The SARS-CoV-2 Omicron BA.5 strain was the dominant variant in Portugal between May and September 2022. As far as we know, there is no data on the infectious period of the BA.5 strain.
Rapid antigen detection tests (RADTs) have high sensitivity for early detection of patients with high viral load and are equally useful to certify the end of the transmission period. Early studies suggest a viral shedding period of 5.35 days for Omicron BA.1 and BA.2, but these studies do not address BA.5.
The authors intended to assess whether patients remain positive beyond 5 days after the onset of symptoms (D5) or according to the days recommended by the Direção Geral da Saúde (DGS), and the number of days to end isolation. An analysis of consecutive patients admitted to a hospital with a confirmed diagnosis of COVID by RT PCR was performed. Adult patients who underwent serial RADTs after D5 (or later), with 2 or 3 days of interval, until obtaining a negative test were included.
Seventy-two patients were included, with a mean age of 77 years-old. None of the patients had COVID-19 before. The mean number of positive test days was 14.24 ± 5.32. Regarding comorbidities, 56.9% of patients have hypertension, 26.4% ischemic stroke and 25% heart failure.
We conclude that almost all patients (98.6%) remain positive on D5 and beyond. Vaccination reduces disease severity and ischemic stroke increases the risk of severe disease, which was not considered in DGS comorbidities. The RADTs allow to reduce the isolation time in patients with severe disease.