Human-to-human transmission of 2019-novel coronavirus (2019-nCoV) (preprint)

ABSTRACT

Background: On December 31, 2019, an outbreak of COVID-19 in humans was reported in Wuhan, and then spread fast to other provinces, China. We analyzed data from field investigations and genetic sequencing to describe the evidence and characteristics of human-to-human transmission in Guangdong Province. Methods: A confirmed COVID-19 case was defined if a suspected case was verified with positive of SARS-CoV-2 in throat swabs, nasal swabs, bronchoalveolar lavage fluid (BALF), or endotracheal aspirates by real-time reverse transcriptase polymerase chain reaction assay (RT-PCR) or genetic sequencing. Field investigations were conducted for each confirmed case. Clinical and demographic data of confirmed cases were collected from medical records. Exposure and travel history were obtained by interview. Results: A total of 1,151 confirmed cases were identified as of February 10, 2020 in Guangdong Province, China. Of them, 697 (60.1%) cases were from 234 cluster infections. Two hundred and fourteen (18.6%) were secondary cases, in which 144 cases were from family cluster infections. With the epidemic continuing, although familial cluster events were dominated, community cluster events increased with a nosocomial event. The whole genomes within the same family cluster infections were identical, and presented a few unique single nucleotide variants (SNVs) compared with SARS-CoV-2 identified on December 2019 in Wuhan. Conclusions: We observed evident human-to-human transmissions of SARS-CoV-2 in Guangdong, China. Although most of them were from family cluster infections, community and nosocomial infections were increasing. Our findings indicate that human-to-human transmission risks are transferring from family to community in Guangdong Province.