This was not alignment free: "and further filtered of human content using Bowtie40. The prinseq-lite utility41 was used to remove low-complexity sequences (using a DUST threshold of 7) and short reads <45 nucleotides. Remaining reads were aligned to the RefSeq collection of viral genomes (n=3,590 excluding bacterial phages), downloaded on 19 Dec 2012."
I still don't understand how one can have "coverage" and classification to "source genome" withoug alignment.
how does this work without alignment?
Do you mean you have a method of removing contaminations or sequencing errors without mapping to a genome?
Are you looking forward at performing a de novo assembly ?