Herpes simplex virus that could be determined by using serology or viral PCR.
Explanation:
Herpes simplex is an infection caused by the human herpes virus (HSV 1 and 2) that is characterized by the appearance of small blisters, especially clustered on the lips and genitals, but which can appear anywhere else in the body. The disease is highly contagious and can be transmitted through sex, or from mother to child during pregnancy. In pregnancy, herpes simplex may pose a concern. Inside the womb the child is protected but can become infected during normal birth. When infected, the newborn has extensive vesicular and ulcerative lesions on the face and chest.
Diagnosis in newborns can be done by viral culture, but this test is very evasive for babies, and the use of serology test or viral PCR is most recommended.
The Marburg virus wasn't mutating this early on, therefore the Coronavirus is much more deadlier and almost impossible to get a cure for, due to the rapid change in pathogens!