One lane for each of the two sample pools (FTLS and healthy controls), each consisting of 10 samples, was sequenced. The proportions of high-quality sequences in FTLS and control pools were 98.08% (10, 198 ,407/10,397,161) and 97.88% (10,250,809/ 10,472,315), respectively. Unique, high-quality sequence reads were then classified into broad taxonomic groups based on the taxonomy of the most frequent top-scoring BLAST matches for each sequence. Virus sequences constituted 0.0065% (67,969) and 0.0048% (50,677) of the reads in FTLS and control libraries, respectively (Table 3) . After contig assembly, the number of sequences phylotyped as ''viral'' decreased to 3,163 and 2,412, respectively, in the two pools (Table 4) . To screen for possible viruses, we focused exclusively on viruses that were present in patient sera.