Effectiveness of an infection prevention strategy to limit exposure of high-risk patients to COVID-19 in a hospital-based subacute unit: a descriptive report

Abstract

The coronavirus (COVID-19) epidemic has put unprecedented stress on hospitals as well as skilled nursing facilities, where reside some of the most vulnerable individuals at high risk of mortality and complications of this infection. This report highlights the strategy and success of hospital infection prevention efforts to protect the residents of an in-hospital subacute unit with 24 at-risk patients with chronic pulmonary disease in northern California. Specific efforts are detailed, with results of surveillance testing reported, including both viral PCR and serological IgG assays. Implications for other long-term subacute care facilities are discussed, as well as advantages and specific challenges for ‘distinct part’ versus ‘free-standing’ subacute care units.

Introduction

Coronavirus disease (COVID-19) has been associated with critical outbreaks in long-term care facilities with multiple facilities and rapid spread of infection. In late February 2020, a long-term care facility in King County, Washington reported an infection involving 129 individuals, including 81 patients and 34 staff, of whom 23 persons died (McMichael et al., 2020). According to data reported by the California Department of Public Health, as of 9 May 2020, 1033 nursing home residents had died of COVID-19, accounting for 40% of the state’s 2585 deaths (California Department of Public Health, 2020). This is despite the fact that nursing home residents represent less than 1% of the state population (Johnson, 2020).

COVID-19 can spread rapidly within long-term residential facilities, where many residents have chronic medical conditions known to be at higher risk for poor outcomes. This report describes strategies and effectiveness of infection prevention efforts in a hospital-based long-term subacute facility in northern California for preventing exposure of high-risk patients. While most long-term adult subacute facilities in California are ‘free-standing’, many are also a ‘distinct part’ of an acute care hospital (Department of Health Care Services, 2020). This location within a larger acute facility may affect infection prevention strategies and have associated advantages in resources, while also presenting challenges in limiting exposure to acutely ill patients.

The unit described is a 24-bed subacute unit serving the long-term needs for adult patients, within a larger community hospital of 358 licensed beds in Santa Clara County, California. The unit is housed in a wing reserved solely for subacute patients with locked doors and access only to dedicated subacute staff. The mean age of subacute residents is 64.7 years (age range = 25–93 years), with a gender breakdown of 58% male and 42% female. Ethnicity breakdown is 54% Asian, 29% Hispanic/Latino, 13% Caucasian and 4% African American. All the residents have chronic care needs, with common medical morbidities including chronic respiratory failure (96%), chronic neurological disease – stroke, brain injury, encephalopathy (88%), diabetes mellitus (63%), chronic heart disease (25%), and chronic renal failure (13%). Body mass index (BMI) is a mean of 26.4 kg/m² (range = 19.6–36.6 kg/m²). Residents have been living in the unit for a mean length of 42.5 months (range = 1–103 months).

Methods

In late February 2020, it had become apparent that the prevalence of COVID-19 was spreading, with multiple documented travel-related cases in Santa Clara County and community spread in northern California. Hospital administration and the subacute medical director closed the unit on 2 March 2020. Since that date, there have been no visitors, no family and no vendors allowed. Please see Table 1 for details on unit infection prevention strategy and timeline. This effort corresponded with wider hospital initiatives, including a strict visitor restriction policy for acute patients, along with mandatory employee and physician screening upon entrance to the hospital, removal of any unnecessary support staff and work-at-home directives for non-clinical staff. The Public Health Officer of Santa Clara County enacted a mandatory ‘Shelter in Place’ directive on 16 March 2020, which remains in effect through the end of May (County of Santa Clara Public Health Department, 2020c).

Table 1.

IP timeline for the subacute unit.

10 February 2020	Initiation of ‘deep cleaning regiment’ using SAGE packet (skin antisepsis, oral and nasal cleaning) for every admission or return from outside unit
	Charge nurse cleans all hard surfaces in unit q-shift with bleach disinfectant
17 February 2020	Reinforced alcohol-based hand sanitiser and hand washing after every patient contact
	Implemented screening visitors for influenza-like symptoms and travel risk factors
24 February 2020	All meetings moved to virtual and phone platforms
	Designation of ‘Infection Control Champion’ for each nursing shift to monitor IP compliance
	Staggering of staff meal and other breaks to promote social distancing
	Requiring uniform changes at shift start, providing showers and changing rooms
2 March 2020	Unit closed to all visitors, vendors, contractors
	Virtual visiting implemented with deployment of iPad devices
	All group meals and activities cancelled
	Mandatory education of all staff on COVID-19 and hospital IP strategy
	Monitoring of all patients’ temperature q-shift
4 March 2020	Mandatory temperature screens for all hospital employees, physicians and vendors
9 March 2020	Hospital daily monitoring of PPE supply and burn rate/unit
	Addition of alcohol-based hand sanitiser at every door in unit
	Surveillance plan for all unit patients – screen for COVID-19 symptoms and signs
16 March 2020	Contingency unit staffing plan, added staff to facilitate surveillance
23 March 2020	Increased staff screening – temperature and COVID-19 signs/symptoms by written questionnaire
30 March 2020	Increased patient monitoring – q 4-h check for COVID-19 signs/symptoms
31 March 2020	Universal masking of all staff and physicians in the hospital
2 April 2020	Hand hygiene re-education and return observation for all unit staff
10 April 2020	Coordination with California Department of Public Health for increased unit surveillance and reporting per standardised survey
28 April 2020	Employee Health surveillance testing initiated for all hospital staff and physicians, PCR and serology
6 May 2020	Testing all unit residents with PCR and serology

IP, infection prevention; PPE, personal protective equipment.

During March and April 2020, three subacute patients from the unit required evaluation for fevers and influenza-like symptoms, requiring transfer to the main hospital and diagnostic work-up including COVID-19 testing. All three COVID-19 tests were eventually negative, though in one case, the time for the result was long enough that it required temporary removal from the subacute unit and cohort with other persons under investigation (PUIs).

On 6 May 2020, surveillance testing was performed for all 24 residents of the unit, after patients and families were informed. Testing was consistent with directives by the Santa Clara County Department of Public Health for screening at-risk patients (County of Santa Clara Public Health Department, 2020b). Nasopharyngeal swabs with PCR testing for COVID-19 viral DNA were performed, along with serological evaluation for antibody response to COVID-19. PCR testing was performed with CDC 2019-nCoV Real-Time RT-PCR Diagnostic Panel, which targets two distinct regions of the viral Nucleocapsid (N) gene target, both of which are unique to the SARS-CoV-2 virus.

Results

Results showed that none of the 24 residents returning positive results. Serological testing was performed using Diazyme’s DZ-Lite SARS-CoV-2 IgM/IgG CLIA Kit (Poway, CA, USA; manufacturer reported sensitivity 91.2%, specificity 97.3%) (Diazyme, 2020), which also underwent internal validation studies at the local hospital laboratory. Current assay protocol measures IgG, with reflex to IgM if positive. None of the 24 residents had evidence of serum IgG antibodies.

Discussion

The results of PCR testing and serological evaluation suggest that there was no evidence of exposure to the residents of this subacute unit to COVID-19, with an immunoassay sensitivity of 91.2%. Antibody testing for COVID-19 underwent internal validation studies at our health and hospital system laboratory before this project, with adequate ‘within-run’ and ‘between-run’ assay precision.

In February 2020, Silicon Valley was being described as the ‘epicenter’ of COVID-19 activity in California (Dolan and Rust, 2020). March and April 2020 were a period of intense COVID-19 activity in Santa Clara County, and for the hospital, with busy clinical services within the acute hospital, peaking with over 80 new diagnosed cases/day in early April (County of Santa Clara Public Health Department, 2020a). Likely underreported due to significant concurrent limitations in testing capacity, many of these patients nevertheless required hospitalisation. Hospitals opened dedicated cohorted COVID-19 units to meet these needs, hired additional staff, acquired additional ventilators and expanded intensive care unit space. As of 10 May 2020, these efforts have been viewed as a success, with Santa Clara County reporting 2307 total cases, but only 128 deaths (County of Santa Clara Public Health Department, 2020a).

Given the vulnerability of subacute patient populations, early interventions to safeguard the unit were initiated as detailed above. These initiatives were concurrent with hospital administrative directives to drastically limit all visitors, standardise the use of personal protective equipment (PPE), and cohort acute patients who were diagnosed with COVID-19 or being considered PUIs. The hospital also implemented programs for shower access for all staff, changing facilities and hospital-issue scrubs to avoid contamination of outside clothing. Additionally, the hospital implemented a COVID-19 ‘Tiger Team’ – a specialised, cross-functional team of educated nurses to address acute organisational needs within the hospital, 24 h/day.

Subacute families were generally supportive of these measures, as consistent with the public health directives and prioritising patient safety. Technology with iPad access was embraced by most and helped families to remain connected during this time.

Social distancing and shelter-at-home initiatives have been widely credited for reducing the spread of COVID-19 infection, though evidence is lacking. It makes intuitive sense based on theories of viral spread by droplet and contact that restriction of contact would limit exposure, and thus transmissibility. The World Health Organization (WHO) argues for ‘speed, scale and equity’ in public health response to COVID-19, to mitigate outbreak risk in high vulnerability settings. Specifically, the WHO ‘advocates appropriate measures in place to minimise risk of new outbreaks and nosocomial transmission’ (WHO, 2020a). On 21 March 2020, the WHO published interim guidance directing long-term care facilities to implement many of the specific standards which had been implemented in the weeks preceding at the subacute unit described (WHO, 2020b).

Limitations

This is not prospective research, but an observational report with surveillance testing of a high-risk patient population. There is no control group, and it is conceivable that, without any intervention or change in practice, COVID-19 would not have reached this subacute unit. However, given the apparent effectiveness of social distancing and shelter-in-place directives and current understanding of viral disease transmission, a controlled study would not be ethical.

Neither the PCR testing nor the serological immunoassays have perfect sensitivity, and it is also possible that there could be false negatives in surveillance testing. However, in this asymptomatic patient population, this is not highly likely. Concurrent asymptomatic staff testing among hospital employees have yielded COVID-19 PCR positive rates of 0.3%. Finally, it is possible that immunological response and production of IgG could be limited in a chronically ill patient population. It should be noted that there were no deaths or unexplained severe illness during this time period that could be potentially attributed to undiagnosed COVID-19 infection.

Conclusion

This brief report describes a single subacute unit, a ‘distinct part’ of a larger acute community hospital, where early infection prevention strategies were proactively implemented and ultimately may have contributed to limiting exposure and risk. Although sharing physical space with a larger healthcare organisation caring for sick patients with COVID-19 may seem to imply increased risk versus ‘free-standing’ subacute units, there may be advantages that lead to nimble organisational responses with regard to infection prevention. Depth of resources, access to testing and broader perspective from acute care experience may aid subacute facilities that represent a ‘distinct part’ of larger organisations. Additionally, when subacute patients become acutely ill from COVID-19 or other causes, they may be tested, treated and cohorted efficiently within the same medical centre, obviating the cost and discomfort of an ambulance ride and avoiding delays associated with transfer.

Finally, these data represent the first published serological dataset with antibody testing of a high-risk patient group in a congregate setting, including sampling of every unit patient and correlation with PCR viral testing. It is hoped that this experience will benefit others in the subacute treatment space and lead to more definitive study of infection prevention strategy for COVID-19.