The question now is how sheryl will survive?
/Speculation mode ON
According to Dr. Klan the V-type infection "is transmitted via blood or bodily fluids" So the new infected will be Alto, because they kissed in ep 10. After that, Alto kiss Ranka for the movie scene. So in certain point he must start to have the symptoms of the disease.
Assuming that the fairy proyect was trying to replicate Q1 the most probable thing is that Ranka will be the cure, but first they all were entering panic since her songtress of hope might be sick, at the time they discover the real nature of the skills of ranka before the bitch (Grace) could do something. Besides, of course Ranka will do everything to save Alto
/Speculation mode OFF
Sounds good, but as always has a 99.99% of probabilities that I'm dead wrong xD