In the real world an alien virus wouldn't effect us. It would be like a cat virus affecting a human. Does it mean there is zero chance ? No, but almost zero. 
We would have to be on planet for awhile for it to jump species.
Still a decon chamber should exist and away teams should go through tests when they get back onboard and not let through until cleared.
Unless you have a face hugger clinging on..
	
		
			
		
		
	
				
			We would have to be on planet for awhile for it to jump species.
Still a decon chamber should exist and away teams should go through tests when they get back onboard and not let through until cleared.
Unless you have a face hugger clinging on..

				

	
