Yes... and no. There is selection pressure on the virus to avoid severe symptoms, because hosts that are up and being sociable are better vectors for the virus

Yes... and no. There is selection pressure on the virus to avoid severe symptoms, because hosts that are up and being sociable are better vectors for the virus than hosts that are in bed or hooked up to tubes in hospital. However, there is also selection pressure for the virus to infect cells more efficiently and reproduce in greater quantities. These traits tend to correlate with the virus being more dangerous to the host. The way the virus transmits before the host becomes symptomatic is quite an effective strategy for the virus, and means the selection pressure for the virus to not cause symptoms is less than it otherwise would be.