The short answer is that it's complicated. And at some level it depends whether you're just interested in capturing data (and whether that's going to be point of care by docs wearing PPE), or in driving workflow.
Doing retrospective data entry is straightforward. It involves building your organization's forms using the XForms or HTML Form Entry module, and having a plan to get the data entered. (E.g. data captured on paper in the red zone, scanned/photographed and transmitted out, then transcribed into OpenMRS.)
Also, check out the latest release of the CIEL dictionary, which contains a lot of content related to Ebola.
To do real-time data capture in red zone, you probably want forms that are designed to be easy to enter by tapping on a tablet while wearing PPE. OpenMRS doesn't have this out of the box (though I haven't tried building a plain form and just making everything 2x as large). The hackathon described here started working on this, but it isn't ready yet.
As far as driving ETU workflow, that's also not something that comes out of the box. (Basically, OpenMRS 2.1 is built around patients having multiple visits to a facility over time, whereas the ETU use case is about intensive care, and planning out ward rounds.)
Some community volunteers have been working on building an ETU EMR based on the needs of the Save the Children-operated Kerry Town ETU in Sierra Leone described here.
However since this is based on volunteer effort, it is making slow progress. You can see what's there (not much!) at devtest03.openmrs.org (login as admin/Admin123). What it will take to finish building this out is more developer effort...