Higher viral loads in asymptomatic COVID-19 patients might be the invisible part of the iceberg

Abstract

Purpose SARS-CoV-2 virus dynamics in different hosts and different samples and their relationship with disease severity have not been clearly revealed. The aim of this study is to evaluate the viral loads of 6 different sample types (nasopharyngeal/ oropharyngeal combined, oral cavity, saliva, rectal, urine, and blood) of patients with different ages and clinics, to reveal the relationship between disease course and SARS-CoV-2 viral load, and differences in viral loads of asymptomatic and symptomatic patients. Methods Nasopharyngeal/oropharyngeal, oral cavity, saliva, rectal, urine, and blood samples are collected from patients who were hospitalized with diagnosis of COVID-19 on admission. Laboratory analysis were carried out at Public Health Institute of Turkey Virology Reference and Research Laboratory. Results A total of 360 samples from 60 patients were obtained on admission. Fifteen (25%) of the patients were asymptomatic while 45 (75%) were symptomatic. A significant difference was found between mean ages of asymptomatic vs symptomatic patients (26.4 and 36.4, respectively, p = 0.0248). No PCR positivity were found in blood. Only one asymptomatic patient had positive PCR result for urine sample. Viral loads of asymptomatic patients were found to be significantly higher (p = 0.0141) when compared with symptomatic patients. Viral load had a significant negative trend with increasing age. A significant decrease in viral load was observed with increasing disease severity. Conclusion In conclusion, this study demonstrates that asymptomatic patients have higher SARSCoV-2 viral loads than symptomatic patients and unlike in the few study in the literature, a significant decrease in viral load of nasopharyngeal/ oropharyngeal samples was observed with increasing disease severity. Factors associated with poor prognosis are found to be significantly correlated with low viral load.

SARS-CoV-2 Quantitative Real Time PCR and Viral Loads Analysis Among Asymptomatic and Symptomatic Patients: an Observational Study on an Outbreak in Two Nursing Facilities in Campania Region (Southern Italy)

“…Elderly and female groups are con rmed to have higher frequencies of SARS-CoV-2 infection, thus age and gender could be considered important risk factors, as already described by other authors [5-18-27]. A non-negligible percentage of positive individuals (29.7%) showed an asymptomatic clinical course, moreover, median viral loads resulted to be statistically signi cant when compared to symptomatic ones, corroborating other authors' ndings [5]. These observations could suggest their possible role in viral circulation inside the nurseries.…”

“…In fact, elderly people are supposed to be particularly susceptible to the infection, especially in age class over 65 years [9-18-27]. The role of asymptomatic as a possible super spreader is unclear, in fact some authors has described various scenarios in which the viral load is higher in symptomatic elderly people [6-11-13, 17-27] instead of other cases where these ndings were observed in asymptomatic ones [5], that nds accordance with Ra et al which found that asymptomatic individuals showed persistent positive upper respiratory traits [19].…”

“…The disease clinical course is characterized by several factors, from asymptomatic to mild or severe viral respiratory tract infections, up to systemic in ammation and thrombosis [5]. Several other risk factors have also been identi ed to affect the disease course, such as gender, concomitant diseases, close contact and age [5,8].…”

“…The disease clinical course is characterized by several factors, from asymptomatic to mild or severe viral respiratory tract infections, up to systemic in ammation and thrombosis [5]. Several other risk factors have also been identi ed to affect the disease course, such as gender, concomitant diseases, close contact and age [5,8]. Indeed, Centers for Disease Control and Prevention (CDC) has identi ed 65 years old and older people at a greater risk of hospitalization and death for COVID-19, from 90x higher risk of death for 65-74 years old, up to 630x higher for over 85 years old people [9].…”

“…These ndings were supported by other studies reporting an association between high viral loads and more severe symptoms [6][7][8][9][10][11]17]. Otherwise, other studies did not show any statistically signi cant difference in viral loads between symptomatic and asymptomatic individuals [10][11][12][13][14][15][16][17][18]20], while Hasanoglu and colleagues showed that higher viral loads were found in asymptomatic patients when compared to symptomatic ones and that, the more the clinical course of the diseases was severe, the lower viral loads were observed, together with a signi cant negative trend with increasing age [5]. Thus, the clinical relevance of the role of viral loads is still unclear.…”