What are the connotations of "Vet'hi Nidasah alav"?
Rashi: It means that, like the Nidah herself, the man (is an Av ha'Tum'ah, and) renders Tamei Adam and K'lei Cheres.
And what does the latter half of the Pasuk, which is seemingly superfluous, teach us?
Rashi (in Yoma, 6b) and Rashbam: It teaches us that, although the Mishkav of the Nidah herself is Metamei Adam ve'Keilim, the Mishkav of the Bo'el Nidah is only Metamei food and drink. 1
What is underneath a Bo'el Nidah (Mishkav) has the same Din as the covering of a Zav (Rashbam, citing Nidah, 32b).