*Purpose: COVID-19 is a novel viral illness associated with significantly worse mortality, prolonged disease course, and extended periods of viral shedding in transplant patients on long-term immunosuppression. While prior case series have demonstrated extended disease duration in immunosuppressed kidney transplant patients, few have quantified the differences in viral shedding between immunosuppressed and immunocompetent patients. We provide the first case series demonstrating that immunosuppressed transplant patients have significantly higher viral loads, as measured through non-invasive environmental sampling.

*Methods: We quantified viral particles on representative surfaces from the rooms of two patients on tacrolimus therapy with a history of renal transplant and compared against non-immunosuppressed patient. All patients had a SARS-CoV-2 positive nasopharyngeal swab within 48 hours of sampling and were symptomatic. Matched non-transplant patients were 3-4 days from initial symptoms while transplant patients were 3-4 weeks. Samples were collected using polyester-tipped swabs pre-soaked in DNA/RNA Shield (Zymo Research) for 1 minute. One-step quantitative real time-polymerase chain reaction performed using TaqPath 1-Step qRT-PCR Master Mix on the LightCycler® 480 System. Samples were run in triplicate for N1 and N2 primers and probes (IDT) recommended by the CDC. The viral copy count from each raw sample was divided by its respective surface area to calculate viral copies/cm².

*Results: Despite the increased time between initial positive test result and sample collection, kidney-transplant patients on tacrolimus therapy demonstrated higher viral loads on associated bedrails, flooring, and bathroom flushes compared to the matched, non-immunosuppressed patients.

*Conclusions: This data raises a warning that immunocompromised individuals may shed higher levels of virus into their environment, likely through both aerosol and fecal mechanisms. Previous research has shown non-immunosuppressed individuals carry diminished environmental shedding by 21 days and may be safe to return to public service and general hospital floors, yet no similar analysis has been performed on immunosuppressed transplant patients. Our findings suggest that hospitals must take extensive isolation precautions when treating immunocompromised patients who have tested positive for SARS-CoV-2 due to the potential increase in the quantity of infectious virus particles.

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