The public acquires only
14% of its pets from shelters
48% get their pets as strays, from friends, from animal rescuers,
38% get their pets from breeders or pet stores
Source: The Humane Society of the United States

Between 4 and 15 million cats and dogs are euthanized each year ~ this is
just an educated guess by
Source: The Humane Society of the United States

How the pets get to the shelters.

42.5 percent of pets that entered animal shelters were submitted by animal
control authorities and nearly
30 percent were surrendered by their owners.
The remainder were relinquished by other sources.

"Some of the reasons pet owners cited for giving up their pets to shelters
may be resolved through educational or other types of programs,"

Salman said. "Most of the problems are really not with the animals, but
rather with pet owners who may not be knowledgeable enough about or prepared
for the realities of owning a pet."
National Council on Pet Population Study and Policy

I agree, the truth is, I was headed for my local shelter today and see if I
could volunteer several days a week.
Or even just on saturdays.

I know many of you volunteer, and just wanted to get some feedback about it.
I'm sure you understand my reasons for asking about viruses. I'm not trying
to injure the meager 14% of people who get thier pets from a shelter.(see
not above)