业已证实许多病毒能同时在孕妇与子宫内的胎儿中形成感染,如风疹病毒、单纯疱疹病毒,脊髓灰质炎病毒、巨细胞病毒、水痘-带状疱疹病毒、牛痘病毒以及天花病毒等均已在胎盘组织中检出,可以通过胎盘屏障。日本脑炎病毒对猪无有害影响,但母猪在妊娠早期感染此病毒时,可能会引起死产或畸形的仔猪。但过去未曾有报导过经人胎盘传染日本脑炎病毒 Many viruses have been shown to cause infections in both pregnant and uterine fetuses, such as rubella, herpes simplex, poliomyelitis, cytomegalovirus, varicella-zoster, vaccinia, and variola virus Placental tissue detected, can pass the placental barrier. Japanese encephalitis virus has no harmful effect on pigs, but sows may give birth to still malformed piglets when they are infected during the first trimester of pregnancy. However, no Japanese encephalitis virus has been reported in human placenta in the past