In the initial phases of the COVID-19 pandemic, Singapore received international recognition for her outbreak response and was regarded as the “gold standard” by international researchers . The situation has evolved markedly since. By April 2020, rapid transmission amongst the migrant workers residing in dormitories led to a sudden surge in the number of cases. This vulnerable sector presented a fresh set of challenges to our healthcare system.
Similar to Singapore, migrant workers form a significant proportion of the workforce for many countries across the world, including those in North America, Europe, and parts of Asia . Other vulnerable sectors include highly populated, closely packed urban residential areas and incarcerated populations such as prison facilities or even refugees living in overcrowded detention camps [3, 4]. A previous review of infectious diseases amongst migrant workers in Singapore had highlighted the significantly higher risk of transmission of communicable diseases within this vulnerable group, underlining the unique challenge of curbing transmission in crowded living conditions .
This paper aims to describe the key adaptations in workflow  in the National Centre for Infectious Diseases (NCID) Screening Centre (SC) and Tan Tock Seng Hospital (TTSH) Emergency Department (ED), respectively, in response to the evolving challenges encountered in the COVID-19 pandemic.
The first wave (January to March 2020)
Incorporating her previous experiences combating the 2003 severe acute respiratory syndrome coronavirus (SARS-CoV) outbreak , Singapore adopted a rigorous containment strategy involving aggressive swab testing, rapid contact tracing and quarantine of positive cases and close contacts.
One of the important keys to Singapore’s containment efforts has been the SC which has been fully operational since 31 January 2020 and housed in NCID, a purpose-built facility which opened in September 2019, dedicated to the containment of infectious disease outbreaks . NCID is located adjacent to its partnering hospital, TTSH. Emergency physicians from TTSH, in close collaboration with their colleagues from the Infectious Diseases Department, helm operations at both the SC and the adjacent Emergency Department. To sustain round the clock operations, a “Whole-of-Hospital” approach was adopted with and assistance of doctors from the other departments including General Surgery, Orthopedic Surgery, Hand Surgery, Neurosurgery, Radiology, Pathology, Ophthalmology, Otorhinolaryngology and Urology who took up roles as medical officers in the SC. Nursing and administrative staff were also recruited from the different departments and clinics.
The initial efficacy of Singapore’s containment strategies has been demonstrated in a recent study which analysed the first 100 positive cases of COVID-19 in Singapore (up to 29 February 2020) . The 7-day moving average of the interval from symptom onset to isolation during the 1-month study period declined significantly for both imported and local cases, from 9.0 and 18.0 days to 0.9 and 3.1 days.
The second wave (April 2020 to present)
By April 2020, the situation had evolved in 3 main ways (see Fig. 1). Firstly, the number of imported cases started to decline from its peak of 48 cases. Secondly, there was a gradual climb in the number of community cases, with a peak of 58 cases on 8 April 2020. This included an average of more than 10 unlinked cases a day. Finally, there was a sharp rise in positive cases amongst the migrant worker population with a peak of 1371 cases on 20 April 2020.