Reassessing a Large-Scale Syphilis Epidemic Using an Estimated Infection Date.

摘要

OBJECTIVES:: Timely ascertainment of syphilis cases is critical to initiating disease-control measures. Epidemic curves typically use the report date and may introduce lag-time bias into assessment. GOAL:: To reassess a large syphilis epidemic using an imputed infection date. STUDY:: We compared 2 types of epidemic curves-1 based on report date and 1 on estimated infection date-using the large 1993-2003 Baltimore epidemic as our model. RESULTS:: In general, the shape of the report curves did not accurately reflect the shape of the corresponding infection curves during the growth period (period of largest increase in incidence); during the hyperendemic period (period of highest incidence), peaks in report curves did not follow peaks in the infection curve by the appropriate lag time. There was a tendency for reporting data to underestimate infections during the growth period and overestimate infections during the hyperendemic period. A sensitivity analysis showed similar trends regardless of the length of stage-specific incubation period used. CONCLUSIONS:: Lag-time bias may be present when using epidemic curves based on report dates. Health departments should consider using an estimated infection date.