Annie ( little mo) , heres what Mono is :

Infectious mononucleosis, also known as Pfeiffer's disease, mono (in the United States of America) and more commonly known as glandular fever in other English-speaking countries, is an infectious disease. It occurs most commonly in adolescents and young adults, where it is characterized by fever, sore throat, muscle soreness, and fatigue. Infectious mononucleosis typically produces a mild illness and is often asymptomatic. Mononucleosis is predominantly caused by the Epstein-Barr virus (EBV), which infects B cells (B-lymphocytes), producing a reactive lymphocytosis predominantly consisting of atypical lymphocytes, a specific type of T-cell that gives the disease its name.

The name "kissing disease" is often applied to mono in casual speech, as in developed countries it is most common at the same age when adolescents and young adults are initiating romantic behaviour. This co-occurrence is not apparent in undeveloped countries, where poor sanitation and close living arrangements cause the causative virus to be spread at a much earlier age, when the disease is mild and seldom diagnosed. Both males and females are susceptible to mononucleosis

Symptoms

• Fever—this varies, but is seen in nearly all cases.
• Enlarged and tender lymph nodes—particularly the posterior cervical lymph nodes.
• Sore throat—White patches on the tonsils and back of the throat are often seen
• Muscle weakness and Mental fatigue (sometimes extreme)

Additional symptoms include:

• Enlarged spleen (splenomegaly, which may lead to rupture) and/or liver (hepatomegaly)
• Petechial hemorrhage
• Abdominal pain - a possible symptom of a potentially fatal rupture of the spleen.^[1]
• Aching muscles
• Headache
• Loss of appetite
• Depression
• Diarrhea
• Dizziness or disorientation
• Inability to swallow, due to enlarged tonsils
• Dry cough
• Supra-orbital edema—the eyes become puffy and swollen—may occur in the early stages of infection

After an initial prodrome of 1-2 weeks, the fatigue of infectious mononucleosis often lasts from 1-2 months. The virus can remain dormant in the B cells indefinitely after symptoms have disappeared, and resurface at a later date. Many people exposed to the Epstein-Barr virus do not show symptoms of the disease, but carry the virus. This is especially true in children, in whom infection seldom causes more than a very mild cold which often goes undiagnosed. Children are typically just carriers of the disease. This feature, along with mono's long (4 to 6 week) incubation period, makes epidemiological control of the disease impractical. About 6% of people who have had infectious mononucleosis will relapse.^{[citation needed]}

Mononucleosis can cause the spleen to swell. Rupture may occur without trauma,^{[citation needed]} but impact to the spleen is also a factor. Other complications include hepatitis (inflammation of the liver) causing elevation of serum bilirubin (in approximately 40% of patients), jaundice (approximately 5% of cases), and anemia (a deficiency of red blood cells). In rare cases, death may result from severe hepatitis or splenic rupture.

Although most cases of mononucleosis are caused by the E.B. virus, the condition is defined by the clinical presentation and laboratory findings. Cytomegalovirus can produce a similar illness, usually with less throat pain, and also generate atypical lymphocyte proliferation. In recent years, as precise virological and serological studies are more commonly done to identify the actual causative virus, some clinicians have taken to use "mononucleosis" to refer only to the E.B. virus cases. Symptoms similar to those of mononucleosis can also be caused by adenovirus, acute HIV infection and the protozoan Toxoplasma gondii