Im 39 weeks pregnant with the bacteria streptococcus viridans in vagina. can this bacteria harm my baby while giving birth vaginally?

Very unlikely: Colonization of vaginal canal with streptococcus agalactiae aka group b strep has been well known to cause serious infection in newborns and young infants.

Group b strep: We don't usually test for strep viridans during pregnancy. I'm wondering if you mean strep agalactiae, also known as group b strep. This bacteria can cause sepsis, which is why we routinely test for it and if you have it, make sure that you get antibiotics during delivery.