When Mono Takes You Out of the Action (cont.)

Two viruses can cause mono: Epstein-Barr virus (EBV) and cytomegalovirus (CMV). Both viruses are in the herpes family, whose other members include viruses responsible for cold sores and chickenpox.

EBV causes 85 percent of mono cases. About half of all children are infected with EBV before they're 5, but at that young age, it usually doesn't cause any symptoms. If you don't become infected with EBV until you're a teen or older, you're more likely to develop mono symptoms. After you're infected, the virus stays with you for life, but usually doesn't cause any additional symptoms. Still, every now and then you may produce viral particles in your saliva that can transmit the virus to other people, even though you feel perfectly fine. By age 40, 85 to 90 percent of Americans have EBV antibodies, indicating they have the virus in their systems and are immune to further EBV infection.

CMV is also a very common virus. About 85 percent of the U.S. population is infected with it by the time they reach adulthood. As with EBV, CMV is frequently symptomless, and mono most often results when infection occurs in the teens and 20s. Sore throat is less common in people who have CMV mono than in those infected with EBV.

As another one of its nicknames -- glandular fever -- implies, perhaps the most distinguishing mono symptom is enlarged glands or lymph nodes, especially in the neck, but also in the armpit and groin.

Another common mono symptom is fever. A temperature as high as 39.5 degrees Celsius (103 degrees Fahrenheit) is not uncommon. Other symptoms include a tired achy feeling, appetite loss, white patches on the back of the throat, and tonsillitis.

"My tonsils got so swollen they were touching each other in back," says Heidi Palombo of Annandale, Va., who had mono when she was a senior in college. She recalls her throat being "so hot and swollen that the only thing that felt good was ice water."

Cold drinks and frozen desserts are both ways to relieve sore throat symptoms. Doctors also recommend gargling with saltwater (about half a teaspoon salt to 8 ounces of warm water) and sucking on throat lozenges available over the counter in pharmacies and other stores. If throat or tonsils are infected, a throat culture should be taken so the doctor can prescribe an appropriate antibiotic. Ampicillin is usually not recommended because it sometimes causes a rash that can be confused with the pink, measles-like rash that 1 out of 5 mono patients develops.