WARNING. I have looked N.Brother Island many times working on the waterfront. A) It is a DEC/ NYC Parks controlled island. B) The police boat likes to tie up there a lot between patrols. C) That is the last known residence of typhoid Mary. The island was at one time a quarantine station. It is my understanding that there is a chance that the viruses dormant, but not dead. One reason the city does not allow trekking around there is the fear of someone being infected.
Just food for thought.
J~