Long COVID-19
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study, even of the 439 patients who had not required oxygen in the hospital, 81% reported at least one symptom after 6 months, including 66% fatigue and muscle weakness (Huang 2021). In another large study of 669 patients from Switzerland treated exclusively as outpatients, as many as 32% still had at least one symptom after 6 weeks (Nehme 2020). Long periods of disability are seen even in mild courses (see cases in the box). Of hospitalized patients, almost one-third are unable to work after 3 months (Garrigues 2020, Chopra 2020). The often highly fluctuating course is striking: in a cross-sectional analysis of 70 “long haulers”, the course of symptoms was intermittent in 43% of the cases, alternating symptom-free intervals of a few days or hours with sudden relapses, often worsening after physical or intellectual exercise (SalmonCeron 2020).
Studies with objectifiable tests A selection of studies that focused on objectifiable tests and parameters is presented below. Again, it is important to consider different follow-up duration, but also the selection of the case population studied. In most studies, there was not only a correlation between the findings and the severity of acute COVID-19 but also a marked improvement over time. However, whether the remaining radiological or pulmonary diffusion abnormalities completely resolve needs to be investigated in future follow-up studies.
Pulmonary function •
Of 145 patients in a prospective study from Germany and Austria (75% hospitalized, 22% in ICU), 41% exhibited persistent symptoms (36% dyspnea) 100 days after COVID-19 onset. CT scans unveiled persistent lung pathologies in 63%, mainly consisting of bilateral ground-glass opacities, without radiological signs of pulmonary fibrosis. However, sequential follow-up evaluations at 60 and 100 days after COVID-19 onset demonstrated a vast improvement of both, symptoms and CT abnormalities over time. One-third displayed an impaired lung function, with a reduced diffusing capacity being the most prominent finding even more than 100 days after COVID-19 diagnosis (Sonnweber 2020).
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In the Wuhan cohort, a subgroup was tested for diffusion capacity for carbon monoxide (DLCO) at 6 months of follow-up. A low DLCO (< 80% of predicted) was found in 50% (48/86) and in 29% (66/228) in those
COVID Reference ENG 006.9
