The English idiom "sicker than a dog" calls to mind the vivid and colorful memory that many people have of a dog vomiting, having non-productive intestinal spasms (dry heaves), or trying to pass a hard stool (the doggie jig). Dogs make no effort to conceal their distress, and so make loud noises that sound like a cross between hacking and barking while vomiting. To add to the imagery, sometimes the canine vomitus contains live parasitic worms, or pieces of offal that the dog has ingested.Clearly a human who is "sicker than a dog" is feeling rather unwell!
It is "feel as sick as a dog." The nurse became sick as a dog after contracting the flu. Food poisoning makes people sicker than dogs. Note: This is a very trite, overused expression.
No because he/she will get more sicker and sicker and sicker
Yes you can. You can get MUCH worse than it already is. 
sicker than lil Wayne cash flow
Scurvy dog
I was sick, but my brother was sicker, and our sister was the sickest of us all.
Other than being slang and Anglo American, the origin is unknowm
flicker
no
Sick and Sicker - 2010 was released on: USA: 29 October 2010
The origin of the hot dog (frankfurter) is Germany.