[R-sig-Geo] presence-only data analysis

[SH]

Dear List:

I have googled to try to understand analyzing presence-only data and
predicting (?) species outbreaks.  Although I was able to find a few
papers, it is somewhat hard for me to figure out adapting my data.
Or, I may be looking at a wrong place.  Any suggestions/comments will
be appreciated.

I have a data set of GPS coordinates (long, lat) and presence-only
data (i.e., '1') based on counties.  I would like to estimate
likelihood of outbreak index.  For example, we know there is an
observation in (say) county A (or A, B, and C neighboring counties)
and I would like to know the likelihood (e.g., probabilities) of other
surrounding or neighboring counties (e.g., D, E, F, etc.).  Could you
give me any suggestion on analyzing this type of data?  I DON'T have
any covariates.

Thank you in advance,

SH