Signs of Mononucleosis

How can you tell if have mono? Mononucleosis, or “mono”, is an infection that is caused by the Epstein-Barr virus, which infects B cells (B-lymphocytes), producing a reactive lymphocytosis and atypical T cells (T-lymphocytes) known as Downey bodies. The virus is contagious via saliva, which is why it’s sometimes called “kissing disease.”

It is also known as Pfeiffer’s disease, or glandular fever in English-speaking countries outside North America. Mono occurs most often in 15 to 17-year-olds. However, you can get it at any age.

Signs and symptoms of mononucleosis include fever, sore throat, muscle weakness, metal fatigue, and swollen lymph glands. Sometimes, a swollen spleen (splenomegaly, which may lead to rupture) or liver (hepatomegaly) may develop. Heart problems or involvement of the central nervous system occurs only rarely, and infectious mononucleosis is almost never fatal. Other signs seen more rarely are loss of appetite, depression, diarrhea, skin rashes, headache, dizziness and disorientation.

There are no known associations between active EBV infection and problems during pregnancy, such as miscarriages or birth defects. Although the symptoms of infectious mononucleosis usually resolve in 1 or 2 months, EBV remains dormant or latent in a few cells in the throat and blood for the rest of the person’s life.

Periodically, the virus can reactivate and is commonly found in the saliva of infected persons. This reactivation usually occurs without symptoms of illness.

Whats in a Name

The name mononucleosis derives from the fact that the number of mononuclear leukocytes (white blood cells with a one-lobed nucleus) rises significantly during infection. There are two main types of mononuclear leukocytes: monocytes and lymphocytes.

Normal blood values are 35% of all white blood cells. With infectious mononucleosis, this can rise to 50-70%. Also, the total white blood count may increase to 10,000-20,000 per cubic millimeter, the count is normally 4,000-11,000.

The monospot test is a test for mononucleosis that takes only a few minutes; it tests for heterophile antibodies produced by the human immune system in response to EBV infection. Commercially available test kits (Monolatex, Mono-Latex, Mono-Lex, Mono-Plus and Clearview IM) are 70-92% sensitive and 96-100% specific.

If you have a positive mono test, an increased number of white blood cells, reactive lymphocytes, and symptoms of mononucleosis, then you will be diagnosed with infectious mononucleosis. If symptoms and reactive lymphocytes are present but the mono test is negative, then it may be too early to detect the heterophile antibodies or the affected patient may be in the small number of people who do not make heterophile antibodies.

Other EBV antibodies and/or a repeat mono test may be performed to help confirm or rule out the mononucleosis diagnosis.

Image: Day Donaldson/Flickr

Like This Article? Sciencebeta has a free 3 times weekly digest of the most interesting and intriguing articles in psychology, neuroscience, neurology, and cognitive sciences. Want to give it a try? Subscribe right here