How would an intelligent species actually interact with an alien biotia?

We make a big deal about discovering life elsewhere in the universe, especially our own galaxy. Even if the place did not have intelligence, and if we got to the point of going to such a place, how would we actually interact with it? Even if we proved ahead of time that the astronauts could go there, then run around and breathe without a space suit (because presumably the gravity was similar, and the atmosphere had oxygen), and not die instantly… Wouldn't we be EXTREMELY worried about bacteria and viruses?

You can't just send a human to another earth and expect him to thrive. They will have bacteria and viruses that earthlings cannot deal with. And so it seems like a triple edged sword.

If any anlien species interact their bacteria and viruses will basically kill each other.

So, how would we overcome that problem if we discovered and decided to go to a would-be Pandora?

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