A New Measure for Assessing the Public Health Response to a Middle East Respiratory Syndrome Coronavirus Outbreak

Cho, Sung-il

A conceptual framework to describe the contact monitoring process is shown in Figure 1 . The figure represents a process in which a contact is infected by the index case, develops symptoms after an incubation period, and obtains a diagnosis after a certain delay. Monitoring as a function of time T, specifically, the number of infected cases being monitored at time T (M[T]), implies appropriate public health actions such as quarantine of a high risk contact or isolation of a patient for specialized treatment. If the infected individual is not identified early enough and monitoring starts only at the time of diagnosis (TD), this patient may have already infected some of the contacts during the delay in detection. Missing any of them from contact tracing may result in further spread of the disease. If monitoring starts soon after the time of symptom onset (TS) as the patient visits health care facilities, there will be shorter delay and smaller number of contacts, with a reduced chance of spread. If monitoring starts at an even earlier time-as soon as a contact is identified and before any symp-toms develop (TC), there should be little infectivity at this point and no further cases will occur. However, this approach will involve a greater effort to monitor all the contacts as soon as they are identified, regardless of any symptoms.