How is CMV and the BK virus spread? Why Valcyte if not at risk?

I have asked the transplant team why they started Jenna on Valcyte again. They said, because of the major dosing of anti-rejection infusions in an attempt to save her kidney, she is at higher risk for BK Virus and CMV. But, I said, she is not at risk to get those without swapping spit (or any other bodily fluids) and she and her donor were CMV and HBV negative - so why do it? They said to protect her in the future. The problem is that the Valcyte is possibly contributing to her very low WBC and she's on barely any Prograf or Cellcept.

Does anyone else have any ideas about how long the Valcyte should continue? She is taking (1) 450 mg tablet twice a week, so it isn't much. We have called the team but no response yet.

How is CMV spread?

* Person to person contact (such as, kissing, sexual contact, and getting saliva or urine on your hands and then touching your eyes, or the inside of your nose or mouth)
* Through the breast milk of an infected woman who is breast feeding
* Infected pregnant women can pass the virus to their unborn babies
* Blood transfusions and organ transplantations

CMV is sometimes found in body fluids, including urine, saliva (spit), breast milk, blood, tears, semen, and vaginal fluids. A person can become infected with CMV when they come in contact with infected body fluids. However, people who are CMV-positive (have been infected with CMV sometime in the past) usually do not have virus in these fluids, so the chance of getting a CMV infection from casual contact is very small.
Contact with the saliva or urine of young children is a major cause of CMV infection among pregnant women.

Women who are pregnant or planning a pregnancy should follow hygienic practices (e.g., careful handwashing) to avoid CMV infection. Because young children are more likely to have CMV in their urine or saliva (spit) than are older children or adults, pregnant women who have young children or work with young children should be especially careful.
http://www.cdc.gov/cmv/faqs.htm#spread

Transmission of BK Virus

It is not known how this virus is transmitted. It is known, however, that the virus is spread from person to person, and not from an animal source. It has been suggested that this virus may be transmitted through respiratory fluids or urine, since infected individuals periodically excrete virus in the urine. A survey of 400 healthy blood donors was reported as showing that 82% were positive for BK virus.