Newly released data from ESR shows the number of reported cases of syphilis, gonorrhoea and chlamydia dropped in the first half of 2020.
ESR publishes an STI dashboard(external link), which provides information on trends in syphilis, gonorrhoea and chlamydia in New Zealand. This dashboard has now been updated to include data up to June 30, 2020.
ESR Public Health Physician Dr Gerard Sonder says that while a reduction in sexually transmitted infections (STIs) reported is always encouraging, results need to be interpreted in the context of COVID-19 restrictions.
“While we have seen a reduction in diagnoses for syphilis, gonorrhoea and chlamydia, it doesn’t necessarily mean a reduction of the STI’s in the community. The COVID-19 pandemic caused a highly unusual, rapid change in the epidemiology of many infectious diseases, including STIs, but a drop may be misleading.
“And while New Zealand experienced unprecedented changes to social behaviour over this time, we also saw changes in the availability of testing, health-seeking behaviour and access to health care. As we see future releases of this dashboard in the coming months, we may see more accurate trends as testing and behaviours normalise,” he says.
Dr Sonder says that although there has been an overall decrease in diagnoses, Māori and Pacific peoples continue to have much higher rates of disease.
“In some cases, three times more than other ethnic groups”.
The majority of cases reported in Māori and Pacific peoples were in people aged 15-29 years.
There were 589 cases of infectious syphilis in the 12 months ended 30 June 2020.
Dr Sonder says the reduction in syphilis cases appears to fit with the overall trends from 2019, where case numbers had begun to level-off.
“Unlike for chlamydia and gonorrhoea, syphilis testing and reporting was less affected by COVID-19 restrictions.
“The historical trends show reported cases of syphilis steadily increased from 2013 until mid-2019 when notifications started to level off. So, the continued decline in syphilis incidence is consistent with what was happening prior to COVID-19,” Dr Sonder says.
Most cases of syphilis continue to be reported in males aged 20–39 years and the majority report being European/other ethnicity. Most reported cases are from large cities, with cases reporting European ethnicity decreasing noticeably over the past 12 months.
The proportion of cases reporting MSM behaviour has steadily decreased from 85 per cent in 2014 to 61 per cent in 2020; this is compared to 14 per cent reporting heterosexual behaviour in 2014, increasing to 34 per cent in 2020.
- 722 cases in the 12 months ended 31 December 2019
- 643 cases in the 12 months ended 31 March 2020.
The number of congenital syphilis cases reported (confirmed and probable) were one in 2016, four in 2017, four in 2018 (one additional case under investigation), five in 2019, and one in the first half of 2020.
There were 576 cases of chlamydia per 100,000 of the New Zealand population reported for the 12 months ended 30 June 2020.
Dr Sonder says Chlamydia is the most commonly reported STI in New Zealand and rates have been relatively stable since 2013.
“Although, as a result of limited testing and access to health care during COVID-19, rates decreased in early 2020. The demand for laboratory resources for COVID-19 testing meant testing for chlamydia was restricted from late-March in most district health boards around the country.”
The highest chlamydia rate was reported in females aged 15−29 years but there has been an increasing trend in the rate in males since the end of 2017. Dr Sonder says the continuing lower rate in males could be due at least in part to lower testing rates in males, suggesting that many infections in males remain undiagnosed and untreated.
- 662 cases per 100,000 of the New Zealand population reported for the 12 months ended 31 December 2019
- 645 cases per 100,000 of the New Zealand population reported for the 12 months ended 31 March 2020.
There were 146 cases of gonorrhoea per 100,000 of the New Zealand population reported for the 12 months ended 30 June 2020.
Gonorrhoea rates were increasing through 2019, and rates remained stable before a larger decrease in the first half of 2020. However, like chlamydia, testing for gonorrhoea was restricted during lockdown.
Dr Sonder says you can see a clear example of the way COVID-19 restrictions may have affected the data by looking at the number of notifications for gonorrhoea per month.
“In January and February 2020, notifications were more than a quarter higher compared to January and February 2019. In April and May 2020, after testing restrictions were implemented for asymptomatic gonorrhoea, and chlamydia, and alert level changes altered clinical and social interactions, testing rates dropped and notifications decreased below the levels seen in the same months of 2019.”
The highest rates for gonorrhoea continue to be reported in males, and people aged 20–29 years. Māori and Pacific peoples continue to have much higher rates of the disease compared with other ethnic groups.
- 146 cases per 100,000 of the New Zealand population reported for the 12 months ended 31 December 2019
- 152 cases per 100,000 of the New Zealand population reported for the 12 months ended 31 March 2020.
The remainder of 2020’s data is to be analysed and released later in the year.
How STI surveillance works in New Zealand
ESR operates the following surveillance systems for gonorrhoea, chlamydia and syphilis:
- For gonorrhoea and chlamydia, a laboratory-based surveillance system is in place whereby all laboratory results for gonorrhoea and chlamydia are sent to ESR along with demographic information (age, sex, ethnicity and geographic region). For gonorrhoea, there is also an online clinician notification system in place to collect additional information for cases including risk factor information such as sexual behaviour.
- For syphilis, there is a clinician notification system in place to collect demographic, laboratory and risk factor information.
The Dashboard utilises quarterly rolling 12-month case counts (rates per 100,000) which provide insight into slow-moving trends. For this reason, COVID-19 restrictions may also affect subsequent dashboard releases for the next 12 months. Further interpretation of this data in the context of COVID-19 has been provided in addition to the dashboard – please click here to read this(external link).