ABSTRACT
Objective:To analyze a family clustering of coronavirus disease 2019 （COVID-19） associated with the exposure to an asymptomatic case， and to provide evidences of developing strategies for COVID-19 prevention. Methods:Epidemiological investigation was conducted on a COVID-19 family cluster （1 confirmed case and 2 asymptomatic cases）. The specimens of the cases were tested for 2019 novel coronavirus nucleic acid with real-time fluorescence quantitative polymerase chain reaction. Results:The clustering epidemic occurred in a family. Two asymptomatic cases B and C （B’s son） had Wuhan residential history. After arrival in Beijing on January 24， 2020， B stayed in his mother's house. One family member A （B’s mother） developed the disease on February 7， 2020， while the other two family members D and E （B’s wife and brother） did not develop the disease， and they were managed as close contacts. Conclusion:Thisfamily COVID-19 clustering is induced by the exposure to an asymptomatic case. Identification of asymptomatic cases is very important for the control of COVID-19 epidemic.
ABSTRACT
The majority of dengue virus infections are asymptomatic, which could potentially facilitate the transmission of dengue fever and increase the percentage of sever dengue fever manifestations. This cross-sectional study explored the sero-prevalence of dengue virus infection in Guangzhou to clarify the infection spectrum. In total, 2085 serum samples were collected from residents of 34 communities. All samples were selected from a 200,000-sample database holding serum collected from community residents living in Liwan and Yuexiu districts of Guangzhou between September 2013 and August 2015, and 17 to 28 individuals of each age group were chosen per month. Dengue immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies were tested by enzyme-linked immunosorbent assay. Symptomatic infected individuals were identified via follow-up questionnaires. Among 2085 serum samples, anti-dengue IgG and IgM positive rates were 11.80% and 3.98%, respectively. The IgG antibody positive rate increased with age and was higher in poorly educated people than in highly educated people and in married individuals than in single individuals. Approximately 96.71% of dengue virus infections and an estimated 13.68% of the whole population were asymptomatic. Such high asymptomatic-infection rates have an impact on the local spread of dengue fever. Stricter surveillance, such as a network of rapid diagnostic laboratories, screening of residents in the epidemic season, and other integrated control measures are necessary.