spread when people come in contact with infected fluids.
- EBV can be spread through intimate contact or sharing of saliva. (A brief kiss on the lips is not likely to spread EBV. It is spread when saliva from an infected person gets into another person’s mouth.)
- You can get EBV if you share a drinking glass or eating utensils with an infected person (through sharing saliva).
- In rare cases, someone can get an infection after receiving blood from a person who is infected with EBV.
- Most people get infected with EBV at some point in their lives but never get mono symptoms. EBV “sleeps” (is dormant) in the body. It can become active from time to time and spread to others. When it reactivates, most people do not have symptoms. Many healthy people carry the virus and spread it every now and then throughout their lives. Lifetime carriers of EBV are the most common source of EBV infection.
Contagious and incubation period
- You can pass the Epstein-Barr virus (EBV) to others for several weeks or months during and after the time you are first infected with EBV. The virus can also become active and spread to others from time to time throughout your life.
- There is a small risk of spreading EBV through blood products. If you know you have mono, you should not donate blood.
- It takes 4 to 6 weeks for symptoms to develop after you come in contact with EBV. This is called the incubation period.
Not everyone infected with the virus that causes mono (Epstein-Barr virus, or EBV) has symptoms. This is especially true for young children, who may have a fever but no other symptoms. People ages 15 to 24 are most likely to have obvious symptoms.
The most common symptoms of mono are:
- Fever, which may range from 101°F (38.3°C) to 104°F (40°C), and chills.
- Sore throat, often with white patches on the tonsils (which may look like strep throat).
- Swollen lymph nodes all over the body, especially the lymph nodes in the neck.
- Swollen tonsils.
- Headache or body aches.
- Fatigue and a lack of energy.
- Loss of appetite.
- Pain in the upper left part of the abdomen, which may mean that the spleen has become enlarged.
These symptoms usually get better in about 1 or 2 months.
You can get a rash if you take the antibiotics amoxicillin or ampicillin when you have mono. These antibiotics are often prescribed for other causes of sore throat, such as strep throat, and might be prescribed for you before the doctor knows you have mono. The rash is not an allergic reaction.footnote 1
Mono may cause your spleen to swell to 2 or 3 times its normal size. An enlarged spleen occurs in up to 75 out of 100 people who have mono.footnote 2 A blow to the abdomen can cause an enlarged spleen to rupture. To reduce this risk, avoid heavy lifting and contact sports for several weeks after you become ill with mono or until your doctor says it is safe. In very rare cases, the spleen may rupture on its own.
Symptoms of mono can be more severe and last longer in people who have an impaired immune system or a rare genetic condition called X-linked lymphoproliferative syndrome.
The symptoms of infectious mononucleosis, such as a sore throat and fever, also are found in many other conditions.
Usually mono is a mild illness that goes away without treatment after several weeks. When you have mono, your symptoms may come and go, and your symptoms may change with time.
- A sore throat is worst during the first 3 to 5 days and gradually improves over the next 7 to 10 days.
- Fever may last 10 to 14 days. Usually it is mild during the last 5 to 7 days. If you have a fever, you should stay home from work or school until the fever goes away. You can then go back to your normal activities if you feel up to it.
- Swollen lymph nodes (sometimes called swollen glands) may last up to 4 weeks.
- It may take several weeks (even months) for your energy level to return to normal. Don’t try to rush this process. Pushing yourself too hard could make you feel worse. Give your body the rest it needs.
Mono can cause your spleen to enlarge, making it prone to injury. To reduce the risk of injuring your spleen, avoid heavy lifting and contact sports for several weeks after you become ill with mono (or until a doctor tells you it is okay).
If you know you have mono, you should not donate blood. Epstein-Barr virus (EBV) can be spread through blood products, although this is not common.
Complications of mono are rare but are most likely to develop in very young children, older adults who are in poor health, and people who have impaired immune systems.
In the past, both infectious mononucleosis and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) were thought to be caused by the Epstein-Barr virus. But it is now believed that even though both conditions have some similar symptoms, they are different diseases and ME/CFS is not caused by the Epstein-Barr virus.
What Increases Your Risk
Mono is usually caused by the Epstein-Barr virus (EBV). You are at increased risk of getting mono if you:
- Are age 15 to 24, especially if you are in close contact with many people. In the United States, college students, nurses, and people in the military are most likely to get mono.
- Have intimate contact with a person who has mono or an active EBV infection. (A brief kiss on the lips is not likely to spread EBV. It is spread when saliva from an infected person gets into another person’s mouth.)
- Share drinking glasses, eating utensils, dishes, or a toothbrush with an infected person. A person does not have to have symptoms of mono to spread EBV.
After you have been infected with EBV, the virus may stay in your body for the rest of your life. But you will not get mono again.
EBV is not spread through the air. You can live with a person who has mono and never become infected with the virus.
Most people have been infected with EBV before, so they usually don’t get mono when they are exposed to a person who has it.
When should you call your doctor?
If you have been diagnosed with mono, seek care immediately if:
- You have severe pain in the upper left part of your abdomen. This may mean that your spleen has ruptured. Rupture of an enlarged spleen caused by mono is rare. It is most likely to happen because of a blow to the abdomen.
- Your tonsils become so swollen that you find it difficult to breathe or swallow.
If you have not been diagnosed with mono and you have a severe sore throat that has lasted longer than 2 to 3 days after trying home treatment, call your doctor in 1 to 2 days.
If you have not been diagnosed with mono and have tried home treatment for 7 to 10 days, contact your doctor if you have:
- A lack of energy.
- Body aches.
- Swollen lymph nodes (sometimes called swollen glands).
Most cases of mono do not require treatment, but you still need to take care of yourself until the illness goes away. You should see your doctor to make sure your symptoms are not caused by a treatable infection, such as strep throat.
Who to see
The following health professionals can diagnose and treat mono:
Exams and Tests
A medical history and physical exam are the most important ways a doctor can diagnose mono. During the medical history and physical exam, your doctor will ask questions about your symptoms and possible exposure to the disease. Your doctor will also examine you for signs of the infection. This may include looking at your throat, checking your skin, and pressing on your abdomen.
Blood tests to help confirm the diagnosis include:
- Mononucleosis tests (including the monospot test and EBV antibody test). It is possible for the monospot test to come back negative early in the course of the infection (false negative).
- Complete blood count (CBC). A CBC may be done to rule out other infections or complications of mono.
Other tests may be done if complications of mono occur or if the mononucleosis tests are negative.
- Liver tests may be done to find out whether the virus has affected your liver.
- If the mononucleosis test is negative, your doctor may test you for an infection with cytomegalovirus (CMV) or other organisms. CMV can cause an illness that is like mono.
Usually no treatment for mono is needed other than self-care at home.
Most people recover from mono after several weeks. But for some, it may take several months before they regain their normal energy levels. This extended period of fatigue is not the same as having myalgic encephalomyelitis/chronic fatigue syndrome.
In severe cases, corticosteroids may be used to reduce swelling of the throat, tonsils, or spleen. This type of steroid use may also decrease the overall length and severity of illness from infectious mono.
For more information, see Home Treatment.
The virus that causes mono (Epstein-Barr virus) isn’t spread as easily as most people think. If you follow these tips, you can reduce the chance of spreading or catching mono.
- Don’t kiss or share dishes or eating utensils with someone who has mono. (A brief kiss on the lips is not likely to spread Epstein-Barr virus. It is spread when saliva from an infected person gets into another person’s mouth.)
- Don’t donate blood if you have mono. Although it is unusual for the Epstein-Barr virus to be spread through blood, it is possible.
Self-care is usually all that is needed if you have mono. Unless you have a serious complication of mono (which rarely occurs), no medicine or treatment will speed your recovery. Most people who have mono recover without problems. There are many steps you can take to ease the symptoms until you are back to normal.
- Listen to your body. Don’t push yourself when you have mono. If you feel tired, it is important to rest and give your body a chance to heal.
- Rest in bed. You probably won’t feel like working or going to school anyway, and rest is very important.
- Avoid contact sports and heavy lifting for 4 weeks after you become ill with mono (or until a doctor tells you it is okay) to reduce the risk of injuring your spleen.
- Take acetaminophen (such as Tylenol) or ibuprofen (such as Advil) to reduce fever and to relieve a headache and sore throat. Do not give aspirin to anyone under the age of 20, because its use has been linked with Reye syndrome, a serious illness. Be safe with medicines. Read and follow all instructions on the label.
- Soothe your sore throat with cool liquids and saltwater gargles [1 tsp (5 g) of salt in 8 fl oz (237 mL) of warm water]. Hard candies or throat lozenges might help too. If your child has a sore throat, candy or lozenges are okay if he or she is at least 4 years old. And most children can gargle at age 8 and older.
- Drink plenty of fluids, especially if you have a fever. This will help prevent dehydration.
Your symptoms will gradually improve over 2 to 3 weeks. You should be able to return to your normal activities within about a month. Let your symptoms be your guide. You may need to adjust your school and work schedule to take advantage of times when you feel more energetic. If you feel better, try to get back to your routine sooner. But remember not to push yourself.
There are no specific medicines used to treat mono. Over-the-counter medicines may be used to help treat the symptoms of mono.
Over-the-counter pain relievers, including acetaminophen (such as Tylenol) and ibuprofen (such as Advil), may be used to relieve headaches and a sore throat. Do not give aspirin to anyone under the age of 20, because its use has been linked with Reye syndrome, a serious illness.
In severe cases, corticosteroids may be used to reduce swelling of the throat, tonsils, or spleen.
Taking antibiotics such as amoxicillin or ampicillin may cause a rash in many people who have mono. A rash caused by antibiotics can often be a first sign that the person has mono. The rash is not an allergic reaction.footnote 1
Antiviral drugs do not improve the symptoms of mono or shorten the length of the illness.footnote 3
What to think about
Nonprescription medicines are commonly used to relieve symptoms, but they do not shorten the duration of the illness.
There is no surgical treatment for mono. Emergency surgery may be needed to remove a ruptured spleen if this complication occurs.
- American Academy of Pediatrics (2012). Epstein-Barr virus infections (infectious mononucleosis). In LK Pickering et al., eds., Red Book: 2012 Report of the Committee on Infectious Diseases, 29th ed., pp. 318–321. Elk Grove Village, IL: American Academy of Pediatrics.
- Levin MJ, Weinberg A (2012). Infections: Viral and rickettsial. In WW Hay Jr et al., eds., Current Diagnosis and Treatment: Pediatrics, 21st ed., pp. 1177–1219. New York: McGraw-Hill.
- Hirsch MS (2014). Herpesvirus infections. In EG Nabel et al., eds., Scientific American Medicine, chap. 224. Hamilton, ON: BC Decker. https://www.deckerip.com/decker/scientific-american-medicine/chapter/224/pdf/. Accessed December 15, 2016.
Other Works Consulted
- Belazarian LT, et al. (2012). Exanthematous viral diseases. In LA Goldman et al., eds., Fitzpatrick’s Dermatology in General Medicine, 8th ed., vol. 2, pp. 2337–2366. New York: McGraw-Hill.
- Levin M, et al. (2014). Infections: Viral and rickettsial. In WW Hay Jr et al., eds., Current Diagnosis and Treatment: Pediatrics, 22nd ed., pp. 1227–1270. New York: McGraw-Hill.
Current as of: June 9, 2019
Author: Healthwise Staff
Medical Review:E. Gregory Thompson, MD – Internal Medicine & John Pope, MD, MPH – Pediatrics & Adam Husney, MD – Family Medicine & Kathleen Romito, MD – Family Medicine & Caroline S. Rhoads, MD – Internal Medicine