How do viral and bacterial infections affect a cbc?

It varies: A systemic bacterial infection is likely to increase the number of neutrophils, immature neutrophils, and angry-looking neutrohils (toxic granulation etc). Typhoid raises monocytes instead, whooping cough lymphocytes. Viral infections may raise total lymphocytes and/or atypical lymphs. Or either can suppress lymphs. It's tricky stuff.