Epidemiological feature, viral shedding, and antibody seroconversion among asymptomatic SARS-CoV-2 carriers and symptomatic/presymptomatic COVID-19 patients.

BACKGROUND: Novel coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is pandemic. However, data concerning the epidemiological features, viral shedding, and antibody dynamics between asymptomatic SARS-CoV-2 carriers and COVID-19 patients remain controversial. METHODS: We enrolled 193 SARS-CoV-2 infected subjects in Ningbo and Zhoushan, Zhejiang, China, from January 21 to March 6, 2020. All subjects were followed up to monitor the dynamics of serum antibody immunoglobulin M (IgM) and IgG against SARS-CoV-2 using colloidal gold-labeled and enzyme-linked immunosorbent assays. RESULTS: Of those, 31 were asymptomatic SARS-CoV-2 carriers, 148 symptomatic COVID-19 patients, and 14 presymptomatic COVID-19 patients. Compared to symptomatic COVID-19 patients, asymptomatic carriers were younger and had higher levels of white blood cell and lymphocyte, lower level of C-reactive protein, and shorter viral shedding duration. Conversion of IgM from positive to negative was shorter in asymptomatic carriers than in COVID-19 patients (7.5 vs. 25.5 days, P = 0.030). The proportion of those persistently seropositive for IgG against SARS-CoV-2 was higher in COVID-19 patients than in asymptomatic carriers (66.1% vs. 33.3%, P = 0.037). Viral load was higher in symptomatic patients than presymptomatic patients (P = 0.003) and asymptomatic carriers (P = 0.004). Viral shedding duration was longer in presymptomatic COVID-19 patients than in asymptomatic carriers (48.0 vs. 24.0 days, P = 0.002). Asymptomatic carriers acquired infection more from intra-familial transmission than did COVID-19 patients (89.0% vs. 61.0%, P = 0.028). In 4 familial clusters of SARS-CoV-2 infection, asymptomatic carriers were mainly children and young adults while severe COVID-19 was mainly found in family members older than 60 years with comorbidities. CONCLUSION: Asymptomatic carriers might have a higher antiviral immunity to clear SARS-CoV-2 than symptomatic COVID-19 patients and this antiviral immunity should be contributable to innate and adaptive cellular immunity rather than humoral immunity. The severity of COVID-19 is associated with older age and comorbidities in familial clustering cases.

Replication capacity and adaptability of a severe fever with thrombocytopenia syndrome virus at different temperatures.

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging disease caused by the SFTS virus (SFTSV). Although fever and thrombocytopenia are the typical manifestations of SFTS, a specific SFTS case with no fever was observed in Zhejiang, China. In this report, we aimed to explore the probable reason for the absence of fever by analyzing the genetic characteristics and temperature sensitivity (ts) of the SFTSV strain ZJ2013-06, which was isolated from the specific case. Phylogenetically, different clusters of SFTSV strains circulated in Zhejiang. ZJ2013-06 was farthest from ZJ2014-02, an isolate belonging to a Chinese dominant cluster, and nearest to the coastal strain NB24/CHN/2013. Ts tests, performed on Vero cells at 37°C and 39°C, indicated that ZJ2013-06 had restricted replication at 39°C. Its viral loads were substantially reduced at 39°C compared with that at 37°C (approximately 100-fold reduction) and were significantly lower than that of ZJ2014-02 at 39°C (P < 0.01). By adaptive culture at 39°C, the induced strain ZJ2013-06-P7 was obtained. Owing to a reverse mutation (S1616), ZJ2013-06-P7 lost the ts of the original strain, displaying similar replication processes with NB24/CHN/2013. The results indicated that the amino acid residue 1616 was related to the ts characteristics of ZJ2013-06. Our study revealed that ZJ2013-06 was temperature-sensitive and may be related to the absence of fever in our case.

Power-ratio tunable dual-wavelength laser using linearly variable Fabry-Perot filter as output coupler.

For a linearly variable Fabry-Perot filter, the peak transmission wavelengths change linearly with the transverse position shift of the substrate. Such a Fabry-Perot filter is designed and fabricated and used as an output coupler of a c-cut Nd:YVO4 laser experimentally in this paper to obtain a 1062 and 1083 nm dual-wavelength laser. The peak transmission wavelengths are gradually shifted from 1040.8 to 1070.8 nm. The peak transmission wavelength of the Fabry-Perot filter used as the output coupler for the dual-wavelength laser is 1068 nm and resides between 1062 and 1083 nm, which makes the transmissions of the desired dual wavelengths change in opposite slopes with the transverse shift of the filter. Consequently, powers of the two wavelengths change in opposite directions. A branch power, oppositely tunable 1062 and 1083 nm dual-wavelength laser is successfully demonstrated. Design principles of the linear variable Fabry-Perot filter used as an output coupler are discussed. Advantages of the method are summarized.

A case of severe fever with thrombocytopenia syndrome caused by a novel bunyavirus in Zhejiang, China.

Two typical symptoms of severe fever with thrombocytopenia syndrome (SFTS) are fever and thrombocytopenia. Here we report a laboratory confirmed SFTS case with no fever during the entire hospitalization period, in Daishan County, Zhejiang Province, China. A 77-year-old woman was admitted to hospital with symptoms including nausea, retching, and anorexia. Laboratory tests revealed thrombocytopenia, leukopenia, and liver and brain damage. The case was later confirmed as a novel bunyavirus infection. Epidemiological investigations revealed that she had no history of tick bites or skin damage, and no known exposure to persons with a similar illness in the area prior to illness onset. The patient was hospitalized for 15 days, and during the whole admission period, she did not experience any fever. The patient recovered and was discharged.

Characterization of severe fever with thrombocytopenia syndrome in rural regions of Zhejiang, China.

Severe fever with thrombocytopenia syndrome virus (SFTSV) infections have recently been found in rural regions of Zhejiang. A severe fever with thrombocytopenia syndrome (SFTS) surveillance and sero-epidemiological investigation was conducted in the districts with outbreaks. During the study period of 2011-2014, a total of 51 SFTSV infection cases were identified and the case fatality rate was 12% (6/51). Ninety two percent of the patients (47/51) were over 50 years of age, and 63% (32/51) of laboratory confirmed cases occurred from May to July. Nine percent (11/120) of the serum samples from local healthy people without symptoms were found to be positive for antibodies to the SFTS virus. SFTSV strains were isolated by culture using Vero, and the whole genomic sequences of two SFTSV strains (01 and Zhao) were sequenced and submitted to the GenBank. Homology analysis showed that the similarity of the target nucleocapsid gene from the SFTSV strains from different geographic areas was 94.2-100%. From the constructed phylogenetic tree, it was found that all the SFTSV strains diverged into two main clusters. Only the SFTSV strains from the Zhejiang (Daishan) region of China and the Yamaguchi, Miyazakj regions of Japan, were clustered into lineage II, consistent with both of these regions being isolated areas with similar geographic features. Two out of eight predicted linear B cell epitopes from the nucleocapsid protein showed mutations between the SFTSV strains of different clusters, but did not contribute to the binding ability of the specific SFTSV antibodies. This study confirmed that SFTSV has been circulating naturally and can cause a seasonal prevalence in Daishan, China. The results also suggest that the molecular characteristics of SFTSV are associated with the geographic region and all SFTSV strains can be divided into two genotypes.

[Identification of genotype III Japanese encephalitis virus isolated in Zhejiang province].

OBJECTIVE: To investigate the molecular characteristics and genotype of Japanese encephalitis virus (JEV) found in vector mosquitoes in Zhejiang province from 1982 to 1983. METHODS: A total of 3188 mosquitoes were collected in Dinghai district and Yiwu city in Zhejiang province, during year 1982 and 1983. The virus was isolated by C6/36 cell, and then identified by hemagglutination inhibition test. The isolated strains were activated in year 2011, and plaque forming unit (PFU) were applied to test the virus titer. The suckling rats were tested under intracranial inoculation, where PrM and E genes were amplified and sequenced. Their nucleotide and amino acid sequences were analyzed and compared with the JEV vaccine strain SA14-14-2 and the JEV isolated in Zhejiang province during 2007 and 2010; and phylogenetic tree were constructed by bioinformatic software. RESULTS: From the 3188 mosquitoes captured, eleven virus strains were isolated and found to be able to cause cytopathogenic effect (CPE) in C6/36 cells within 72 hours. Virus titer ranged from 2.5 to 6.47 lg PFU/ml. The suckling rats would die within 72 hours since the inoculation. The phylogenetic analysis with the PrM and E genes showed that the JEV isolated in Zhejiang during 1982 and 1983 belonged to genotype III; while the JEV isolated in Zhejiang during 2007 and 2010 belonged to genotype I. The analysis of E genes from 5 isolated strains found that the homology of nucleotide sequence was over 98.9%, and the homology of amino acid sequence was over 99.8%. The compare between the 5 virus strains and the vaccine strain SA14-14-2 found 10 common amino acid variation sites, and showed that the homology of nucleotide sequence was over 97.7%, and the homology of amino acid sequence was 99.2%. The compare between the 5 virus strains and the JEV isolated in Zhejiang during 2007 and 2010 found a 87.7% - 87.9% nucleotide homology and an over 98.8% amino acid homology. CONCLUSION: The JEV isolated from the mosquitoes in Dinghai district and Yiwu city between year 1982 and 1983, were genotype III.