The plot is a ruin
So let me get this straight, the military found the girl, but without being constrained or whatever he let the parasite be transferred to him?
Then while the parasite has been transferred to him, let's say he passed out but he's sent on the boat meanwhile.
So the blood tests are negative for both him and angela. Yet to show she's not infected Angela bites him...
So if she was infected the blood would transmit the virus, but she's not hence her tests were negative.
Then why was the soldier test negative too?