Zebrafish question

[Michelle Evans]

We have a Zebrafish that has developed a curved (or swollen) spine 
between the head and the dorsal fin and lays at the bottom of the 
tank and does not move unless provoked.  The other fish were 
picking on it so we separated it. It has remained the same (showed 
no signs of improvement or deterioration in the past week).  

We have had the fish for a little over a year and have not added any
new fish or creatures to the tank recently.

Does anyone have any I ideas on what is wrong with this fish and if 
there is anything we can do for it?  (Or for the other fish, if this one 
has exposed them to a disease?)  

Thank you in advance for any assistance you can provide.

Sincerely,

Michelle Evans
mlevan1 at ihpc.net