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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