Yup! Of the things we could be, we’re most like a virus, but parasite might work. Most parasites don’t kill their hosts, and if they do it’s a secondary action - it usually isn’t the parasite itself that kills the host, but some virus or bacteria the parasite transmits. There are some really nasty parasitic worms that will kill you, or make you wish you were dead.

We’re definitely not symbiotic, like most macro and many micro organisms are.

If we consider the the ecosystem as the host, we’re killing it; and individually, we’re micro-sized to the Earth, so I think virus is the most accurate model.