The State Department said it had been 19 days since the hospital worker had handled fluid samples from the patient, just two days shy of the 21-day incubation period for Ebola. The hospital worker has self-monitored, including daily temperature checks, during that time for any symptoms of Ebola, and a doctor on board the ship is also helping the CDC keep track of the individual.
The worker reportedly boarded the cruise ship before being notified of the CDC about the quarantine and monitoring.
The case shows the extensiveness of the CDC's contact tracing tactics. As part of the process, the CDC individually contacts and conducts daily check-ups for 21 days — the potential incubation period for Ebola — on anyone who may have been directly exposed to an Ebola patient.
To learn more about contact tracing and Ebola, read Vox's card stack and watch the CDC's video explainer of the process: