"Virgin fiber," basically, is just fiber that comes straight from wood, and is not recycled. Many environmentalists use the term "virgin forest" very loosely, using it to refer only to forests that have been untouched for hundreds of years. Second and third growth forests, or farmed forests, don't actually count as real trees.

Kimberley Clark, as just one example I looked up, gets about 97 percent of its virgin fiber from forest sources certified by the following organizations:

-- Forest Stewardship Council (FSC). We give preference to FSC-certified wood fiber where it is
available and meets product performance requirements and competitive market conditions
-- Sustainable Forest Initiative (SFI)
-- Canadian Standards Association’s National Sustainable Forest Management Standards (CSA)
-- Sistema Brasileiro de Certificação Florestal (CERFLOR) in Brazil
-- Program for the Endorsement of Forest Certification Schemes (PEFC) in Europe

The goal is to move all sources into the FSC category.