Background The coronavirus disease 2019 (COVID-19), caused by infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been rapidly spreading nationwide and abroad. A serologic test to identify antibody dynamics and response to SARS-CoV-2 was developed. Methods The antibodies against SARS-CoV-2 were detected by an enzyme-linked immunosorbent assay based on the recombinant nucleocapsid protein of SARS-CoV-2 in patients with confirmed or suspected COVID-19 at 3–40 days after symptom onset. The gold standard for COVID-19 diagnosis was nucleic acid testing for SARS-CoV-2 by real-time reverse-transcription polymerase chain reaction (rRT-PCR). The serodiagnostic power of the specific immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies against SARS-CoV-2 was investigated in terms of sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and consistency rate. Results The seroconversion of specific IgM and IgG antibodies were observed as early as the fourth day after symptom onset. In the patients with confirmed COVID-19, sensitivity, specificity, PPV, NPV, and consistency rate of IgM were 77.3% (51/66), 100%, 100%, 80.0%, and 88.1%, respectively, and those of IgG were 83.3% (55/66), 95.0%, 94.8%, 83.8%, and 88.9%. In patients with suspected COVID-19, sensitivity, specificity, PPV, NPV, and consistency rate of IgM were 87.5% (21/24), 100%, 100%, 95.2%, and 96.4%, respectively, and those of IgG were 70.8% (17/24), 96.6%, 85.0%, 89.1%, and 88.1%. Both antibodies performed well in serodiagnosis for COVID-19 and rely on great specificity. Conclusions The antibodies against SARS-CoV-2 can be detected in the middle and later stages of the illness. Antibody detection may play an important role in the diagnosis of COVID-19 as a complementary approach to viral nucleic acid assays.

BackgroundThe novel coronavirus (SARS-CoV-2) infected over 3,300 health-care-workers (HCWs) in early 2020 in China. Little information is known about nosocomial infections of HCWs in the initial period. We analyzed data from HCWs with nosocomial infections in Wuhan Union Hospital and their family members. MethodsWe collected and analyzed data on exposure history, illness timelines, and epidemiologic characteristics of 25 laboratory-confirmed and two highly suspected HCWs as well as ten of their family members with COVID-19 from Jan 5 to Feb 12, 2020. Among them, demographics and clinical features of the 35 laboratory-confirmed cases were investigated and viral RNA of 12 cases was sequenced and analyzed. ResultsNine clusters were found among the patients. All patients showed mild to moderate clinical manifestation and recovered without deterioration. The average periods of incubation, clinical onset serial interval (COSI), and virus shedding were 4.5 days, 5.2 ± 3.2 days, and 18.5 days, respectively. Complete genomic sequences of 12 different coronavirus strains demonstrated that the viral structure with small, irrelevant mutations was stable in the transmission chains and showed remarkable traits of infectious traceability. ConclusionsSARS-CoV-2 can be rapidly transmitted person-to-person regardless of whether they have symptoms in both hospital settings and social activities based on the short period of incubation and COSI. The public health service should take practical measures to curb the spread, including isolation of cases, tracing close-contacts, and containment of severe epidemic areas. Besides, the HCWs should be alert during the epidemic, and make self-quarantine if self-suspected. Nosocomial Outbreak of 2019 Novel

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