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Aims:  This study aimed to investigate persistent symptoms of coronavirus disease 2019 (COVID-19) patients admitted to a general tertiary teaching hospital during a 9-month follow-up period.
Materials & Methods: In this study, 400 hospitalized COVID-19 patients in Iran were studied, among them 78 RT-qPCR positive cases were identified from February 19 to March 18, 2020. After excluding readmitted and deceased patients, 75 cases underwent in-hospital follow-up. Out-of-hospital follow-up was done for 57 living patients, of whom four cases were unreachable, and five cases died after discharge. The remaining 48 participants were followed up for nine months, and their symptoms and complaints were checked by regular visits to the infectious disease clinic and telephone calls via a checklist designed by the authors.
Findings: The mean age of RT-qPCR positive hospitalized patients was 54.64 ± 17.42 years, and 38.7% of them were female. Overall, five (10.4%) patients complained of dyspnea, three (6.2%) patients of olfactory nerve complications, three (6.2%) patients of persistent fatigue, and two (4.2%) patients of prolonged cough up to the end of the follow-up period. New-onset symptoms were reported in five (10.4%) patients; in most of them (4 out of 5), these symptoms were neurological (urinary retention, tremor with ataxia, distraction, and insomnia).
Conclusion: A large proportion of patients who recover from COVID-19 infection experience prolonged symptoms. Further investigations should be done to provid more data on the underlying causes and risk factors of developing these post-COVID conditions.

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The Assessment of strain accumulation due to nonlinear events like creep, plasticity or ratcheting phenomenon has gained importance, since it causes an increase in creep and fatigue damage of materials. Some factors like the magnitude of loading, constitutive equations or the elastic regions around the nonlinear events have effect on the rate of strain accumulation. The elastic follow-up can explain the mechanism of strain accumulation. This phenomenon may occur when a mechanical structure with elastic manner is connected to non-linear events and they are subjected to a displacement load. In these cases, the high rigidity portion of elastic region of mechanical structure may enhance the force to the regions with low rigidity. So in the local non-linear portion, the strain is accumulated. This phenomenon is proposed as an important instruction in mechanical assessment codes. In this study, the effects of Elastic Follow-up phenomenon on strain accumulation due to elastic-plastic and local creep are investigated. So the Elastic Follow-up parameter is defined by the methods which are described in high temperature assessment procedures (R5). The results revealed that the strain accumulation depends on the elastic region in structures which is described by the Elastic Follow-up phenomenon.