Bartonella is a genus of bacteria, six of which are now known to infect humans. There is evidence of bartonella infections dating back to about 2,000 B.C.E., and it has likely been affecting humans longer than that.
Like staphylococcus, bartonella is opportunistic and rarely infects healthy people. However, unlike staph, bartonella is not particularly ubiquitous in the enviornment. It's usual route of infection is through a vector, such as fleas, ticks, sand flies and mosquitos. People such as intravenous drug users and those who are immunocompromised are particularly at risk.
One of the difficulties in recognizing bartonella is that it's symptoms are highly variable from species to species, and even from patient to patient. Although an animal or insect bite can be useful in a differential diagnosis, the disease can present withough such a bite.