To observe interference in a double slit experiment, what is important is that the wave remain coherent. What that means is, the wave, in an approximate momentum eigenstate, must keep all its components oscillating in phase in order to remain a wave.
We all know that any experiment you do to determine "which slit" the wave goes through will destroy this coherence and no intereference pattern will be observed.
So to do this experiment, you need to first prepare a human in a momentum eigenstate. This is practically impossible, because you need to make sure all 10^28 or so particles of the human are oscillating in phase, and you also need to protect them all from interacting with particles in the environment (which would become entangled with it and carry away coherences).
But if you could somehow prepare such a state, and then isolate it from air particles, radio waves, cosmic rays, cosmic microwave background, and measure electromagnetic radiation from the human (e.g. IR radiation from heat), and all beta decay products (like neutrinos, etc.), then in principle you could observe a human interference pattern.