key: cord-0998204-27g7667g authors: Samaddar, Arghadip; Gadepalli, Ravisekhar; Nag, Vijaya Lakshmi; Misra, Sanjeev; Bhardwaj, Pankaj; Singh, Pankaj; Meena, Mahadev; Sharma, Prem Prakash; Grover, Malika; Garg, Mahendra Kumar; Chauhan, Nishant; Dutt, Naveen; Niwas, Ram; Kumar, Deepak; Sharma, Praveen; Goel, Akhil Dhanesh; Kumar Gupta, Manoj; Saurabh, Suman; Rai, Shubham; Lawdiya, Chunnilal; Saini, Jinesh; Singh, Deepak title: Viral RNA Shedding and Transmission Potential of Asymptomatic and Pauci-symptomatic COVID-19 Patients date: 2020-12-08 journal: Open Forum Infect Dis DOI: 10.1093/ofid/ofaa599 sha: 0bd54a7081861253deb21ba9cb75fdf00e8ccb0c doc_id: 998204 cord_uid: 27g7667g We studied the pattern and duration of viral RNA shedding in 32 asymptomatic and 11 pauci-symptomatic coronavirus disease 2019 (COVID-19) cases. Viral RNA shedding in exhaled breath progressively diminished and became negative after six days of a positive reverse transcription polymerase chain reaction (RT-PCR) test. Therefore, the duration of isolation can be minimised to six days. The transmission dynamics of coronavirus disease 2019 (COVID -19) has been extensively studied in symptomatic individuals. However, as the outbreak progressed, it became evident that many cases are asymptomatic having infectivity same as symptomatic infections [1, 2] . Several studies have shown that the chances of asymptomatic infections are increased in crowded and family-clustered settings [3, 4] , which is a matter of concern for densely populated countries where isolation is difficult to achieve. Viral load is another contributory factor determining infectivity [5, 6] . Studies have shown that viral load in asymptomatic individuals can be same as symptomatic patients, indicating that people without obvious symptoms can potentially transmit the infection [7] . The transmission dynamics of COVID-19 in asymptomatic and pauci-symptomatic individuals is poorly understood. The present study aimed to analyse the pattern, duration and trends of viral RNA shedding in nasopharyngeal (NP) secretions and exhaled breath of asymptomatic and pauci-symptomatic secondary cases of COVID-19. These findings might help in strengthening the effectiveness of COVID-19 control measures and thus, limit the spread of the disease. This was a prospective observational time-to-event study in which 44 participants, above 18 years of age, who had known history of contact with symptomatic COVID-19 cases and tested positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), were enrolled. They were traced within 24 hours of contact and tested by reverse transcription polymerase chain reaction (RT-PCR). Accordingly, the day of contact was considered as Day 0 and the day of positive RT-PCR test result was considered as Day 1. All positive contacts were isolated in designated community quarantine facility and carefully monitored till two consecutive negative RT-PCR results were obtained at least 24 hours apart. Any participant developing symptomatic illness during the period was shifted to COVID-19 ward of All India Institute of Medical Sciences, Jodhpur, and excluded from the study. Written informed consent was obtained from each participant after approval by the institute's Ethics Committee (Ref. no. AIIMS/IEC/2020-21/3034). The cases were classified as asymptomatic and paucisymptomatic based on the definitions set by the WHO [8] and Rivett et al. [9] (see Supplementary Table 1 for more details on case definitions). The participants were instructed to wear a single mask for the whole day. Nasopharyngeal (NP) swab and corresponding day's mask were collected from each participant and tested for SARS-CoV-2 RNA by RT-PCR, using primer and probe sequences described by Corman et al [10] (Collection and transport of specimens and PCR protocol are described in detail in the Supplementary Data). The cycle threshold (Ct) values for NP swabs and masks of respective days were calculated and analysed using test of normality by Kolmogorov-Smirnov and Shapiro-Wilk tests. Since all the data was not found to follow normal distribution, non-parametric tests were used. For comparison of repeated measures, Friedman chi-square test was used to test the significance between the Ct values over the days. Further, to observe the significance between two paired data, Wilcoxon-Mann-Whitney rank test was used and p<0.01 was used as level of significance. The association between the median Ct values was calculated using Spearman Rank correlation coefficient. Statistical analysis was performed using IBM SPSS version 20.0 (IBM Corp., Armonk, NY). Out of 44 participants, 32 (73%) were asymptomatic and 11 (25%) were pauci-symptomatic. One participant turned symptomatic during the course of study and was excluded from evaluation. Thirty six (82%) cases were males and 8 (18%) were females. Asymptomatic and pauci-symptomatic cases were more common in <50 years age group comprising 72% of the total cases (42% in 30-50 years age group followed by 30% in 18-30 years age group), while 16% and 12% of the cases belonged to 50-60 years and > 60 years age groups, respectively. In pauci-symptomatic cases, non-persistent cough was the commonest symptom (8/11, 73%). Other symptoms included sore throat, myalgia, headache, respiratory distress, and fatigue. Thirteen (30%) patients had underlying co-morbidities, such as, hypertension (9/43; 21%), type 2 diabetes mellitus (5/43; 12%), and asthma, ischemic heart disease and cholelithiasis (1/43; 2% each). The co-morbid conditions were more commonly observed in males (12/ Our results suggest a likelihood of transmission of SARS-CoV-2 through exhaled breath of asymptomatic and pauci-symptomatic cases during the first six days after a positive RT PCR test, with the day of positive test being Day 1. So far, very few studies have demonstrated the degree and duration of SARS-CoV-2 shedding in asymptomatic and pauci-symptomatic cases [11, 12] . The present study is the first to have documented detection of SARS-CoV-2 RNA in exhaled air (masks), and correlated the degree and duration of viral RNA shedding between NP swabs and masks worn on respective days. Previous studies have shown that asymptomatic and pauci-symptomatic cases occur in all age groups from infants [13, 14] to middle-aged adults [15] and even the elderly [16] . According to Hu et al. [15] , asymptomatic cases were relatively young, with a median age of 14 years. In the present study, we observed that adults between 18 to 50 years of age accounted for majority (72%) of the asymptomatic cases, which is a matter of concern as this age group predominantly comprises the working population who are more likely to travel frequently and thus, more chances of transmitting the infection to healthy contacts. shedding can be variable. Zhou et al. [6] observed that asymptomatic patients have a lower viral load than symptomatic ones and the mean duration of viral shedding in asymptomatic cases was seven days. However, another study showed no difference in viral load between asymptomatic and symptomatic individuals with viral shedding detected till Day 11 after contact [15] . Sia et al. [17] reported that hamsters infected with SARS-CoV-2 could transmit the infection to healthy hamsters on Day 1 after infection, but not on Day 6. In the present study, we observed that viral RNA shedding in both NP swabs and exhaled breath progressively diminished over time, becoming undetectable in the latter after Day 6. Also, a significant positive correlation was observed between the viral RNA shedding in NP swabs and masks for six days. These findings suggest that though NP swabs of asymptomatic and pauci-symptomatic cases test positive till Day 9, they shed the virus in exhaled breath and are likely to transmit the infection to contacts during the first six days after a positive test. According to the current estimates, asymptomatic cases comprise 4%−41% of the total cases [18] . These cases most often go unnoticed until some of their family members or close contacts develop symptomatic illness. Hence, to avoid missing infected individuals, it is essential to screen all close contacts of confirmed or suspected cases. RT-PCR of NP swabs remains the mainstay of diagnosis of COVID-19. However, mere detection of SARS-CoV-2 RNA in clinical specimens is not a measure of infectivity and does not necessarily mean that the person is infectious [8, 19] . For the virus to be infective, it should be capable of replicating efficiently in cultured cells. However, virus culture requires specialised laboratory and may be less sensitive than RT-PCR. In the present study, we observed a constant decrease in viral shedding over time with no detectable viral RNA in exhaled breath after six days of a positive RT-PCR test. Based on these findings, it would be prudent to curtail the quarantine duration of asymptomatic and pauci-symptomatic individuals to six days, which would remove the 8 unnecessary long periods of isolation, affecting individual well-being, society and access to healthcare. Our study is a small cohort which is not representative of the whole population of the country. Multicentric studies involving larger cohorts are required for better understanding of the transmission dynamics and the potential role of asymptomatic and pauci-symptomic secondary cases in the spread of COVID-19. We used Ct values as an indirect measure of viral load. However, quantification of viral load could be best achieved by viral culture. Asymptomatic and pauci-symptomatic cases of COVID-19 remain potentially infectious during the first six days after a positive RT-PCR test. Considering that viral RNA shedding in these individuals decrease over time becoming undetectable in exhaled breath after Day 6, it would be prudent to consider release of such individuals from isolation after six days of a positive RT-PCR test. This would remove the unnecessary long periods of isolation, affecting individual well-being, society and access to healthcare. Further research is needed to understand the transmission dynamics of COVID-19 in asymptomatic and pauci-symptomatic cases, which will help in developing effective preventive strategies and thus, limit the spread of the disease. Comparative analysis of the average viral RNA shedding on masks for six consecutive days showed a gradual decline in the viral shedding, as evidenced by an increase in the median Ct values from Day 1 to Day 6 with a significant difference (χ 2 =55.78, p<0.001). 13 COVID-19): A Review of Clinical Features, Diagnosis, and Treatment A Systematic Review of Asymptomatic Infections with COVID-19 Presumed Asymptomatic Carrier Transmission of COVID-19 Asymptomatic cases in a family cluster with SARS-CoV-2 infection Temporal dynamics in viral RNA shedding and transmissibility of COVID-19 Viral dynamics in asymptomatic patients with COVID-19 8. orld ealth Organi ation ( O . Criteria for releasing COVID-19 patients from isolation. Scientific Brief. Geneva: WHO Screening of healthcare workers for SARS-CoV-2 highlights the role of asymptomatic carriage in COVID-19 transmission Detection of 2019 novel coronavirus (2019-nCoV) by real-time RT-PCR Transmission Potential of Asymptomatic and Paucisymptomatic Severe Acute Respiratory Syndrome Coronavirus 2 Infections: A 3-Family Cluster Study in China Contact Tracing Assessment of COVID-19 Transmission Dynamics in Taiwan and Risk at Different Exposure Periods Before and After Symptom Onset A Well Infant With Coronavirus Disease 2019 With High Viral Load Asymptomatic novel coronavirus pneumonia patient outside Wuhan: The value of CT images in the course of the disease Clinical characteristics of 24 asymptomatic infections with COVID-19 screened among close contacts in Nanjing Evidence of SARS-CoV-2 Infection in Returning Travelers from Wuhan, China Pathogenesis and transmission of SARS-CoV-2 in golden hamsters Estimating the Extent of True Asymptomatic COVID-19 and Its Potential for Community Transmission: Systematic Review and Meta-Analysis (pre-print) SARS-CoV-2 shedding and infectivity This study was funded by intramural project (Grant No. AIIMS/2020-21/3034). Written consent was obtained from every participant. The design of the study has been approved by the ethical committee of All India Institute of Medical Sciences, Jodhpur (Ref.no. AIIMS/IEC/2020-21/3034) and it conforms to standards currently applied in India. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.