Introduction Many individuals test positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA after recovering from the coronavirus disease (COVID-19), but the incidence of reactivation is unknown. We, therefore, estimated the incidence of reactivation among individuals who had recovered from COVID-19 and determined its predictors. Methods In this retrospective cohort study, patients with COVID-19 were followed up for at least 14 days after two consecutive negative SARS-CoV-2 polymerase chain reaction test results obtained ≥24 hours apart, and the frequency of SARS-CoV-2 reactivation was assessed. Results Of the 109 patients, 29 (27%) experienced reactivation, and seven (24%) of these were symptomatic. The mean period for the real-time PCR tests for SARS-CoV-2 from negative to positive results was 17 days. Compared with patients without reactivation, those with reactivation were significantly younger and more likely to have a lymphocyte count of <1500/µL (odds ratio [OR]: 0.34, 95% confidence interval [CI]: 0.12–0.94) and two or fewer symptoms (OR: 0.20, 95% CI: 0.07–0.55) during the initial episode. Conclusion Risk-stratified surveillance should be conducted among patients who have recovered from COVID-19.

BackgroundSevere fever with thrombocytopenia syndrome (SFTS) caused by the SFTS virus is an emerging infectious disease that was first identified in the rural areas of China in 2011. Severe cases often result in death due to multiple organ failure. To date, there are still numerous problems remain unresolved in SFTS, including unclear pathogenesis, lack of specific treatment, and no effective vaccines available.AimTo analyze the clinical information of patients with early-stage SFTS and to establish a nomogram for the mortality risk.MethodsBetween April 2011 and December 2018, data on consecutive patients who were diagnosed with SFTS were prospectively collected from five medical centers distributed in central and northeastern China. Multivariable Cox analyses were used to identify the factors independently associated with mortality. A nomogram for mortality was established using those factors.ResultsDuring the study period, 429 consecutive patients were diagnosed with SFTS at the early stage of the disease (within 7 days of fever), among whom 69 (16.1%) died within 28 days. The multivariable Cox proportional hazard regression analysis showed that low lymphocyte percentage, early-stage encephalopathy, and elevated concentration of serum LDH and BUN were independent risk factors for fatal outcomes. Received-operating characteristic curves for 7-, 14-, and 28-days survival had AUCs of 0.944 (95% CI: 0.920–0.968), 0.924 (95% CI: 0.896–0.953), and 0.924 (95% CI: 0.895–0.952), respectively. Among low-risk patients, 6 patients died (2.2%). Among moderate-risk patients, 25 patients died (24.0%, hazard ratio (HR) = 11.957). Among high-risk patients, the mortality rate was 69.1% (HR = 57.768).ConclusionWe established a simple and practical clinical scoring system, through which we can identify critically ill patients and provide intensive medical intervention for patients as soon as possible to reduce mortality.

Background The extensive geographical distribution and high mortality rate of severe fever with thrombocytopenia syndrome (SFTS) have made it an important threat to public health. Neutrophil extracellular traps (NETs) can be activated by a variety of pathogens and are associated with thrombocytopenia in viral infections. We aimed to identify NET production and its predictive value for disease progression and prognosis in patients with SFTS. Methods A prospective study was performed with a multicenter cohort of patients with SFTS (n = 112) to quantify serum NET levels. Three markers of NETs—namely, cell-free DNA (cfDNA), myeloperoxidase-DNA complexes, and lactoferrin-DNA complexes—were measured with PicoGreen double-stranded DNA assays and enzyme-linked immunosorbent assays. Receiver operating characteristic curves and multivariate regression analyses were performed to calculate the predictive value of cfDNA levels. Results SFTS was characterized by pronounced NET formation. The serum levels of NETs changed dynamically during disease progression, with an inverse pattern of the trends of platelet and neutrophil levels. High cfDNA levels were strongly associated with multiple pathological processes, including coagulopathy, myocardial damage, liver dysfunction, and the development of encephalopathy. A high level of cfDNA (&gt;711.7 ng/mL) at the time of the initial diagnosis predicted severe illness in patients with SFTS (odds ratio, 8.285 [95% confidence interval, 2.049–33.503]; P = .003). Conclusions This study has a high degree of clinical impact for identification of cfDNA as a useful predictive biomarker of clinical outcomes of SFTS.

As the coronavirus disease 2019 (COVID‐19) pandemic is still ongoing and severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) variants are circulating worldwide, an increasing number of breakthrough infections are being detected despite the good efficacy of COVID‐19 vaccines. Data on 88 COVID‐19 breakthrough cases (breakthrough infections group) and 41 unvaccinated cases (unvaccinated group) from June 1 to August 22, 2021, were extracted from a cloud database established at Beijing Ditan Hospital to evaluate the clinical, immunological, and genomic characteristics of COVID‐19 breakthrough infections. Among these 129 COVID‐19 cases, 33 whole genomes were successfully sequenced, of which 23 were Delta variants, including 15 from the breakthrough infections group. Asymptomatic and mild cases predominated in both groups, but two patients developed severe disease in the unvaccinated group. The median time of viral shedding in the breakthrough infections group was significantly lower than that in the unvaccinated group (p = 0.003). In the breakthrough infections group, the IgG titers showed a significantly increasing trend (p = 0.007), and the CD4 + T lymphocyte count was significantly elevated (p = 0.018). For people infected with the Delta variant in the two groups, no significant difference was observed in either the quantitative reverse‐transcription polymerase chain reaction results or viral shedding time. In conclusion, among vaccinated patients, the cases of COVID‐19 vaccine breakthrough infections were mainly asymptomatic and mild, IgG titers were significantly increased and rose rapidly, and the viral shedding time was shorter.