I thought this idea was too good for it to get buried in another thread, so here's a new one I hope people could comment on. @natasa778 found this evidence that a protein associated with the mold Aspergillus Niger is theoretically similar to the HERV-W envelope protein. In principle couldn't that cause an auto-immune reaction against the HERV? Perhaps there are other similarities we haven't yet identified between other molds and other HERVs. In response to @Dufresne I mentioned why I think mold is involved in MECFS outbreaks: @Valentijn had this to say about the reliability of the Uniprot database: This study might be relevant, showing HERV proteins cause neuroinflammation.