COVID-19 re-infection in Shahroud, Iran: a follow-up study.

Although many people became infected and recovered during the COVID-19 epidemic, the immunity duration and re-infection in recovered patients have recently attracted many researchers. The aim of this study was to evaluate the recurrence of the infection in recovered individuals over a 9-month period after the onset of the COVID-19 epidemic. In this study, data related to COVID-19 patients in Shahroud city were collected using the electronic system for registering suspicious patients and also by checking patients' hospital records. In this study, from 20 March 2020 to 20 November 2020 (9 months), a total of 8734 suspected patients with respiratory symptoms were observed and followed up. RT-PCR was positive for 4039 patients. During this period, out of the total number of positive cases of COVID-19, 10 cases became re-infected after complete recovery. The risk of re-infection was 2.5 per thousand (0.95 CI 1.2-4.5). The mean time interval between the first infection and re-infection was 134.4 ± 64.5 days (range 41-234 days). The risk of re-infection between male and females was not statistically different (1.98 per 1000 women and 2.96 per 1000 men). Exposure to COVID-19 may not establish long-term protective immunity to all patients and may predispose them to re-infection. This fact can be reminded that the use of masks, social distancing and other preventive measures are very important in recovered patients and should be emphasised especially in health care personnel who are more exposed to the virus.

Risk Factors Associated with Mortality in COVID-19 Patient's: Survival Analysis.

Background: The effect of related factors on recovery or death rates may vary from country to country. Therefore, we aimed to investigate the relationship between demographic, clinical, laboratory factors on the survival rates of confirmed cases of COVID-19 in Shahroud, Iran. Methods: This is an analytical study of the estimation of the survival of patients with COVID-19. Patients who had positive PCR test were considered as COVID-19 cases, and the 2-month survival of these patients was estimated. Among the diseases, heart disease and diabetes were considered as separate variables, and the patients' histories of other diseases were included in the model as comorbidities. Results: Of 396 confirmed patients hospitalized, 109 patients (27.5%) had a history of heart disease, 100 (25.3%) were diabetic, and 80 (20.2%) had a history of other comorbidities. The number of deaths due to the disease was 59 (14.9%). The median age of those who died was 76 years. The multivariate Cox regression analysis shows that heart disease increases hazard ratio more than two times (HR=2.37, 95% CI: 1.33-4.23). The neutrophil-to-lymphocyte ratio (NLR) factor, (HR=1.15, 95% 1.08-1.22), and older age (HR=1.06, 95% CI: 1.03-1.08) increases the risk of death significantly. Conclusion: The heart disease history, NLR factor and older age are associated with death of COVID-19 and may be helpful for the early warning and prediction of disease progression.