Coronavirus Disease 2019 (COVID-19) is a deadly emerging infectious disease caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Because SARS-CoV-2 is easily transmitted through the air and has a relatively long incubation time, COVID-19 has rapidly developed into a global pandemic. As there are no antiviral agents for the prevention and treatment of this severe pathogen except for remdesivir, development of antiviral therapies to treat infected individuals remains highly urgent. Here, we showed that baicalein and baicalin exhibited significant antiviral activity against SARS-CoV-2, the causative agent of COVID-19 through in vitro studies. Our data through cell-based and biochemical studies showed that both compounds act as SARS-CoV-2 RNA-dependent RNA polymerase (RdRp) inhibitors directly and inhibit the activity of the SARS-CoV-2 RdRp, but baicalein was more potent. We also showed specific binding of baicalein to the SARS-CoV-2 RdRp, making it a potential candidate for further studies towards therapeutic development for COVID-19 as a selective non-nucleoside polymerase inhibitor.
Dengue is a rapidly spreading mosquito-borne disease caused by the dengue virus (DENV) and has emerged as a severe public health problem around the world. Guangdong, one of the southern Chinese provinces, experienced a serious outbreak of dengue in 2014, which was believed to be the worst dengue epidemic in China over the last 20 years. To better understand the epidemic, we collected the epidemiological data of the outbreak and analyzed 14,594 clinically suspected dengue patients from 25 hospitals in Guangdong. Dengue cases were then laboratory-confirmed by the detection of DENV non-structural protein 1 (NS1) antigen and/or DENV RNA. Afterwards, clinical manifestations of dengue patients were analyzed and 93 laboratory-positive serum specimens were chosen for the DENV serotyping and molecular analysis. Our data showed that the 2014 dengue outbreak in Guangdong had spread to 20 cities and more than 45 thousand people suffered from dengue fever. Of 14,594 participants, 11,387 were definitively diagnosed. Most manifested with a typical non-severe clinical course, and 1.96 % developed to severe dengue. The strains isolated successfully from the serum samples were identified as DENV-1. Genetic analyses revealed that the strains were classified into genotypes I and V of DENV-1, and the dengue epidemic of Guangdong in 2014 was caused by indigenous cases and imported cases from the neighboring Southeast Asian countries of Malaysia and Singapore. Overall, our study is informative and significant to the 2014 dengue outbreak in Guangdong and will provide crucial implications for dengue prevention and control in China and elsewhere.