How Can I Tell If My Child Has It?

I would think that the doctor would have to tell you. It is really hard to say, look on www.wikipedia.org or www.webmd.com and you should be able to find something out there.

I dont know too much about mercer.  I would call your pediatrician in the morning and see what they say.  I am sure if they are concerned about it then they will have tests ran to see if your children has been affected by it or not.  I would probably study some on the internet and research it a bit such as symptoms and how it is spread.  So you know what you are looking for and what to expect if they do come down with it.  That will also help prepare you with questions to ask your pediatrician or doctor that may arise.