Testing Whole Nursing Homes for COVID-19, 2020: Every Day of Delay Meant 1.3 More Cases

Unrecognized SARS-CoV-2 infections fuel spread in nursing homes, where large outbreaks have killed many residents. Testing every resident and staff member at once — facility-wide testing — can catch infections before symptoms appear and guide infection control. CDC pooled results from seven state or local health departments that did this in 288 nursing homes between March 24 and June 14, 2020.

Two strategies

Testing was by RT-PCR on nose swabs (one department also used a point-of-care test), with results back in 1 to 7 days.

Where there was already a case: find it fast

In the targeted homes:

• Of 13,443 people tested, 1,619 (12%) were positive.
• 79% of homes turned up new, unrecognized cases (median 6).
• In the 88 homes with a documented case before testing, the gap from first case to finished testing ranged 1–41 days (median 7). Each extra day was linked to 1.3 more cases found.

Positive results after facility-wide testing against days from first case to completed testing, five jurisdictions, March–June 2020. Image from CDC's report

• Where resident and staff results could be separated (62 homes), about 1.3 staff cases turned up for every three resident cases; in 45 homes with a positive resident, an average 5.2% of tested staff were positive (range 0%–26%).

Where there wasn't: few positives

In the statewide program, local 14-day incidence was low (medians of 19 and 38 per 100,000).

County incidence didn't predict which case-free homes would turn up a case.

A resident case matters most. Under both strategies, homes that already had a resident case found the most new cases on average (25.7 targeted, 7.3 statewide), against 3.5 and 0.3 where only staff had been infected and 0.8 and 0.4 where no case was known.

What it means

• Test everyone as soon as possible after a first case, with fast turnaround. It finds hidden cases and makes cohorting (dedicated space and staff for infected residents) and isolation more workable.
• Staff and resident infections go together, and staff infection rates were often higher than community surveys in low-incidence areas would suggest — pointing to spread in the workplace, between residents and staff and among staff. Test both, and keep infected staff home under nonpunitive sick-leave policies.
• In homes with no cases in low-incidence areas, many tests find few cases. Testing could focus on those at highest risk — staff from high-incidence areas, residents recently hospitalized or on dialysis — or use faster, cheaper approaches: point-of-care tests, pooled samples, self-collected saliva or nasal swabs, or wastewater surveillance.
• Health departments should make sure nursing homes have the resources to test everyone quickly after a case.

Limits: symptoms weren't recorded at testing; infection control and follow-up couldn't be described; testing can miss people still incubating or no longer shedding virus, especially with less sensitive rapid tests (results held when Detroit, which used one, was excluded); the per-day estimate covers delays of 1–41 days only; and the statewide programs ran where community incidence was low.

Sources

Based on Kelly M. Hatfield, Sujan C. Reddy, Kaitlin Forsberg, Lauren Korhonen and others, "Facility-Wide Testing for SARS-CoV-2 in Nursing Homes — Seven U.S. Jurisdictions, March–June 2020," MMWR, volume 69, Centers for Disease Control and Prevention; a work of the United States government in the public domain.