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BackgroundContact tracing aims to prevent onward transmission of infectious diseases and data obtained during tracing provide unique information on transmission characteristics. A key performance indicator that has been proposed to evaluate contact tracing is the proportion of cases arising from known contacts. However, few empirical studies have investigated the effectiveness of contact tracing. MethodsUsing data collected between September 2020 and December 2021 in Belgium, we investigated the impact of contact tracing on SARS-CoV-2 transmission. We compared confirmed cases that were previously identified as a close contact to those that were not yet known, in terms of their traced contacts and secondary cases as well as the serial interval. In addition, we established contact and transmission patterns by age. FindingsPreviously traced, hence known, cases comprised 20% of all cases and they were linked to relatively fewer close contacts as well as fewer secondary cases and a lower secondary attack rate compared to cases that were not already known. In addition we observed a shorter serial interval for known cases. There was a relative increase in transmission from children to adults during circulation of the Delta and Omicron variants, without an increase in the extent of contact between these age groups. InterpretationThese results suggest that contact tracing in Belgium has been effective in reducing onward transmission and that individuals aware of their exposure to SARS-CoV-2 seemed more reserved in their social contact behaviour. Data from a reference period or region are needed to measure the impact of contact tracing in terms of the number of cases and deaths averted.
RESUMO
Objective. To determine the prevalence of Chlamydia trachomatis (CT); Neisseria gonorrhoeae (NG) and syphilis in pregnant women. Methods. A cross-sectional study was conducted among women attending antenatal care clinics (ANCs). Blood samples were tested for syphilis using the rapid plasma reagin (RPR) and treponemal haemaggluti- nation (TPHA) tests; CT and NG were diagnosed using a manual polymerase chain reaction assay on first-void urine samples. A socio-demographic questionnaire was completed. Results were compared with previous published data on sexually transmitted infection (STI) prevalence in Mozambique. Results. Blood and urine samples were collected from 1 119 and 835 women; respectively. The prevalence of CT was 4.1; and that of NG 2.5. The RPR test was positive in 5.2of the women; and 7.1had a positive TPHA test. Active syphiliswas found in 4.7. In univariate analysis; CT was associated with having had any level of education (p0.05); reactive RPR and TPHA were associated with illiteracy (p0.05); and TPHA was associated with age 25. Multivariate analysis did not show any significant association. In comparisonwith published data from 1993; a decline was observed for CT (p0.05); NG and syphilis (p0.001). Conclusions. Compared with available data; a decline of STI prevalence was observed in our setting. This might be the result of community-based education programmes focusing on changes to sexual behaviour; as well as the widespread use of the syndromic approach to managing STIs and the expansion of syphilis screening in primary health care settings. However; STI rates are still high; and the problem needs more concrete and sustained efforts for its control
