Contact tracing for sexually transmitted infections in Aotearoa New Zealand: a review of clinician-notified gonorrhoea and syphilis data

Keywords: contact tracing, gonorrhoea, New Zealand, partner notification, primary care, sexually transmitted infections, surveillance, syphilis.

Contact tracing (also referred to as partner notification) is an essential part of case management when a person is diagnosed with gonorrhoea or syphilis,¹ to minimise complications, reduce reinfection risk and break chains of transmission.^2,3 The diagnosing or treating clinician initiates discussion with their patient about the importance of identifying sexual contacts and informing them of the need for testing.¹ A review of research in Aotearoa New Zealand suggests that approaches to contact tracing for sexually transmitted infections (STIs) are inconsistent in primary care – documentation is often absent or incomplete, and follow up to check the success of contact tracing is uncommon.^4–6 However, when strategies are implemented to support clinicians to more effectively undertake contact tracing (eg with training, processes around documentation and follow up), this aspect of STI management can be significantly improved (see Supplementary Table S1).^7–11

In addition to effective case management, surveillance also plays an important role in reducing STI prevalence.¹² Surveillance is the ongoing, systematic collection, analysis, interpretation and dissemination of data, and is an important way to measure disease burden, monitor trends and identify disease outbreaks to inform public health planning, policy, strategies and allocation of health resources.¹³ Recognising a need to improve STI surveillance in Aotearoa New Zealand, the Health (Protection) Amendment Act 2016 saw syphilis and gonorrhoea designated notifiable diseases.¹⁴ This introduced the legal requirement for diagnosing clinicians to complete an anonymous case report form to provide behavioural, clinical and management information for gonorrhoea and syphilis cases. Laboratory notification is also required for gonorrhoea (but not syphilis).¹⁵ The clinician-notification system was rolled out in late 2018, but no data have so far been published related to contact tracing. This paper reports on aggregated data for gonorrhoea and syphilis cases notified via clinician reporting in 2019.

Aggregated data were requested from the Institute of Environmental Science and Research (ESR) in November 2021 for clinician-notified gonorrhoea and syphilis cases in 2019. Notification data from 2019 were requested due to the impact of coronavirus disease 2019 (COVID-19) on behavioural patterns, access to health care and availability of testing in 2020.¹⁶ We received clinician-completed case report numbers and laboratory notification numbers by District Health Board (DHB); treatment status; numbers of partners in the past 3 months provided by sexual behaviour (reported by ESR as ‘MSM’ men who have sex with men, ‘MSW’ men who have sex with women and ‘WSM’ women who have sex with men); probable source of infection (casual partner, regular partner, client (if sex worker), sex worker, unknown); and contact tracing status (recorded as ‘already initiated or plan to undertake’, ‘already referred to another service for contact tracing’ or ‘incomplete due to anonymous contacts’).

To assess potential contact tracing volumes, total numbers of partners per case (by sexual behaviour) were estimated for each STI by taking the midpoint of each category supplied (ie for 64 MSM with 5–9 partners, we used 7 as the total number of partners and multiplied that by 64). The estimated number of contacts for those with ≥15 partners was set at 18. This analysis was part of a broader study on contact tracing undertaken for the lead author’s Master of Public Health dissertation. Ethical approval was granted by the University of Otago Human Ethics Committee (Category B, Ref. D21/313, approved 14 October 2021).

Clinician-notification of gonorrhoea cases in 2019 was incomplete, with only 43.6% (3138/7200) of laboratory-notified cases reported by a clinician. The percentage of clinician-notified cases varied across regions, ranging from 10.0 to 61.5% (see Supplementary Table S2 for notifications by DHB region).

Table 1 presents information documented in clinician-notification forms related to case management and contact tracing for 3138 gonorrhoea cases and 722 syphilis cases notified in 2019. Males made up 52.3% of all notified gonorrhoea cases and 82.7% of syphilis cases. Although clinicians indicated that contact tracing had been ‘initiated or was planned’ for around 80% of gonorrhoea and syphilis cases, there was no way to distinguish between these two options. Casual partners were the most commonly reported probable source of infection for both STIs.

Table 1.  Information documented about clinician-notified gonorrhoea and syphilis cases reported in 2019.

Fig. 1 depicts the estimated volume of contact tracing required for gonorrhoea and syphilis cases based on the estimated number of contacts per case. Extrapolating this out to cases with other and unknown sexual behaviour and all laboratory-notified gonorrhoea cases, we estimate there would be at least 28 080 contacts of gonorrhoea cases (7200 cases with an average of 3.9 contacts). For the 722 cases of syphilis (with an average of 3.8 contacts), an estimated 2744 contacts would require contact tracing.

Fig. 1.  Estimated volume of contact tracing required for gonorrhoea and syphilis based on reported number of contacts of cases with known sexual behaviour in 2019.

There was widespread under-reporting of gonorrhoea cases by clinicians in all DHBs, which suggests low levels of buy-in to the notification process. Incomplete surveillance data for notifiable STIs mean there is only partial data on behavioural characteristics and contact tracing status for individuals diagnosed with gonorrhoea and syphilis. We estimated over 30 000 contacts of cases of gonorrhoea and syphilis diagnosed in 2019 would require contact tracing. Although not all contacts would be reachable, this is a sizeable workload that needs to be factored into clinical case management.

In the last two reported years clinician-notification rates for gonorrhoea have improved slightly to 49% of laboratory-notified cases in 2020 and 56% of cases in 2021.^17,18 ESR suggest that syphilis is under-reported to the same degree as gonorrhoea,¹⁷ which is particularly concerning because syphilis relies solely on clinician notification. Accurate surveillance data that quantify incidence, location and case characteristics are needed to inform policy and interventions designed to reduce transmission.

The barriers and frustrations facing clinicians engaging with the notification system have previously been reported, with the five pages of information required deemed to exceed what is necessary, and an argument made to prioritise useful over interesting data.¹⁹ ESR acknowledge that ‘long complex case report forms with multiple manual steps for access and data entry are a significant issue for clinicians and for the quality of surveillance data’.¹⁷ Making clear to diagnosing clinicians how the information they provide will be acted on would also be beneficial. Revising forms to collect only the most pertinent information, and information that is needed for a clear purpose should be prioritised. For example, asking whether contact tracing ‘has been initiated or planned’ provides little useful information without distinguishing between these options, and it is just the first step in a process that involves eliciting information about, informing, testing and treating sexual contacts.²⁰

The surveillance data indicated that contact tracing was initiated or planned for >80% of cases. This is consistent with primary care research in Aotearoa New Zealand where documentation of contact tracing discussion occurred for 74% of gonorrhoea and chlamydia cases,⁴ but only 22% of cases had documentation that partners were informed and 9% that partners were tested.⁴ Based on a review of international evidence, it has been argued that contact tracing outcomes should be measured at each stage of the process and separately documented for regular and casual contacts.²⁰ It is recommended that these outcomes are used to inform standards to guide practice.²⁰ Aotearoa New Zealand needs to consider whether to develop auditable standards for STI contact tracing and within that, consider what role (if any) clinician notification has in the collection of such data.

In this study, people with gonorrhoea and syphilis thought that the most probable source of infection was from casual partners. International research suggests that people feel a greater sense of responsibility and are more likely to notify a regular than a casual partner, and more likely to want providers to notify casual partners on their behalf.³ If providers do not have the capacity, processes or tools in place to notify casual partners, this represents a significant volume of unchecked infection in the community. Furthermore, around one in five cases of syphilis and one in six cases of gonorrhoea had anonymous contacts that prohibited contact tracing. This underscores the importance of having health promotion strategies, and easily accessible services that reach higher-risk populations for screening.

Notification data from ESR were provided in aggregate form to preserve the anonymity of cases, and due to the time constraints of the research. This limited our ability to describe contact tracing data in detail (eg in relation to demographic characteristics of cases or by region). Our estimates of total contact tracing volumes assumed partner numbers would be similar for notified and un-notified cases, which may not be true. Reasons for differences in reporting rates by DHB were not sought as part of this study, but warrant further exploration, particularly as ESR report that cases for Māori and Pacific people are underrepresented in clinician-notification data.¹⁷

Although surveillance data for gonorrhoea and syphilis are incomplete, estimates can be obtained about the number and type of contacts, which can be used to inform contact tracing strategies. Optimisation of the content of clinician-completed forms and an improved response rate would provide a more complete picture to inform interventions to address the high and inequitable prevalence of STIs in Aotearoa New Zealand.

Supplementary material is available online.

The data presented here were obtained in aggregate form from ESR. Data will be shared upon reasonable request to the corresponding author, with permission from ESR.

The authors have no conflicts of interest to declare.

The lead author received a training stipend from the New Zealand College of Public Health Medicine during her Masters of Public Health.