Characterisation of the underlying mechanisms of long-term COVID-19 sequelae is still ground for ongoing research; sequelae may result from irreversible organ damage during the acute infection phase, or may reflect the manifestations secondary to a persistent hyperinflammatory state or ongoing viral activity with poor host antibody response. This chapter presents a summary of the evidence available as at October 2021 regarding the different manifestations and severity of post-COVID-19 sequelae in adult patients.
Recurrence, relapse and readmission after recoveryRecurrence and relapse of COVID-19Re-infection with SARS-CoV-2 has emerged as a possible outcome after full recovery from COVID-19. Several authors have reported that patients might present with a new positive respiratory sample after previous negative results. TO et al. [7] reported a real case of COVID-19 recurrence; they documented re-infection by a different strain of SARS-CoV-2 with IgG seroconversion. Conversely, KANG et al. [8] analysed 292 re-positive cases from South Korea; patients were asymptomatic or reported minor symptoms and the authors concluded that new positive samples were probably due to previous false-negative laboratory tests or persistent viral shedding rather than real re-infection.A systematic review of published evidence identified 1350 similar cases [9]. The re-positivity occurred mainly in asymptomatic patients; interestingly, only 5.6% of patients were pyrexial mean±SD 34.5±18.7 days after the initial onset of symptoms. Fortunately, the outcome was favourable in the majority of cases (96.7%) and only 2.1% died. GIDARI et al.[9] evaluated a total of nine re-positive patients and inoculated six new positive respiratory samples in Vero-E6 cells showing no growth and negative PCR results. This suggests an absence of live virus in re-positive patients who, therefore, should be considered not contagious. The authors hypothesised that this phenomenon was due to prolonged RNA persistence in the upper respiratory tract [9]. A meta-analysis of potential COVID-19 recurrence included >30,000 publications and analysed patient data for age, sex, time of re-occurrence or relapse of symptoms, and a persistent SARS-CoV-2 PCR test [10]. Relapse occurred after a mean±SD of 34±10.5 days of recovery. This group reported persistent positive SARS-CoV-2 results 39±9 days after the initial positive testing. Relapse predominantly occurred in older individuals with an anergic immune response. There were no reports of any clinical re-infections after a 70-day period following initial infection.
Readmission and death in post-COVID-19Readmission and death after hospital discharge contribute to the burden of the disease. An observational study based in a large multihospital system in Michigan (USA) included 2179 hospitalised patients and reported readmission and death within 60 days of discharge in 19.9% and 9.1% of patients, respectively [11]. The most common reasons for readmission were COVID-19 (30.2%), sepsis (8.5%), pneumonia (3.1%) and heart failure ...