How can i get data set of illness and not illness people?
The data set will be available on Genbank, you simply search for the "authors surname and HBV" and their entire data set should be revealed. 

The HBV genome is 5Kb, the smallest viral genome so its not alot of data. 

I am confused by "Genotype B nucleotide sequence and non-HBV nucleotide sequences". What I suspect is the investigators looked at HBV genotype B in comparison to HBV genotypes A, C to I. Essentially they wanted to assess the relationship between genetic variation and pathogenesis, which is an attempt to assess virus-induced cancer. Obviously I don't know the paper but I'm aware of the basic research front in this area. HBV has a very wierd evolution and I personally wouldn't want to investigate it.