The evaluation of preventive and control measures on congenital syphilis in Guangdong Province, China: a time series modeling study

Abstract

Purpose: To evaluate the effectiveness of preventive and control measures for congenital syphilis (CS) implemented since 2012 in Guangdong Province, China, and assess the epidemic trend in the near future.

Methods: The interrupted time series analysis was conducted to compare changes in slope and level of CS notification rate from 2005 to 2020 in Guangdong Province and its three regions with different economic developmental levels. The ARIMA model was established to predict the new CS case number of Guangdong Province in 2021.

Results: A total of 12,687 CS cases were reported from 2005 to 2020. The CS notification rate of the province had been increasing until 2012 (128.55 cases per 100,000 live births) and then been decreasing constantly, hitting the lowest point in 2020 (5.76 cases per 100,000 live births). The severe epidemic cluster shifted from the developed region to underdeveloped ones over time. The effectiveness of the measures was proved by the significant change in the slope of the notification rate which was found in both of the provinces (- 18.18, 95% CI - 25.63 to - 10.75) and two less-developed regions (- 10.49, 95% CI - 13.13 to - 7.86 and - 32.89, 95% CI - 41.67 to - 24.10, respectively). In the developed region where the notification rate had already been decreasing in the pre-implementation period, implementing these measures also aided in hastening the rate of descent. The CS case number in 2021 was predicted to be 48, indicating a low-level epidemic.

Conclusions: The preventive and control measures have assisted Guangdong Province to control CS effectively, of which the supportive ones ensured a successful implementation. For resource-limited countries where CS is still endemic, especially guaranteeing the support in financial subsidy, professional training, supervision and so on might trigger the effectiveness of other measures and eventually make significant and sustainable progress.

Keywords: ARIMA; Congenital syphilis; Health policy; Interrupted time series analysis.

Fig. 1

The geographical distribution of congenital syphilis notification rate in each city of Guangdong Province from 2005 to 2020. Blue color represents Pearl River Delta region, green color represents the North ecological development zone and orange color represents the Eastern and Western wings

Fig. 2

The geographical distribution of CS notification rate in Guangdong Province in 2005 (a), 2011 (b) and 2020 (c). The darker color indicates a higher notification rate

Fig. 3

The annual congenital syphilis notification rate of Guangdong Province and three regions from 2005 to 2020

Fig. 4

Interrupted time series plot of annual change of congenital syphilis notification rate in Guangdong Province and the three regions before and after the implementation of the CS control measures. The intervention year was 2012. The slope and level change of the province were both significant, P < 0.05 (a). The level change in the PRD region (b) and North ecological development zone (d) were both significant, P < 0.05; the slope change in the North ecological development zone (Fig. 4d) and Eastern and Western wings (c) were both significant, P < 0.05

Fig. 5

The semi-logarithm line graph of the regional congenital syphilis notification rate from 2005 to 2019

Fig. 6

Monthly CS case number from 2005 to 2019 as reported (in black) and fitted by the optimal ARIMA model (in blue). ARIMA-based forecast of CS case number was presented in sky-blue color and displayed a 95% prediction interval (gray ribbon)