Moreover, the fact that antibodies to HTLV-1 were absent in all patients with NMOSD suggests that HTLV-1 is not a common trigger of acute attacks in patients with AQP4-Ab positive NMOSD, a disorder in which relapses are often preceded by infection, in populations with high HTLV-1 seroprevalence. This evidence concerns the gene AQP4 and infection.