By #of species.
The point is that there are bats everywhere even though we don't much notice them and they have filled every niche they find. Bats appear to be an important reservoir for viruses and bugs and with their range of flight they can spread bugs in their droppings over a wide area. Saying the virus is in bats is useful but not all that surprising.
From a science POV the most interesting thing about this disease is how it is demonstrating that there is not a static equilibrium between hosts and microbes. It looks static just because we usually don't know what caused someone to have Flu Like Symptoms which are the body's standard response to infection. What we are learning is that like anti gunners, microbes area always testing the limits to see if there is anybody they can make sick!
There is deep research on the very start of the HIV infection in humans and they have traced it to a series of species jumps from primates to humans from like the 1920's through the 50's until it finally took hold and spread H2H. We can't (yet) tell which rare human infection will actually lead to any serious H2H infection. These events are getting lots of scrutiny since we don't know what it is we don't know that will be a good marker for long term spread. Folks shatter about "this virus only needs 4-5 mutations to be effective in humans..." but all mutations are not equally likely and some are very unfavorable from an evolutionary penalty POV and so we have what we call the species barrier that bugs have to get over to jump to a new host. Interesting stuff, exciting, not simple and not ready for prime time news talking heads and their sound bites...