Viral illnesses in the previous 70 to 90 days can greatly diminish the number and quality of sperm in a male, possibly impacting the results of a sperm analysis, which is why fertility clinics often do an STI check before the analysis. However, even if a male has just one copy of the cystic fibrosis gene, the vas deferens can still be repaired by surgery or sperm can be extracted from the testicle directly.