Comparison of Transmissibility of Coronavirus Between Symptomatic and Asymptomatic Patients: Reanalysis of the Ningbo COVID-19 Data

Abstract

Background Since the outbreak of the novel coronavirus disease (COVID-19) in December 2019, the coronavirus has spread all over the world at an unprecedented rate. The transmissibility of the coronavirus from asymptomatic patients to healthy individuals has received enormous attention. An important study using COVID-19 data from the city of Ningbo, China, was carried out to estimate and compare the transmission rates of the coronavirus by the symptomatic and asymptomatic patients. However, in the original analysis, the usual chi-square tests were unduly used for some contingency tables with small cell counts including zero, which may violate the assumptions for the chi-square test. Objective We reanalyze the data from the city of Ningbo with more appropriate statistical methods to draw more reliable and sound conclusions on the transmission rates of the coronavirus by the symptomatic and asymptomatic patients. Methods We excluded the cases associated with the super-spreader and adopted a more appropriate statistical method, including the permutation test and the Fisher exact test, to reanalyze the COVID-19 data from the city of Ningbo. Results After excluding the cases related to the super-spreader, the Fisher exact test yields a P value of .84, which indicates stronger evidence of no difference in the transmission rates compared with the original analysis. The odds ratio of the coronavirus transmission rates between the symptomatic and asymptomatic patients is 1.2 with a 95% confidence interval 0.5-2.8. Conclusions Through a more in-depth and comprehensive statistical analysis of the Ningbo data, we concluded that there is no difference in the transmission rates of coronavirus between symptomatic and asymptomatic patients.

An Incidental Diagnosis of SARS-CoV-2 Pneumonia With Magnetic Resonance Imaging

“…There is a great interest in the detection of SARS-CoV-2 infection in asymptomatic patients, as they can contribute to the viral spread with similar transmission rates as symptomatic patients [15]. There is numerous emerging evidence of patients affected by COVID-19 pneumonia who are asymptomatic or mildly symptomatic at the time of the diagnosis who show imaging features consistent with lung involvement, similarly to the case report we presented [16,17].…”

Current understanding of the surface contamination and contact transmission of SARS-CoV-2 in healthcare settings

“…Viral transmission by asymptomatic carriers has also been reported in many studies (Bai et al 2020 ; Hu et al 2020c ; Lavezzo et al 2020 ; Qian et al 2020b ; Rothe et al 2020 ; Tong et al 2020 ). Some investigations indicate transmission rates by asymptomatic patients are as high as symptomatic patients (Chen et al 2020 ; Yin and Jin 2020 ) while others estimate the rate as one third of that of symptomatic transmissions (Wu 2020 ). Indeed, there is no significant difference in viral load between asymptomatic and symptomatic groups (Zou et al 2020 ) while the asymptomatic group shed virus significantly longer than the symptomatic group (Long et al 2020 ).…”

Clinical characteristics and infectivity of asymptomatic carriers of SARS‑CoV‑2 (Review)

“…Chen et al ( 36 ) followed up and investigated 2,147 close contacts in Ningbo, Zhejiang, China, with a total infection rate of 6.15%, while there was no significant difference in the infection rate between the confirmed cases and asymptomatic cases (6.30 and 4.11%, respectively) ( 36 ). Concomitantly, Yin and Jin ( 37 ) analyzed the transmission rate of 157 symptomatic cases and 30 asymptomatic cases of COVID-19 and identified that there was no significant difference in the transmission rate between symptomatic and asymptomatic patients. However, none of these studies excluded pre-symptomatic patients in the incubation period.…”