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Analysis of the Effectiveness of Surveillance and Containment…


On March 13, 2020, this report was posted on-line as an MMWR Early Launch.

Yixiang Ng, MSc1*; Zongbin Li, MBBS1*; Yi Xian Chua, MSc1; Wei Liang Chaw, MSc1; Zheng Zhao, MSc1; Benjamin Er, MSc1; Rachael Pung, MSc1; Calvin J. Chiew, MPH1; David C. Lye, MBBS2,3,4,5; Derrick Heng, MPH1; Vernon J. Lee, PhD1,6* (View writer affiliations)

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Abstract

What’s already identified about this subject?

First detected in China in late 2019, coronavirus illness 2019 (COVID-19) transmission has unfold globally.

What’s added by this report?

Singapore applied a multipronged surveillance and containment technique that contributed to enhanced case ascertainment and slowing of the outbreak. Based mostly on evaluation of the primary 100 instances, the imply interval from symptom onset to isolation was 5.6 days and declined after roughly 1 month.

What are the implications for public well being follow?

A multipronged surveillance technique may result in enhanced case detection and lowered transmission of extremely infectious illnesses comparable to COVID-19.

Coronavirus illness 2019 (COVID-19) was first reported in Wuhan, China, in December 2019, and has since unfold globally, leading to >95,000 confirmed COVID-19 instances worldwide by March 5, 2020 (1). Singapore adopted a multipronged surveillance technique that included making use of the case definition at medical consults, tracing contacts of sufferers with laboratory-confirmed COVID-19, enhancing surveillance amongst completely different affected person teams (all sufferers with pneumonia, hospitalized sufferers in intensive care models [ICUs] with attainable infectious illnesses, main care sufferers with influenza-like sickness, and deaths from attainable infectious etiologies), and permitting clinician discretion (i.e., choice to order a check based mostly on scientific suspicion, even when the case definition was not met) to establish COVID-19 sufferers. Containment measures, together with affected person isolation and quarantine, energetic monitoring of contacts, border controls, and group training and precautions, had been carried out to attenuate illness unfold. As of March 5, 2020, a complete of 117 COVID-19 instances had been recognized in Singapore. This report analyzes the primary 100 COVID-19 sufferers in Singapore to find out the effectiveness of the surveillance and containment measures. COVID-19 sufferers had been categorized by the first means by which they had been detected. Software of the case definition and speak to tracing recognized 73 sufferers, 16 had been detected by enhanced surveillance, and 11 had been recognized by laboratory testing based mostly on suppliers’ scientific discretion. Effectiveness of those measures was assessed by calculating the 7-day transferring common of the interval from symptom onset to isolation in hospital or quarantine, which indicated important lowering tendencies for each native and imported COVID-19 instances. Fast identification and isolation of instances, quarantine of shut contacts, and energetic monitoring of different contacts have been efficient in suppressing growth of the outbreak and have implications for different nations experiencing outbreaks.

On January 2, 2020, days after the primary report of the illness from China, the ministry of well being (MOH) in Singapore, a small island city-state in Southeast Asia with a inhabitants of roughly 5.7 million, developed an area case definition (Supplementary Desk, https://stacks.cdc.gov/view/cdc/85735) and suggested all medical practitioners to be vigilant for suspected COVID-19 sufferers (2). A confirmed case was outlined as a constructive check for SARS-CoV-2, the virus that causes COVID-19, by reverse transcription–polymerase chain response (RT-PCR) (3), or a constructive viral microneutralization antibody check utilizing a SARS-CoV-2 virus isolate (BetaCoV/Singapore/2/2020; GISAID accession 76 quantity EPI_ISL_407987) and performed utilizing beforehand revealed protocols (4). At hospitals, sufferers with suspected COVID-19 obtained chest radiographs and RT-PCR testing on no less than two nasopharyngeal swabs collected 24 hours aside (5). Physicians are mandated to report all suspected and confirmed COVID-19 sufferers via a centralized illness notification system.

The case definition was up to date 5 instances following the outbreak’s begin to adapt to the evolving world state of affairs (Supplementary Desk, https://stacks.cdc.gov/view/cdc/85735). The MOH carried out contact tracing round confirmed instances to establish individuals who might need been contaminated. Contacts with fever (temperature ≥100.4°F [≥38°C]) or respiratory signs had been transferred on to a hospital for additional analysis and testing. Shut contacts had been outlined as having shut (inside 6.6 ft [2 m]) and extended (typically ≥half-hour) contact with the COVID-19 affected person. Contacts at decrease danger had been individuals who had some interactions with the COVID-19 affected person for shorter intervals of time. Asymptomatic shut contacts had been positioned underneath obligatory quarantine for 14 days, and contacts at decrease danger had been positioned underneath energetic monitoring. All contacts had been assessed by phone for fever or respiratory signs by public well being officers through the quarantine or monitoring interval, thrice day by day for shut contacts and as soon as day by day for contacts at decrease danger. Contacts who grew to become symptomatic had been transferred to a hospital. Surveillance was enhanced in late January 2020 by testing the next teams for COVID-19: 1) all hospitalized sufferers with pneumonia (later expanded to incorporate sufferers with pneumonia evaluated in main care settings); 2) ICU sufferers with attainable infectious causes as decided by the doctor; 3) sufferers with influenza-like sickness at sentinel authorities and personal main care clinics included within the routine influenza surveillance community; and 4) deaths from attainable infectious causes. As well as, medical practitioners may select to check sufferers if there was scientific (e.g., extended respiratory sickness with unknown trigger) or epidemiologic (e.g., affiliation with identified clusters) suspicion.

The effectiveness of Singapore’s surveillance and containment efforts was assessed from the outbreak’s begin till February 29 by calculating the 7-day transferring common of the interval from symptom onset to isolation in hospital or quarantine. This measure gives a sign of the time spent throughout the group when an individual with COVID-19 is doubtlessly infectious. Variations within the percentages of instances detected via the completely different surveillance parts had been examined utilizing the chi-squared or Fisher’s actual check. All analyses had been performed utilizing R statistical software program (model 3.5.1; The R Basis).

Among the many first 100 confirmed COVID-19 instances in Singapore, the common affected person age was 42.5 years (median = 41 years; interquartile vary [IQR] = 34–54 years) (Desk). The bulk (72%) of sufferers had been aged 30–59 years, and 60% of sufferers had been male. RT-PCR confirmed 99% of instances, and one case was confirmed by viral microneutralization testing. Twenty-four instances had been imported, and the remaining resulted from native transmission. Fifteen sufferers had been ever within the ICU; no deaths have been reported thus far. Contact tracing contributed to the first detection of roughly half (53%) of COVID-19 sufferers. One other 20 (20%) sufferers had been recognized at normal practitioner clinics or hospitals as a result of they met the case definition; 16 had been recognized via enhanced surveillance (15 from pneumonia surveillance and one from the ICU), and one other 11 via medical suppliers’ scientific discretion. No sufferers had been recognized via surveillance for influenza-like sickness. A big distinction was discovered within the proportion of instances detected by the assorted surveillance strategies, relying on whether or not the instances had been linked to a different COVID-19 affected person or by journey to China, in contrast with instances that might not be linked to a different case (p<0.001). Amongst linked instances, the most important proportion (62.7%) was detected via contact tracing, whereas amongst unlinked instances, the most important proportion of instances (58.8%) was detected via enhanced surveillance (Desk). The earliest symptom onset date reported by a COVID-19 affected person was January 14 (Determine 1). The epidemic curve peaked on January 30, when 9 sufferers had been recognized, earlier than declining to 2 to 5 sufferers per day on February 11 and persevering with ahead. Worldwide importations accounted for a majority of instances on the outbreak’s begin earlier than extra native instances had been detected. The imply interval from symptom onset to hospital isolation or quarantine was 5.6 days (median = 5 days; IQR = 2–8 days). The 7-day transferring common of the interval from symptom onset to isolation declined considerably throughout the examine interval for each imported and native instances, from 9.0 and 18.0 days to 0.9 and three.1 days, respectively (p<0.001) (Determine 2). Among the many 53 sufferers first recognized via contact tracing, 13 (24.5%) had been contacted on or earlier than the date of symptom onset.

Dialogue

On this evaluation of the measures that Singapore, a small city-state, put in place to establish COVID-19 sufferers and comprise illness unfold within the early outbreak section, roughly one quarter of instances had been detected via enhanced surveillance amongst hospitalized sufferers with pneumonia and ICU sufferers (16 instances [16%]) and thru suppliers’ scientific discretion (11 [11%]). A latest examine thought of Singapore to have the best surveillance capability for COVID-19 amongst all nations (6). The examine estimated that if different nations had comparable detection capacities as Singapore, the worldwide variety of imported instances detected can be 2.8 instances increased than the noticed present quantity. The surveillance strategies in Singapore complemented each other to establish contaminated individuals, with the overlapping parts constituting security nets; not one of the strategies alone would have detected all sufferers. The case definition was essential for clinicians to make use of as a basis, and energetic case discovering round COVID-19 sufferers via contact tracing was helpful in detecting new sufferers early for isolation.

The improved surveillance measures of SARS-CoV-2 testing of all sufferers with pneumonia, surveillance of ICU sufferers with extreme sickness and deaths doubtlessly attributable to COVID-19, and scientific discretion in requesting testing had been all essential in detecting initially unlinked sufferers for additional investigation. Adoption of a number of surveillance mechanisms can guarantee broad protection as a result of every missed case can result in chains of transmission that is likely to be tough to comprise subsequently.

Singapore has applied aggressive measures to comprise native transmission of COVID-19. After an preliminary improve in domestically transmitted instances, the variety of newly recognized instances decreased after roughly 1 month, decided by symptom onset dates. This lower is probably going a results of the early implementation of surveillance and detection measures whereas the numbers of sufferers had been nonetheless small and individual-level containment was attainable; a bigger variety of instances would have pushed group transmission. The decline within the 7-day transferring common of interval from onset to isolation in hospital and quarantine was additionally indicative of efforts to comprise illness unfold throughout time.

Singapore has additionally applied different measures to scale back the unfold of COVID-19. To forestall imported instances from seeding native transmission, border management measures included temperature screening initially for vacationers on flights from Wuhan earlier than increasing to incorporate all vacationers getting into Singapore at air, sea, and land checkpoints (7). Quick-term guests with journey previously 14 days to chose nations or areas (initially mainland China and later expanded to South Korea, northern Italy, and Iran) had been denied entry; Singapore residents coming back from these areas had been positioned underneath a compulsory 14-day self-quarantine. To scale back group unfold, public training messages had been targeted on private hygiene and in search of early medical care and self-isolation when having respiratory signs. As of March 5, 2020, faculties haven’t closed as a result of there was no widespread group transmission in Singapore and few instances amongst kids; precautionary measures comparable to decreasing mixing throughout lessons or faculties have been applied to restrict attainable illness transmission.

The findings on this report are topic to no less than three limitations. First, the 7-day transferring common interval from symptom onset to isolation may fluctuate for latest dates as further sufferers are detected and is likely to be inadequate as a single measure to judge the effectiveness of containment. Additional indicators to evaluate effectiveness of containment measures must be investigated. However, the downward pattern was important from the outbreak’s begin till early February. Second, the case detection strategies had been primarily targeted on symptomatic sufferers. Additional research are wanted to evaluate the variety of asymptomatic sufferers in the neighborhood and their potential to transmit illness and whether or not further measures focusing on asymptomatic sufferers would have resulted in additional case reductions. Lastly, generalizability of outcomes is proscribed due to the small pattern dimension and lack of instances in settings comparable to long-term nursing amenities and well being care settings.

Singapore applied sturdy surveillance and containment measures, which seem to have slowed the expansion of the outbreak. These measures is likely to be helpful for detection and containment of COVID-19 in different nations which might be experiencing the beginning of native COVID-19 outbreaks. Singapore is a small island city-state, and nations with different traits would possibly must adapt and increase Singapore’s approaches to realize the identical stage of effectiveness.


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