Download FASTA sequences for known viral reference genomes

Take a look at this report file for viral genomes.

I would only need DNA based viruses, and ones that infect humans

You can filter/parse out entries you need from it. Then download the genome sequence using EntrezDirect:

$ efetch -db nuccore -id NC_030449.1 -format fasta
>NC_030449.1 Unidentified circular ssDNA virus, complete genome
AAGTTCTGAGCGTAGGGCTAGTAGATAACGCACGTAGCTCAGATGACCGACGAAGACGGTCCTCGAGTAA
GAAACATAGTATTCATCATCAACGCAATCGATGGGGACGACCTTGTGTCCCAATTGCGTTTGCTCGATTT
CCAACACCCCACGTGGAAGCACGTAAAGTACTGTATCTATCAGCGAGAGTGCGGGGGTGAGGAGAATCGA
ATCCACTTCCAGGGCTACATGGAGTTCCACATCCAGCAGACCTATAAGCAGATTCATGCCATGGAAGGGA

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