If you have both parents with long ears and some of the offsprings have short ears, you can say both parents are heterozygous for this. Both have a dominant (long ear), and a recessive allele (short ear).
To prove this, you can draw a Punnett square, and you'll see the probabilities of the offsprings.
 
        
             
        
        
        
there should be an image or something?
 
        
                    
             
        
        
        
It spreads by one person being around another
everyone who comes in contact with someone who has the virus