Are Presymptomatic SARS-CoV-2 Infections in Nursing Home Residents Unrecognised Symptomatic Infections?

Sequence and Metadata From Weekly Testing in an Extensive Nursing Home Outbreak

Judith H. van den Besselaar; Reina S. Sikkema; Fleur M.H P. A. Koene; Laura W. van Buul; Bas B. Oude Munnink; Ine Frénay; René teWitt; Marion P.G. Koopmans; Cees M.P.M. Hertogh; Bianca M. Buurman


Age Ageing. 2021;50(5):1454-1463. 

In This Article

Abstract and Introduction


Background: Sars-CoV-2 outbreaks resulted in a high case fatality rate in nursing homes (NH) worldwide. It is unknown to which extent presymptomatic residents and staff contribute to the spread of the virus.

Aims: To assess the contribution of asymptomatic and presymptomatic residents and staff in SARS-CoV-2 transmission during a large outbreak in a Dutch NH.

Methods: Observational study in a 185-bed NH with two consecutive testing strategies: testing of symptomatic cases only, followed by weekly facility-wide testing of staff and residents regardless of symptoms. Nasopharyngeal and oropharyngeal testing with RT-PCR for SARs-CoV-2, including sequencing of positive samples, was conducted with a standardised symptom assessment.

Results: 185 residents and 244 staff participated. Sequencing identified one cluster. In the symptom-based test strategy period, 3/39 residents were presymptomatic versus 38/74 residents in the period of weekly facility-wide testing (P-value < 0.001). In total, 51/59 (91.1%) of SARS-CoV-2 positive staff was symptomatic, with no difference between both testing strategies (P-value 0.763). Loss of smell and taste, sore throat, headache or myalga was hardly reported in residents compared to staff (P-value <0.001). Median Ct-value of presymptomatic residents was 21.3, which did not differ from symptomatic (20.8) or asymptomatic (20.5) residents (P-value 0.624).

Conclusions: Symptoms in residents and staff are insufficiently recognised, reported or attributed to a possible SARS-CoV-2 infection. However, residents without (recognised) symptoms showed the same potential for viral shedding as residents with symptoms. Weekly testing was an effective strategy for early identification of SARS-Cov-2 cases, resulting in fast mitigation of the outbreak.


Worldwide, nursing homes (NHs) are facing outbreaks of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) with high case fatality rates.[1,2] The current ECDC-guideline recommends expanded viral testing of asymptomatic residents in NHs if a single new case of a SARS-CoV-2 infection is detected, based on data of previous NH outbreaks which suggest an important role for presymptomatic spread of SARS-COV-2 among residents.[3–9] However, it remains unknown to which extent asymptomatic and presymptomatic cases contribute to the spread of SARS-CoV-2. Also, specifically in the NH setting, it remains unclear to what extent asymptomatic cases are truly without symptoms. Sole reliance on symptoms for testing in NHs could be insufficient because self-reporting of complaints is often compromised in residents due to limited ability to communicate (e.g. in residents with dementia).[10] The Dutch guideline for COVID-19 in NHs states that only residents with possible symptoms of SARS-CoV-2 should be tested[11] and no policy for testing of asymptomatic residents or staff is facilitated in the Netherlands.

Multiple reports have been published about the prevalence of asymptomatic and presymptomatic residents and staff in NHs after the implementation of a facility-wide testing strategy during an outbreak.[4,6,9,12,13] The prevalence of asymptomatic staff and residents differed from single cases to up to half of the infected cases. Low cycle threshold (Ct) values were found in asymptomatic and presymptomatic cases, suggesting potential of viral shedding.[6,9] A large registry of 857 Dutch residents with confirmed SARS-CoV-2 showed that 93% of cases expressed any of the symptoms cough, shortness of breath, or fever. A large range of other symptoms were also reported such as fatigue, diminished intake, gastro-intestinal symptoms, malaise or rhinorrhea.[14] However, the presentation of SARS-CoV-2 can be difficult to recognise in NH residents, which can cause delay in testing, isolation and treatment.[14,15] In addition, during a community-wide outbreak it can be difficult to distinguish residential outbreaks from multiple introductions without sequencing of viruses from cases.[16]

Viral spread by presymptomatic or unrecognised symptomatic cases has important implications for Personal Protective Equipment (PPE) use, facility-wide testing and isolation measures in NHs for the prevention of outbreaks. The aim of this study is to analyse the contribution of presymptomatic spread of SARS-CoV-2 in all staff and residents of a NH in the Netherlands by serial weekly point prevalence surveys, PCR and sequencing.