Syphilis Correlations

This page examines the relationship between primary and secondary syphilis and congenital syphilis through time and cross-correlation analysis.

Are the cases of congenital syphilis correlated with the cases of primary and secondary syphilis through time?

An essential question in understanding the relationship between initial primary and secondary syphilis and the increases in observed congenital syphilis cases is whether the cases of congenital syphilis are correlated with the cases of primary and secondary syphilis through time.

Figure 1: Time series of Primary and Secondary Syphilis and Congenital Syphilis

Cross-correlation analysis

We can use cross-correlation to answer this question. Cross-correlation is a measure of the similarity between two time series as a function of the lag between them.

Figure 2: Cross-correlation of Primary and Secondary Syphilis and Congenital Syphilis

Based on this analysis, we can see that the highest levels of correlation are observed within a lag of 0-1 years indicating that increasing rates from the prior year (and the current year) are correlated with increasing rates of congenital syphilis.

This indicates that addressing areas with high current rates of primary and secondary syphilis may be a good way to address the increases in congenital syphilis cases.