A 31-year-old woman is 8 months pregnant with her first child. Her general health is completely normal, as is the health of her developing fetus. She works in an office as a data entry clerk. One day she develops a fever, nausea, and muscle aches. She decides to leave work early and rest at home. Her symptoms persist for 2 days but do not develop any further. Three weeks later, she realizes that the fetus is not as active as it had been in the days' prior. After 24 hours of virtually no movement, she calls her physician. In a whirlwind of panic, she undergoes a sonogram and is told a fetal heartbeat can no longer be detected. Based upon all of the information obtained through specimen testing, along with the patient's symptoms, the pathogen is most likely .