In larger jurisdictions there will be epidemiologists and others trained in tracking infectious disease outbreaks. There are those who monitor the health status of a community. There are social workers and data analysts. The list is a long one and it depends on local needs and programs. To those used to the clinical care environment it is also somewhat messy.
Public health is the application of health science in a community context.
It's science, but it's also politics. It follows that the information needs are very broad and overlap with subject areas that we don't usually think of as being health-related. Like their clinical counterparts, though, most public health workers will find PubMed to be an enormously useful tool and a great boon to their practice. But not all will. Environmental health is a good example of an information challenge encountered in public health.