In this study, sja-let-7 derived from the EVs of S. japonicum worms was overexpressed in a mouse model of carbon tetrachloride (CCL4)-induced LF to determine whether targeting the α2 chain of collagen type 1 (Col1α2) and the TGF-β/Smad signaling pathway can attenuate the progression of LF. The gene discussed is TGFB1; the disease is Lassa fever.