Defining the peak: Point prevalence of SARS-CoV-2 using randomised sampling

Area of Science:

• Public Health
• Epidemiology
• Virology

Background:

• Queensland experienced a significant increase in Coronavirus disease 2019 (COVID-19) cases following eased border restrictions in December 2021.
• The SARS-CoV-2 Omicron variant became the predominant strain, leading to challenges in community testing accessibility due to rapid case escalation.
• Accurate community prevalence data is crucial for effective public health responses to highly transmissible diseases.

Purpose of the Study:

• To estimate the point prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in the Gold Coast community.
• To monitor the trend of COVID-19 prevalence following a surge in cases.
• To assess the utility of a modified randomized household cluster survey for infectious disease surveillance.

Main Methods:

• A modified randomized household cluster survey was implemented on the Gold Coast.
• Polymerase chain reaction (PCR) testing on self-collected swabs was used to detect SARS-CoV-2.
• Surveillance was conducted over five weeks, with three visits to households to estimate point prevalence.

Main Results:

• The estimated point prevalence of SARS-CoV-2 by PCR was 17.2% on January 22, 2022.
• Prevalence decreased significantly to 5.2% by February 5, 2022, and further to 1.1% by February 19, 2022.
• Of 1,379 specimens tested, 63 were positive for SARS-CoV-2, and all sequenced variants (35) were Omicron (B.1.1.529).

Conclusions:

• The implemented surveillance program effectively estimated and tracked COVID-19 prevalence in the Gold Coast community.
• The findings highlight the rapid rise and subsequent fall of the Omicron variant wave.
• The methodology is scalable and reproducible for surveillance in other jurisdictions.