[Three cases of COVID-19 in elderly patients with delayed release from isolation due to persistent positive polymerase chain reaction findings].

The coronavirus disease 2019 (COVID-19) infection has spread worldwide, with no sign of its control in Japan yet. Eight elderly COVID-19 patients over 90 years of age were treated at our hospital. We herein report three cases with characteristic progression. Case 1 was a 91-year-old female patient diagnosed with bacterial pneumonia previously who did not show improvement with medication; thus, she was transferred to our hospital 16 days after the onset. She was diagnosed with COVID-19 using the SARS-CoV-2 polymerase chain reaction (PCR) test. Favipiravir, methylprednisolone, and unfractionated heparin were administered, but she only tested negative 68 days after the onset, at which point she was discharged. However, she was transferred back to our hospital 80 days after the onset since she tested positive again. She was transferred to another hospital 110 days after the onset without testing negative. Case 2 was a 102-year-old female. Despite being a mild case, it took 32 days to obtain negative PCR findings, leading to a decline in the activities of daily living. Case 3 was a 90-year-old male patient treated with favipiravir, dexamethasone, and unfractionated heparin, but his condition deteriorated. He never tested negative for PCR and ultimately died 20 days after the onset. Reports suggest that PCR positivity does not necessarily indicate infectivity, but there are no clear criteria for lifting a quarantine. Therefore, PCR negativity is often sought for "peace of mind." In the current situation where hospitals are fully occupied, clear criteria for lifting the quarantine should be promptly determined. After the completion of treatment, it is more important to monitor symptoms and take standard precautions, such as daily health monitoring, wearing a mask, and keeping an appropriate distance from others, than to obtain a negative PCR result.