East Asia and the Pacific Surveillance Metrics and History of the COVID-19 Pandemic: Updated Epidemiological Assessment (Preprint)

Abstract

This study updates the COVID-19 pandemic surveillance in East Asia and the Pacific we first conducted in 2020 with two additional years of data for the region.

First, we measure whether there was an expansion or contraction of the pandemic in East Asia and the Pacific region when the World Health Organization (WHO) declared the end of the COVID-19 public health emergency of international concern on May 5, 2023. Second, we use dynamic and genomic surveillance methods to describe the dynamic history of the pandemic in the region and situate the window of the WHO declaration within the broader history. Third, we provide historical context for the course of the pandemic in East Asia and the Pacific.

In addition to updates of traditional surveillance data and dynamic panel estimates from the original study Post et al. (2021), this study used data on sequenced SARS-CoV-2 variants from the Global Initiative on Sharing All Influenza Data (GISAID) to identify the appearance and duration of variants of concern. We used Nextclade nomenclature to collect clade designations from sequences and Pangolin nomenclature for lineage designations of SARS-CoV-2. Finally, we conducted a one-sided t-test for whether regional weekly speed was greater than an outbreak threshold of ten. We ran the test iteratively with six months of data across the sample period.

For the week of April 28, Brunei had by far the highest rate of new COVID-19 cases at 1,431 per 100K population with New Zealand at 204, Australia at 115, and South Korea at 31. These rates exceeded the outbreak threshold according to the CDC. However, all other countries and territories in the region were well below the outbreak threshold, and the regional transmission rate was below 10 cases per 100K population. Since the end of January 2023, the region has not been in a state of outbreak.

While COVID-19 continues to circulate in East Asia and the Pacific, transmission rates had fallen below outbreak status by the time of the WHO declaration. Compared to other global regions, East Asia and the Pacific had the latest outbreaks driven by the Omicron variant. COVID-19 appears to be endemic in the region, no longer reaching the threshold of the pandemic definition. However, the late outbreaks raise uncertainty about whether the pandemic was truly over for the region at the time of the WHO declaration.