Risk factors associated with PCR repositivity in patients with COVID-19 after recovery in Guangzhou, China: a retrospective cohort study (preprint)

Some patients retested positive for SARS-CoV-2 following negative testing results and discharge. However, the potential risk factors associated with redetectable positive test results in a large sample of patients who recovered from COVID-19 have not been well estimated. A total of 745 discharged COVID-19 patients were enrolled between January 30, 2020, and September 9, 2020, in Guangzhou, China. Data on the clinical characteristics, comorbidities, drug therapy, RT-PCR testing, and contact modes to close contacts were collected. Patients who tested positive for SARS-CoV-2 after discharge (positive retest patients) were confirmed by guidelines issued by China. The repositive rate in different settings was calculated. Among 745 discharged patients, 157 (21.1%; 95% CI, 18.2% to 24.0%) retested positive, of which 55 (35.0%) were asymptomatic, 15 (9.6%) had mild symptoms, 83 (52.9%) had moderate symptoms and 4 (2.6%) had severe symptoms at the first admission. The median time from discharge to repositivity was 8.0 days (IQR, 8.0 to 14.0 days). Most positive retest patients were without clinical symptoms, and lymphocyte cell counts were higher than before being discharged. The likelihood of repositive testing for SARS-CoV-2 RNA was significantly higher among patients who were younger age (OR, 3.88; 95% CI, 1.74 to 8.66, 0 to 17 years old), had asymptomatic severity (OR, 4.36; 95% CI, 1.47 to 12.95) and did not have clinical symptoms (OR, 1.89; 95% CI, 1.32 to 2.70, without fever). We found that the positive retest rate of COVID-19 was relatively high, and these patients tested positive again with a median of 8.0 to 14.0 days after discharge. Positive retest results were mainly observed in young patients without severe clinical symptoms. These findings suggest that a significant proportion of patients could carry viral fragments for a long time, and effective management, such as a prolonged quarantine phase for discharged patients, is necessary.

Air and surface contamination in non-health care settings among 641 environmental specimens of 39 COVID-19 cases (preprint)

BackgroundLittle is known about the SARS-CoV-2 contamination of environmental surfaces and air in non-health care settings among COVID-19 cases. Methods and findingsWe explored the SARS-CoV-2 contamination of environmental surfaces and air by collecting air and swabbing environmental surfaces among 39 COVID-19 cases in Guangzhou, China. The specimens were tested by RT-PCR testing. The information collected for COVID-19 cases included basic demographic, clinical severity, onset of symptoms, radiological testing, laboratory testing and hospital admission. A total of 641 environmental surfaces and air specimens were collected among 39 COVID-19 cases before disinfection. Among them, 20 specimens (20/641, 3.1%) were tested positive from 9 COVID-19 cases (9/39, 23.1%), with 5 (5/101, 5.0%) positive specimens from 3 asymptomatic cases, 5 (5/220, 2.3%) from 3 mild cases, and 10 (10/374, 2.7%) from 3 moderate cases. All positive specimens were collected within 3 days after diagnosis, and 10 (10/42, 23.8%) were found in toilet (5 on toilet bowl, 4 on sink/faucet/shower, 1 on floor drain), 4 (4/21, 19.0%) in anteroom (2 on water dispenser/cup/bottle, 1 on chair/table, 1 on TV remote), 1 (1/8, 12.5%) in kitchen (1 on dining-table), 1 (1/18, 5.6%) in bedroom (1 on bed/sheet pillow/bedside table), 1 (1/5, 20.0%) in car (1 on steering wheel/seat/handlebar) and 3 (3/20, 21.4%) on door knobs. Air specimens in room (0/10, 0.0%) and car (0/1, 0.0%) were all negative. ConclusionsSARS-CoV-2 was found on environmental surfaces especially in toilet, and could survive for several days. We provided evidence of potential for SARS-CoV-2 transmission through contamination of environmental surfaces.

Current situation and improvement suggestions of COVID-19 close contacts tracking investigation official letter management (preprint)

Background: This study analyzes the current status of tracking investigation official letter management for 9036 COVID-19 close contacts in Guangzhou,and explains the necessity of establishing a COVID-19 close contacts tracking investigation sharing system. Method: Based on the information obtained from COVID-19's close contacts' tracking investigation official letters from January 21 to March 31 in Guangzhou, the epidemic situation map and flow chart of receiving and sending official letters were drawn, and the observation rate, sampling rate and Turn positive rate of close contacts were calculated. Results: The tracking investigation official letter involved in 31 provinces (municipalities directly under the central government, autonomous regions) and 172 cities, investigation close contacts with 9036: 309 investigation letters were received from the nonlocal case, investigation close contacts with 2790, involved in 30 provinces and 95 cities, medical observation at a rate of 100%, sampling rate 99.56%, turn positive rate was 3.76%; The city of Guangzhou issued 204 official letters of investigation, with 6,246 close contacts, covering 27 provinces and 114 cities. The medical observation rate was 100%, the sampling rate 99.63%, and turn the positive rate of 2.26%. The reply time of the investigation results is within 1-12 hours, and the other 1-3 days. As of March 31, 440 cases of covid-19 were confirmed in Guangzhou (including 92 imported cases), and the tracking coefficient of close contacts was 14.2 (6246 / 440). Conclusion: Guangzhou close contacts tracking investigation official letter management is tight, the prompt detection of the source of infection to control the epidemic situation is significant. However, due to the multiple sources and complicated process of official letters, it is suggested to establish a COVID-19 close contacts tracking and investigation sharing system.

Household Secondary Attack Rate of COVID-19 and Associated Determinants (preprint)

Background: As of April 2, 2020, the global reported number of COVID-19 cases has crossed over 1 million with more than 55,000 deaths. The household transmissibility of SARS-CoV-2, the causative pathogen, remains elusive. Methods: Based on a comprehensive contact-tracing dataset from Guangzhou, we estimated both the population-level effective reproductive number and individual-level secondary attack rate (SAR) in the household setting. We assessed age effects on transmissibility and the infectivity of COVID-19 cases during their incubation period. Results: A total of 195 unrelated clusters with 212 primary cases, 137 nonprimary (secondary or tertiary) cases and 1938 uninfected close contacts were traced. We estimated the household SAR to be 13.8% (95% CI: 11.1-17.0%) if household contacts are defined as all close relatives and 19.3% (95% CI: 15.5-23.9%) if household contacts only include those at the same residential address as the cases, assuming a mean incubation period of 4 days and a maximum infectious period of 13 days. The odds of infection among children (<20 years old) was only 0.26 (95% CI: 0.13-0.54) times of that among the elderly ([≥]60 years old). There was no gender difference in the risk of infection. COVID-19 cases were at least as infectious during their incubation period as during their illness. On average, a COVID-19 case infected 0.48 (95% CI: 0.39-0.58) close contacts. Had isolation not been implemented, this number increases to 0.62 (95% CI: 0.51-0.75). The effective reproductive number in Guangzhou dropped from above 1 to below 0.5 in about 1 week. Conclusion: SARS-CoV-2 is more transmissible in households than SARS-CoV and MERS-CoV, and the elderly [≥]60 years old are the most vulnerable to household transmission. Case finding and isolation alone may be inadequate to contain the pandemic and need to be used in conjunction with heightened restriction of human movement as implemented in Guangzhou.

Modes of contact and risk of transmission in COVID-19 among close contacts (preprint)

Background Rapid spread of SARS-CoV-2 in Wuhan prompted heightened surveillance in Guangzhou and elsewhere in China. Modes of contact and risk of transmission among close contacts have not been well estimated. Methods We included 4950 closes contacts from Guangzhou, and extracted data including modes of contact, laboratory testing, clinical characteristics of confirmed cases and source cases. We used logistic regression analysis to explore the risk factors associated with infection of close contacts. Results Among 4950 closes contacts, the median age was 38.0 years, and males accounted for 50.2% (2484). During quarantine period, 129 cases (2.6%) were diagnosed, with 8 asymptomatic (6.2%), 49 mild (38.0%), and 5 (3.9%) severe to critical cases. The sensitivity of throat swab was 71.32% and 92.19% at first to second PCR test. Among different modes of contact, household contacts were the most dangerous in catching with infection of COVID-19, with an incidence of 10.2%. As the increase of age for close contacts and severity of source cases, the incidence of COVID-19 presented an increasing trend from 1.8% (0-17 years) to 4.2% (60 or over years), and from 0.33% for asymptomatic, 3.3% for mild, to 6.2% for severe and critical source cases, respectively. Manifestation of expectoration in source cases was also highly associated with an increased risk of infection in their close contacts (13.6%). Secondary cases were in general clinically milder and were less likely to have common symptoms than those of source cases. Conclusions In conclusion, the proportion of asymptomatic and mild infections account for almost half of the confirmed cases among close contacts. The household contacts were the main transmission mode, and clinically more severe cases were more likely to pass the infection to their close contacts. Generally, the secondary cases were clinically milder than those of source cases.

Early Prediction of Disease Progression in 2019 Novel Coronavirus Pneumonia Patients Outside Wuhan with CT and Clinical Characteristics (preprint)

Objective: To determine the predictive value of CT and clinical characteristics for short-term disease progression in patients with 2019 novel coronavirus pneumonia (NCP). Materials and Methods: 224 patients with confirmed 2019 novel coronavirus (COVID-19) infection outside Wuhan who had chest CT examinations were retrospectively screened. Clinical data were obtained from electronic medical records. CT images were reviewed and scored for lesion distribution, lobe and segment involvement, ground-glass opacities, consolidation, and interstitial thickening. All included patients with moderate NCP were observed for at least 14 days from admission to determine whether they exacerbated to severe NCP (progressive group) or not (stable group). CT and clinical characteristics between the two groups were compared, and multivariate logistic regression and sensitivity analyses were performed to identify the risk factors for developing severe NCP. Results: A total of 141 patients with moderate NCP were included, of which 15 (10.6%) patients developed severe NCP during hospitalization and assigned to the progressive group. Multivariate logistic regression analysis showed that higher neutrophil-to-lymphocyte ratio (NLR) (odds ratio [OR] and 95% confidence interval [CI], 1.26 [1.04-1.53]; P = 0.018) and CT severity score (OR and 95% CI, 1.25 [1.08-1.46]; P = 0.004) on admission were independent predictors for progression to severe NCP, and sensitivity analysis confirmed the consistent results in nonimported patients but not in imported patients. However, no significant difference in lung involvement was found on CT between imported and nonimported patients (all P > 0.05). Patients who were admitted more than 4 days from symptom onset tended to have more severe lung involvement. Spearman correlation analysis showed the close association between CT severity score and inflammatory indexes (r = 0.17~0.47, all P < 0.05). Conclusion: CT severity score was associated with inflammatory levels and higher NLR and CT severity score on admission were independent risk factors for short-term progression in patients with NCP outside Wuhan. Furthermore, early admission and surveillance by CT should be recommended to improve clinical outcomes.