Background:Hantaviruses are the causative agents of two severe human diseases:hemorrhagic fever with renal syndrome (HFRS) in Eurasia and hantavirus cardiopulmonary syndrome (HCPS) in the Americas.Interferon lambda (IFN-λ) is a recently discovered group of small helical cytokines capable of inducing an antiviral response both in vitro and in vivo.