As folate is vital in the first trimester of pregnancy for healthy fetal development, the use of antifolates is strongly contraindicated in pregnancy and carries significant teratogenic risk. Low doses of methotrexate can deplete folate stores and cause side-effects that are similar to folate deficiency.
Cause of Adult Mumps. Adult mumps is caused by an infection with the mumps virus, which is found worldwide. The mumps virus is an RNA (ribonucleic acid) virus from the family Paramyxovirus of the genus Rubulavirus. The mumps virus only infects humans.
Encephalitis also can be caused by the herpes simplex virus, which also causes cold sores and genital herpes. This type of encephalitis is less common but tends to be more severe. The mumps and measles viruses also can cause encephalitis, with mumps occurring most often in the winter or spring.