Dear Editor,
Li et al. reported health care worker (HCW) deaths from coronavirus disease (COVID-19) (1). HCWs are at risk of COVID-19 from nosocomial transmission and community acquisitions (2). Since the first imported case of COVID-19 from Wuhan, China, on January 23, 2020, the number of locally acquired COVID-19 cases has increased in Singapore. To break the chain of disease transmission, Singapore implemented the ‘Circuit Breaker’ measures between April 07, 2020 and June 01, 2020 (3). The measures included the closure of non-essential workplaces and schools, suspension of religious activities, movement restrictions, mandatory use of face masks in public areas, and safe distancing measures (3). Since the lifting of the measures on June 02, 2020, hospitals have resumed non-COVID-19-related clinical services including clinically-indicated elective surgeries and chronic disease clinics. Furthermore, with the gradual resumption of economic activities and essential travel, an increase in the community transmission of COVID-19 can be expected.
Early identification of COVID-19-infected HCWs can detect viral transmission, determine the effectiveness of control measures, and prevent onward transmission to patients and co-workers in healthcare settings (1,4,5). At the 1600-bed Tan Tock Seng Hospital (TTSH) and its co-located 330-bed National Centre for Infectious Disease (NCID), the designated center for emerging infectious disease outbreaks including COVID-19, a comprehensive staff sickness surveillance system has been implemented for >10,000 HCWs (6). The system initially comprised an online temperature and sickness reporting platform and medical screening for COVID-19 in unwell HCWs working in COVID-19-related work areas at the TTSH's Emergency Department or NCID's COVID-19 Screening Center (SC). In preparation for the easing of “Circuit Breaker” measures, the HCW sickness surveillance system was enhanced to include SARS-CoV-2 swab testing for all HCWs with fever or symptoms of acute respiratory infection (ARI) from May 06, 2020 regardless of exposure risk. In addition to NCID's SC, TTSH's Occupational Health Clinic (OHC) also performed SARS-CoV-2 swab testing for all HCWs with fever or ARI symptoms. HCWs who had attended a primary care clinic near their homes were required to be tested for SARS-CoV-2 either at the clinic or the OHC. We compare the epidemiology of sick HCWs and describe the effectiveness of the enhanced HCW ARI surveillance program in COVID-19 detection, in the last month of the “Circuit Breaker” and the first month after the lifting of the “Circuit Breaker”.
We present data from May 06, 2020 to June 30, 2020 corresponding to the 4 weeks before (period A) and after (period B) the lifting of the ‘Circuit Breaker’ on June 02, 2020. A total of 997 sickness episodes from 874 HCWs (434 in period A and 440 in period B) were included (Figure 1 ). The median age was 31 (IQR: 27-38) years, 176 (20.1%) were male, 206 (23.6%) had worked in COVID-19-related work areas and 104 (11.9%) had more than 1 illness episode. Among the 617 (70.6%) HCWs who attended at TTSH's OHC and NCID's SC, a significantly higher proportion of unwell HCWs in period A had served in COVID-19-related work areas compared to period B (127 [29.3%] vs 79 [18.0%], P<0.001). The median time from symptom onset to presentation for care was 1 day (IQR 1-3). All 874 HCWs were screened for SARS-CoV-2 by polymerase chain reaction (PCR), and none was detected with COVID-19. Additionally, HCWs who medically attended at the OHC (n=288) were tested for Adenovirus, Coronaviruses (229E, HKU1, NL63 and OC43), Respiratory Syncytial Virus, Influenza A (H1, H1-2009 and H3), Influenza B, Parainfluenza (1,2,3,4), Human Rhinovirus, Human Enterovirus, Human Metapneumovirus, Bordetella pertussis and parapertussis, Chlamydia pneumoniae, and Mycoplasma pneumoniae with the BioFire® FilmArray® Respiratory panel. Only Adenovirus was detected in 1 HCW and during period B (Table 1 ).
Figure 1.
Weekly incidence rate of acute respiratory illness (ARI) per 1000 staff and number of ARI episodes by staff categories from May 06, 2020 to June 30, 2020. The ‘Circuit Breaker’ ended on June 01, 2020.
Table 1.
Incidence of weekly acute respiratory illness (ARI) episodes and characteristics of healthcare workers (HCWs) with ARI detected by the surveillance programme between May 06, 2020 and June 30, 2020.
| Incidence of HCW illness episodes | Totala (n=997) | Period Ab (n=495) | Period Bb (n=502) | P-value |
|---|---|---|---|---|
| Weekly average | 125 | - | - | |
| Week starting: | ||||
| May 06, 2020 | 140 | 140 | - | |
| May 13, 2020 | 154 | 154 | - | |
| May 20, 2020 | 107 | 107 | - | |
| May 27, 2020 | 114 | 94 | 20 | |
| June 03, 2020 | 138 | - | 138 | |
| June 10, 2020 | 132 | - | 132 | |
| June 17, 2020 | 88 | - | 88 | |
| June 24, 2020 | 124 | - | 124 | |
| Demographics of HCWs with ARI | Totala (n=874) | Period Ab (n=434) | Period Bb (n=440) | P-value |
|---|---|---|---|---|
| Age (years) | ||||
| Mean ± SD | 34 ± 11 | 33 ± 10 | 35 ± 11 | 0.053 |
| Median(IQR) | 31 (27-38) | 31 (27-37) | 31 (27-40) | 0.282 |
| Range | 19-74 | 19-69 | 19-74 | |
| Gender | ||||
| Male | 176 (20.1%) | 82 (18.9%) | 94 (21.4%) | 0.363 |
| Staff Category | 0.491 | |||
| Nursing | 347 (39.7%) | 178 (41.0%) | 169 (38.4%) | |
| Administration and Ancillary | 320 (36.6%) | 148 (34.1%) | 172 (39.1%) | |
| Allied Health and Pharmacy | 133 (15.2%) | 70 (16.1%) | 63 (14.3%) | |
| Medical | 74 (8.5%) | 38 (8.8%) | 36 (8.2%) | |
| COVID19-exposure factors | <0.001 | |||
| Serve in COVID-19 areac | 206 (23.6%) | 127 (29.3%) | 79 (18.0%) | |
| Serve in non-COVID-19 area with known in-hospital contact with a confirmed cased | 33 (3.8%) | 12 (2.8%) | 21 (4.8%) | |
| Serve in non-COVID-19 area with no known in-hospital contact with a confirmed case | 635 (72.7%) | 295 (68.0%) | 340 (77.3%) | |
| Number of illness episodes | ||||
| 1 | 770 (88.1%) | - | - | |
| 2 | 93 (10.6%) | - | - | |
| ≥3 | 11 (1.3%) | - | - | |
| Charlson's Comorbidity Index | 0.020 | |||
| 0 | 554 (89.8%) | 305 (92.4%) | 249 (86.8%) | |
| ≥ 1 | 63 (10.2%) | 25 (7.6%) | 38 (13.2%) | |
| Co-morbidities | ||||
| Asthma | 42 (6.8%) | 16 (4.9%) | 26 (9.1%) | 0.038 |
| Hypertension | 32 (5.2%) | 14 (4.2%) | 18 (6.3%) | 0.257 |
| Diabetes Mellitus | 15 (2.4%) | 4 (1.2%) | 11 (3.8%) | 0.035 |
| Day of illness on presentation – median (IQR) | 1 (1, 2, 3) | 1 (1, 2, 3) | 1 (0-2) | 0.002 |
| Presenting Symptoms | ||||
| Sore throat | 311 (50.4%) | 171 (51.8%) | 140 (48.8%) | 0.452 |
| Cough | 274 (44.4%) | 154 (46.7%) | 120 (41.8%) | 0.226 |
| Rhinorrhoea | 228 (37.0%) | 127 (38.5%) | 101 (35.2%) | 0.398 |
| Fever | 223 (36.1%) | 116 (35.2%) | 107 (37.3%) | 0.583 |
| Headache | 65 (10.5%) | 36 (10.9%) | 29 (10.1%) | 0.745 |
| Myalgia | 76 (12.3%) | 31 (9.4%) | 45 (15.7%) | 0.018 |
| Diarrhoea | 59 (9.6%) | 29 (8.8%) | 30 (10.5%) | 0.483 |
| Respiratory virus detected | ||||
| SARS-CoV-2 | 0 | 0 | 0 | |
| Adenovirus | 1 | 0 | 1 |
a Values are indicated in no. (%) unless otherwise stated.
b Period A refers to the period from May 06, 2020 to June 01, 2020; Period B refers to the period from June 02, 2020 to June 30, 2020.
c HCWs working in COVID-19 designated clinical areas such as screening centre, emergency department, wards, or laboratory where COVID-19 specimens were handled.
d HCWs working in non-COVID-19 areas exposed to patients initially not suspected to have COVID-19 and not admitted to COVID-19 designated clinical areas but who were eventually confirmed with COVID-19.
e HCWs who medically attended at TTSH's OHC or NCID's SC.
In spite of the enhanced surveillance, no HCW was identified with SARS-COV-2 infection in periods A and B. This suggests that a risk-based personal protective equipment (PPE) hospital policy for HCWs, where full PPE (N95 respirator, eye protection, gown, and gloves) was implemented in clinical areas managing COVID-19 suspected patients and universal surgical masks for other clinical areas (6), coupled with nation-wide mandatory face masks in all public areas even with the lifting of “Circuit Breaker” measures (7), was effective in protecting HCWs from COVID-19. Whilst the ARI incidence rate was similar in both periods, the higher proportion of HCWs who had served in non-COVID-19 areas observed among sick HCWs in period B suggests that HCWs were also at risk of acquiring ARI in non-COVID-19 areas as well as in the community. HCWs should be reminded to maintain the same level of vigilance for safe distancing and infection prevention and control, after work as when during work.
Although mass testing of HCWs has been suggested to prevent nosocomial transmission in the United Kingdom (8), our findings refute the necessity of mass screening in hospitals which have adequate PPE protocols for HCWs (9). Furthermore, with the low levels of community transmission of COVID-19 in Singapore (10), universal screening of pre-symptomatic and asymptomatic HCWs would provide very low yield as HCW positivity rates tended to reflect more on community than within hospital transmissions (9). Healthcare resources should be conserved for managing other critical medical needs which might have been neglected due to the competing demands of the COVID-19 pandemic.
Nevertheless, HCW surveillance programmes should be regularly updated as the COVID-19 pandemic evolves, and complemented with public health policies and infection prevention strategies, including safe distancing measures, judicious use of PPE, rigorous contact tracing and contact management (6).
The ongoing COVID-19 pandemic is likely to be long-drawn. HCWs are a precious resource in the battle against COVID-19. The protection of HCWs from COVID-19 is critical and becomes increasingly challenging as community transmissions are expected to increase with the resumption of economic and social activities and the lifting of travel bans. A robust HCW protection and enhanced sickness surveillance system is key in the early identification of COVID-19 in HCWs, to prevent nosocomial transmission in healthcare settings.
References
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