When should residents and staff in long-term care settings be tested for Covid-19 (Coronavirus disease 2019) and influenza (flu)?

When to Test for COVID-19 and Influenza in Long-Term Care Settings

Test all residents and staff weekly for COVID-19 when there are no active outbreaks, and immediately test any resident or staff member with respiratory symptoms, behavioral changes, or atypical presentations including fever, hypothermia, diarrhea, falls, or delirium during influenza season or COVID-19 community transmission. 1, 2

COVID-19 Testing Strategy

Routine Surveillance Testing

• Conduct weekly testing of all residents and staff in facilities without active outbreaks using rapid antigen tests or PCR testing 1
• This proactive approach is critical because symptom-based screening alone fails to identify approximately 50% of COVID-19 cases in long-term care facilities 3
• Asymptomatic and presymptomatic residents can have high viral loads (low RT-PCR cycle threshold values) indicating substantial transmission potential 3

Outbreak Response Testing

• Increase testing frequency to every 3 days once a single COVID-19 case is identified in the facility 1
• Test all residents immediately when one confirmed case is detected, as rapid dissemination is common with attack rates approaching 48% within 7 days 4
• Use nasopharyngeal swabs for SARS-CoV-2 testing via RT-PCR or rapid antigen tests, with rapid tests preferred when available for faster cohorting decisions 1

Symptom-Based Testing Triggers for COVID-19

Test residents presenting with:

• Atypical presentations that may precede respiratory symptoms: diarrhea (26% of cases), falls (18%), fluctuating temperature with hypothermia (34%), or delirium 4
• Classic respiratory symptoms: cough, shortness of breath, or oxygen desaturation 4
• Fever or subfebrility and fatigue, particularly in male residents 5
• Any behavioral changes without obvious cause 2

Critical pitfall: Waiting for classic respiratory symptoms delays diagnosis by days, allowing widespread transmission. The atypical presentation in older adults—with diarrhea, falls, or delirium appearing first—explains rapid outbreak propagation 4.

Influenza Testing Strategy

Outbreak Detection and Response

• Implement active surveillance immediately when one laboratory-confirmed influenza case is identified in the facility 2
• Initiate outbreak control measures (including testing, antiviral chemoprophylaxis, and isolation) when 2 cases of healthcare-associated laboratory-confirmed influenza are identified within 72 hours of each other on the same ward or unit 2
• Consider implementing outbreak measures if one or more residents has suspected influenza and molecular testing results are not available same-day 2

Who to Test During Influenza Season

During an identified outbreak, test any resident with: 2

• One or more acute respiratory symptoms (with or without fever)
• Temperature elevation or reduction without respiratory symptoms
• Behavioral change without respiratory symptoms

Specimen Collection for Influenza

• Obtain separate nasopharyngeal and throat swabs within 24-48 hours of symptom onset for optimal viral isolation 2
• Combine swabs in refrigerated viral transport media and transport on ice within 1-2 hours to experienced laboratory 2
• Rapid antigen tests have 40-80% sensitivity but enable faster isolation and prophylaxis decisions, significantly reducing outbreak duration and hospitalization costs 2
• RT-PCR testing is more sensitive and specific but more expensive 2

Important consideration: Additional diagnostic efforts beyond clinical-epidemiologic diagnosis are warranted in long-term care facilities because non-influenza A respiratory viruses (influenza B, parainfluenza, respiratory syncytial virus, metapneumovirus) frequently cause severe illness requiring different management 2.

Dual Testing Approach During Respiratory Illness Season

When community transmission of both pathogens is occurring:

• Test for both COVID-19 and influenza simultaneously in any resident with respiratory symptoms or atypical presentations 1, 2
• Maintain weekly COVID-19 surveillance even during influenza season 1
• The overlapping atypical presentations (fever, hypothermia, behavioral changes, falls) in older adults make clinical differentiation unreliable 4, 2

Staff Testing Requirements

• Test all staff weekly during routine surveillance periods 1
• Test symptomatic staff immediately before allowing facility entry 2
• During outbreaks, 27.5% of staff may be COVID-19 positive, often while working asymptomatically 4
• Staff should report symptoms immediately and undergo testing before returning to work 2

Laboratory Evaluation Beyond Viral Testing

For residents with suspected infection (COVID-19 or influenza):

• Obtain CBC with manual differential within 12-24 hours of symptom onset 2
• Left shift (band neutrophils ≥6% or ≥1,500 cells/mm³) or leukocytosis (WBC ≥14,000 cells/mm³) warrants careful assessment for bacterial superinfection, even without fever 2, 6
• This is particularly important as bacterial pneumonia complicates influenza in 7% of long-term care facility outbreaks 2

The evidence strongly supports proactive, frequent testing rather than symptom-based approaches alone, as the latter consistently misses approximately half of cases in this vulnerable population, allowing preventable transmission and mortality.