I am a vet nurse and unfortunately I think the reason that the Parvo virus is becoming more common is that people can not afford to get their dogs (and cats) vaccinated. We send out reminders 1 month before a vaccination is due and in the last year or so we see less and less people coming back for their pets booster shots. It is sad but some people have more important things to spend their money on and it is the animals that get put on hold.
We also saw a huge amount of dogs with Flee allergy dermatitis last spring/summer because of people not been able to afford flee treatment. It is unfortunate that it happens and the problems we see as a result are sometimes horrendous.