We report the dynamics of infectious SARS-CoV-2 viral shedding in adult and pediatric patients in mild, moderate, and severe clinical conditions. We assessed viral shedding and infectivity in the presence of anti-SARS-CoV-2 antibody response. This information is critical to creating algorithms for diagnosis, prevention, and control precautions during the hospital stay and after discharge.
In our study, the median duration of SARS-CoV-2 RNA shedding was 7 days in adults, and 5 days in children. The longest duration of viral RNA shedding was 19 days in a saliva sample of a child. In our study, the median duration from onset of symptoms to admission was three days. In other studies, the median viral RNA shedding time was reported as 17 days (15, 16). The prolonged shedding time was reported to be associated with high body temperature on admission, male sex, mechanical ventilation, delayed hospital admission, and hospital length of stay (15, 16). Being in parallel with these findings, we can explain our short viral RNA shedding time with the earlier hospital admission which provided effective and early case management with favipiravir and hydroxychloroquine, supportive treatment. The culture was positive in one clinically severe patient despite three days of favipiravir use.
In viral culture studies, the duration of infectious virus shedding was between 2-8 days after onset of the symptoms. Our study included mild, moderate, and severe cases. Our results were concordant with the findings that were limited with adult mild cases reported by Wölfel et al. that could not detect live virus after 8 days of the symptoms (3). Another study reported similar results without disease severity assessment (7).
In our study, RT-PCR positivity was obtained in all nasopharynx and/or saliva samples within five days of infection, and Ct values of nasopharyngeal and saliva RT-PCR tests increased after the first week of the disease. In recent reports, SARS-CoV-2 viral RNA was detected in saliva samples with higher viral loads than nasopharyngeal samples, and saliva was questioned for its role in the fast-spreading nature of the epidemic (8, 17, 18). We found viral shedding among 37.5% of the adult, and 38.4% pediatric saliva samples. In one patient (41 years old male), the virus was detected only in the saliva sample on admission, all other samples were negative. In our study, the latest saliva PCR positivity after the onset of symptoms was on day 10 in adults and day 19 in a pediatric patient with MAS. In another study, the viral RNA shedding in saliva was reported to be positive within 11 days (8). We did not find live virus in viral cultures of saliva samples. Saliva viral culture positivity was reported in previous studies (19). Based on these findings, we suggest that saliva could be a good diagnostic specimen, and the risk of virus transmission by saliva is lower than nasopharyngeal secretions.
In our patients, two adults with moderate and one child with mild clinical manifestations experienced diarrhea. None of these patient’s fecal samples were found to be positive for SARS-CoV-2 with RT-PCR. The prolonged shedding of viral RNA in feces raises concerns about the timing of discontinuing precautions during the hospital stay or after the discharge of the patients. These concerns are more important for children especially those who do not have toilet training or have poorer hand hygiene. In our study we detected viral RNA in feces of 3 adults at the 3, 7, and 14th days after onset of symptoms, and 10th day of the pediatric patient. In a study, the viral RNA was tested positive in feces of an adult patient 47 days after onset of the symptoms (20). Children show longer fecal shedding compared to adults, in some cases shedding over 70 days was reported (21-23). However, the presence of viral RNA in fecal specimens could not be considered as evidence of replicating live virus and do not confirm the potential for fecal-oral transmission. In our study, the viral culture of RT-PCR positive fecal specimens yielded no viral growth. Two studies reported the presence of the live virus in the stool samples (2, 24). To date, however, there have been no published reports of transmission of SARS-CoV-2 through feces. These results suggested that the risk of fecal-oral transmission is very low, and proper hand hygiene with no extra precautions for prevention of fecal transmission could be appropriate during the hospital stay or after discharge.
Although there is a low prevalence of SARS-CoV-2 in tears, exposure to tear may increase the risk for transmission to health care workers especially ophthalmologists. We found viral shedding in 3 out of 56 (5.3 %) tear samples in adults and one sample in children. We did not find an infectious virus in tear samples. Infectious virus was reported in an ocular swab specimen of a patient with conjunctivitis (10). The prevalence of shedding of the viral RNA in urine samples is very low (2, 6) and live virus in urine samples was detected in only one case report (9). We detected viral RNA in two urine samples of a patient with mild symptoms, however, live viruses did not exist in these samples. Based on our results, the risk of transmission through urine is very low.
The presence of viral RNA detection in serum of COVID-19 patients was reported; however, SARS-CoV-2 could not be cultured from serum (25). In accordance with the previous reports, we detected SARS-CoV-2 RNA 3 out of 54 (5.5 %) serum samples in 2 adults without the viral growth in cell culture and none of the serum samples were positive in children.
Serological diagnosis is very important especially for patients with low viral load and could not be diagnosed by RT-PCR tests. But, the timing of antibody tests is critical for an accurate diagnosis. In our study, the rates of total SARS-CoV-2 antibody were reached 88.8 % (8/9) in adults and 80% (4/5) in pediatric patients until the 14th day of symptom onset. Similar to our findings, Zhoa et al observed that total antibody positivity began to increase from the first week to 15 days of symptom onset (26). In another study conducted with 18 patients, positive antibody results were obtained at the end of the first week of disease (27). In our study, the delayed antibody response was observed in two patients with comorbidities (diabetes and juvenile idiopathic arthritis). Studies pointed out that delayed antibody response was associated with low viral load or impairment of adaptive immune response (28, 29). In our two patients (an adult and a pediatric case) viral RNA shedding lasted after seroconversion. The lack of infectious viruses in all samples after seroconversion suggested to us that a positive antibody test result could be used as a discharge criterion.
The strength of our study is having clinical cases, molecular, and viral culture studies in the same institute. Examining the patients in our institute shortened transportation time to the laboratory, all collected samples were processed and stored within one hour without a loss in infectivity. Therefore, we were able to isolate the live virus in samples with high Ct values. The number of samples per patient was 25 on average. Asymptomatic and critical patients were not studied. Fatal cases were not excluded. Viral dynamics at different sites should be further explored in larger populations of COVID-19 patients.
In conclusion, earlier hospital admission could be associated with shorter SARS-CoV-2 RNA shedding. Salivacoıuld be a good diagnostic specimen. The risk of fecal-oral transmission is very low, and strict hand hygiene measures could be preventive with no extra precautions. Positive antibody test result could be used as a discharge criterion, based on the lack of infectious virus in all samples after seroconversion.