COVID-19: Despite Strict Hygiene, Asymptomatic Transmission Rate High at Skilled Nursing Facility

Screening via real-time polymerase chain reaction (PCR) and serology at a single nursing facility that had no known cases of SARS-CoV-2 (coronavirus disease 2019; COVID-19) revealed an 85% prevalence of the virus among residents and a 37% prevalence among staff, according to data published in Clinical Infectious Diseases.

Serologic testing was not helpful in the identification of infections, the researchers also found.

Despite measures put in place to protect older and chronically ill people who are at higher risk for morbidity and mortality from COVID-19, high infection rates have been reported in skilled nursing and long-term care facilities. Emerging reports of asymptomatic spread in these facilities led to the universal screening of patients and staff at a 142-bed, skilled nursing facility before its designation as a dedicated COVID-19 rehabilitation center.

The facility in Massachusetts is separated into short-term care, long-term care, and a memory unit. At the time of selection as a dedicated rehab facility there were no confirmed or suspected cases of COVID-19 among staff or residents. Prior to resident relocation and in preparation for reassignment of the facility, nasopharyngeal swabs were taken from all 97 patients. Five days later, swabs were collected from 45 residents who initially tested negative for SARS-CoV-2; 31 of these patients also had blood drawn for serologic testing. The next day, nasopharyngeal samples were collected from 97 staff members, and blood samples were taken from 84 staff members and an additional 25 residents. At the time of testing, the average age of residents was 83 years (range, 54-102 years; interquartile range [IQR], 61-98). All residents were asymptomatic at the time of initial testing according to daily symptom screening. Chronic respiratory illnesses were present in 20.6% of residents with available health records.

Results of the initial 97 tests were 53.6% positive with significantly more patients in the memory unit testing positive (75%), compared with both the short-term and long-term units (53.3% and 34.3%, respectively; P <.01). Repeated testing of the initial 45 negative patients found 69% now tested positive. Together, the 2 rounds of testing found that 85% of the 97 residents tested positive for SARS-CoV-2. The mean cycle threshold value for residents screened in the second round of testing (20.8; 95% CI, 19.0-22.6) was significantly lower than for those tested in the first round of testing (23.3; 95% CI, 21.3-25.3; P <.05). Serological tests performed in 56 residents found that 80% of residents were negative for both immunoglobulin M (IgM) and immunoglobulin G (IgG). In the 2 weeks after initial testing, 30 residents died, 24 of whom tested positive.

The 97 staff members who were tested represented 66% of the total staff and were aged 45 years on average. Of these staff members, 37.1% tested positive; the mean cycle threshold was not significantly different than the resident cohort (22.4; 95% CI, 20.9-23.9). Antibody tests were negative for both IgG and IgM in 80 of the 84 staff members tested.

These results were found despite the facility having in place strict visitation and patient and staff screening policies. This included daily symptom and temperature checks. Infection control policies were also in place for 2 weeks prior to testing; this included universal masking for all staff and increased attention to hand hygiene. Residents were also required to wear masks whenever leaving their rooms. Facility admissions were heavily restricted, and only 3 patients transferred into the facility within the 2-week period prior to testing.

According to investigators there are multiple explanations for the high prevalence. “Despite social distancing policies, residents continued to intermingle due to difficulty restricting patient movements,” they wrote. “This was a particular challenge in the memory unit, likely contributing to a significantly higher prevalence of disease.” It is also possible that cases were missed and symptoms instead attributed to chronic respiratory illness.

Results from this study may not be generalizable outside of this single center, and clinical data including causes of death were limited. Furthermore, it is challenging to verify that this population was asymptomatic before the study. This may be in part due to the cognitive impairment of residents and baseline respiratory conditions leading to unrecognized symptoms. Finally, only 66% of staff opted for voluntary testing, which may have produced an over- or underestimate of disease prevalence.

Investigators conclude that in these facilities, “Simply screening for symptoms is no longer enough.” While they agreed that intensive infection prevention interventions are essential, they may be insufficient.

“Widespread testing among nursing home residents must be implemented, and staff must be included in testing to identify cases early and avoid staff transmission,” they concluded. “Until preventative and curative therapies become available, increased testing, meticulous infection control, and advance care planning are essential in caring for this vulnerable population.”

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Goldberg SA, Lennerz J, Klompas M, et al. Presymptomatic transmission of SARS-CoV-2 amongst residents and staff at a skilled nursing facility: Results of real-time PCR and serologic testing. [published online July 15, 2020]. Clin Infect Dis. doi:10.1093/cid/ciaa991