Characteristics of viral specimens collected from asymptomatic and fatal cases of COVID-19

Abstract

We sought to determine the characteristics of viral specimens associated with fatal cases, asymptomatic cases and non-fatal symptomatic cases of COVID-19. This included the analysis of 1264 specimens found reactive for at least two SARS-CoV-2 specific loci from people screened for infection in Northern Nevada in March-May of 2020. Of these, 30 were specimens from fatal cases, while 23 were from positive, asymptomatic cases. We assessed the relative amounts of SARS-CoV-2 RNA from sample swabs by real-time PCR and use of the threshold crossing value (Ct). Moreover, we compared the amount of human RNase P found on the same swabs. A considerably higher viral load was found to be associated with swabs from cases involving fatality and the difference was found to be strongly statistically significant. Noting this difference, we sought to assess whether any genetic correlation could be found in association with virus from fatal cases using whole genome sequencing. While no common genetic elements were discerned, one branch of epidemiologically linked fatal cases did have two point mutations, which no other of 156 sequenced cases from northern Nevada had. The mutations caused amino acid changes in the 3′-5′ exonuclease protein, and the product of the gene, orf8 .

Epidemiological feature, viral shedding, and antibody seroconversion among asymptomatic SARS-CoV-2 carriers and symptomatic/presymptomatic COVID-19 patients

“…Innate immunity and cell-mediated immunity should play key roles in repressing viral replication in asymptomatic carriers [28]. Lower viral load and shorter viral shedding time should be due to a relative stronger antiviral immunity, as a high viral load often predisposes adverse outcomes of COVID-19 [9, 29]. To develop effective vaccine against SARS-CoV-2, it is important to arouse the specific cell immunity, instead of focusing on humoral immunity.…”

Comparison of SARS-CoV-2 viral load in saliva samples in symptomatic and asymptomatic cases

“…Gorzalski et al compared asymptomatic cases with all COVID-19 positive cases and demonstrated that the difference in mean Ct values was 2.08, which they determined as not statistically significant. All COVID-19 individuals had an average Ct value of 27.55 while asymptomatic cases had a Ct value of 29.63 (8). Consistent with the study of other matrices, our data using saliva as test matrix also demonstrated that the two populations have little difference between Ct values with a difference of only 1.75 Ct.…”

Epidemiological feature, viral shedding, and antibody seroconversion among asymptomatic SARS-CoV-2 carriers and symptomatic/ presymptomatic COVID-19 patients

“…Innate immunity and cell-mediated immunity should play key roles in repressing viral replication in asymptomatic carriers [27]. Lower viral load and shorter viral shedding time should be due to a relative stronger antiviral immunity, as a high viral load often predisposes adverse outcomes of COVID-19 [9,28].…”

“…It has been summarized from early studies that viral load of asymptomatic carriers is comparable to symptomatic patients [8]. In another study, it has been demonstrated that a considerably higher viral load is present in samples from fatal cases compared to asymptomatic carriers [9]. Difference in the dynamics of antibody against SARS-CoV-2 between asymptomatic carriers and COVID-19 patients remains unknown.…”