Shelley,
Go to emedicine.com
http://www.emedicine.com/ped/TOPIC447.HTM
for a full description of complement deficiencies in kids. My daughter had a "virus" for more than a year, too. Despite a high standard of living, our kids had multiple bouts of pneumonia and my daughter developed asthma at age 10. Chronic respiratory infections, unusal infections, and allergies are the hallmark of C2 def. in kids, and it's the rare pediatrician who is familiar with it. A simple blood test can rule complement deficiencies in or out.
The Irish and their diaspora descendants have the highest rate of complement deficiencies in the world. The Japanese have the highest rate of C9 deficiencies.
I hope this helps.