Epidemiologic Characteristics of COVID-19 in Guizhou, China

At the end of 2019, a coronavirus disease 2019 (COVID-19) outbroke in Wuhan, China, and spread to Guizhou province on January of 2020. To acquire the epidemiologic characteristics of COVID-19 in Guizhou, China, we collected data on 162 laboratory-confirmed cases related to COVID-19. We described the demographic characteristics of the cases and estimated the incubation period, serial interval and basic reproduction number. We also presented two representative case studies in Guizhou province -- Case Study 1 was an example of asymptomatic carrier; and Case Study 2 was an example of a large and complex infection chain that involved four different districts spanning three provinces and eight families. With an estimation of 8 days incubation period and 6 days serial interval, our results indicate that there may exist infectiousness during the incubation period for 2019-nCoV. This increases the difficulty of screening or identifying cases related to COVID-19.

"fever and/or symptoms in respiratory system; radiographic evidence of pneumonia; 46 low or normal white-cell count or low lymphocyte count." 8 Epidemiologic histories must fit at least 1 of 4 following criteria: "A history of traveling Hubei Province or 48 other districts that has confirmed cases reported within 14 days of symptom onset; A 49 history of contacting with patient who has fever or symptoms in respiratory system 50 from Hubei Province or other districts that has confirmed cases reported within 14 51 days of symptom onset; Any person who has had a close contact with confirmed 52 cases; cluster cases." 8 With a stricter definition, Guizhou Health Committee counted 53 all cases that fit clinical characteristics criteria but not any criteria of epidemiologic 54 histories described above as suspected cases. A confirmed case was defined as a case 55 with respiratory specimens that tested positive for the 2019-nCoV by at least one of 56 the following two methods: positive result by real-time reverse-transcription-57 polymerase-chain-reaction (RT-PCR) assay for 2019-nCoV or a genetic sequence that 58 matches 2019-nCoV. Asymptomatic carrier (i.e. case that displays no signs or 59 symptoms to 2019-nCoV) was not announced by Health Committee officially, but 60 was included in this study.   to acquire the accurate onset date, and as the confirmation date for confirmed cases 92 All rights reserved. No reuse allowed without permission. the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

Sources of Data
The copyright holder for this preprint (which was not peer-reviewed) is . https://doi.org/10.1101/2020.03.01.20028944 doi: medRxiv preprint without symptoms. As the date of infecting exposure for a given individual falls 93 within a finite interval, an exposure window was clarified to denote this interval.

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Criteria of infecting exposure was described above in the Case Definitions section. This study provides an initial analysis among epidemiologic characteristics 145 and two typical transmission phenomena of COVID-19. Most index cases were 146 exposed to Wuhan or confirmed cases related to Wuhan, but it is also necessary to  In addition to the evidence of the human-to-human transmission, it is likely 153 that there exists infectiousness to some extend during the incubation period, and the 154 presence of "super-spreaders". The median incubation period was 8.2 days (95% CI: 155 7.9 -9.5) in our study, which is longer than a recent report of 425 patients (8.2 days 156 vs. 5.2 days), this may be a results of recall bias, during epidemiological investigation, symptoms does not yet infect others, which assumes that all index cases should show 165 symptoms before their secondary cases. However, as the investigation went on, 166 Guizhou CDC found that there existed index cases who showed symptoms after that 167 of their secondary cases. This may lead to that the estimated R0 was not robust as we 168 do not hold enough evidence and information to the presence of asymptomatic carrier, 169 those data were not included in the estimation model.    the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

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The horizontal axis represents the onset date of confirmed cases or suspected cases.

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The onset data was defined as the self-reported first date to have symptoms related to 249 2019-nCoV and as the confirmation date for confirmed cases without symptoms. On 250 January 21, the first case was officially confirmed and reported by Guiyang (capital 251 city of Guizhou) CDC, whose onset date was on January 9th when the case was still in 252 All rights reserved. No reuse allowed without permission. the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.
The copyright holder for this preprint (which was not peer-reviewed) is   the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.
The copyright holder for this preprint (which was not peer-reviewed) is   the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.
The copyright holder for this preprint (which was not peer-reviewed) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.