In critically ill patients affected by the coronavirus-19 disease (COVID19), reactivation of herpes simplex virus-1 (HSV-1) may be associated with increased length of intensive care unit (ICU) stay and higher mortality.

We conducted a retrospective cohort study from November 2021 to April 2022, of consecutive ICU patients diagnosed with post-COVID19 HSV-1 pneumonitis-related acute respiratory distress syndrome (ARDS). The study aimed to determine the timing of HSV-1 detection, clinical characteristics, and outcome.

A total of 91 patients were included in the study and 9 of them were diagnosed with post-COVID19 HSV-1 pneumonitis at a mean of 16.5 days after ICU admission. Bronchoalveolar lavage (BAL) was performed in 8 of the 9 patients, while bronchial washings were obtained in all 9 patients, with an average of approximately three bronchial washing samples per patient. Of these, 62.5 % (5/8) of BAL specimens and 334.7 % (8/23) of BW yielded HSV-1 by quantitative PCR. The primary symptoms in these patients were fever, hypoxemia, and purulent tracheal secretions. Additionally, patients in this cohort received multiple sessions of prone positioning, and 44.4 % were placed on extracorporeal membrane oxygenation (ECMO). Their average length of stay in ICU was 50 days. Three patients (33.3 %) died during their hospital stay.

In this small retrospective cohort HSV-1 reactivation study no significant association with mortality was observed; however, due to the limited sample size, our study was underpowered to detect small or moderate differences in outcomes. These findings should be interpreted as preliminary and hypothesis-generating.