Gerry taking that risk at the end wasn't necessary
Gerry injected himself with an unknown bacteria/virus at the end because he couldn't ask the scientists!
Well they still could have communicated with each other.
Remember the phone?
He could have selected a bottle and held it close to the camera, so that they can read what it was and let's say suggested to ring for a long or short period of time for a yes/positive or no/negative answer.
This way he would have been sure what to take!
What do you think? Wasn't he smart enough to come up with the idea?