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)

Abstract

Background In December 2019 an outbreak of Severe Acute Respiratory Syndrome Coronavirus 2 was first observed in Wuhan, China. The virus has spread rapidly throughout the world creating a pandemic scenario. Several risk factors have been identified, such as age, sex, concomitant diseases as well as viral load. A key point is the role of asymptomatic people in spreading SARS-CoV-2. An observational study in Southern Italy was conducted in order to elucidate the possible role of asymptomatic individuals related to their viral loads in the transmission of the virus within two nursing facilities. Methods Oro-nasopharyngeal swabs from 179 nursing health care workers and patients were collected. SARS-CoV-2 RT-qPCR was performed and viral loads were calculated by using standard curve. A statistical correlation between viral loads, the presence/absence of symptoms, age and sex variables was investigated. Results SARS-CoV-2 was confirmed in the 50.8 % (n = 91) of the cases. Median age of positive individuals resulted higher than negative ones. Over 65 year as well as female individuals showed higher susceptibility to SARS-CoV-2 infection, OR = 3.93 and 2.86, respectively. Among 91 tested positive, the 70.3 % was symptomatic while the 29.7 % was asymptomatic. Median viral loads of asymptomatic individuals were found statistically significant higher than symptomatic ones (p = 0.001), while no influence was observed in age and sex variables. The presence of comorbidities was 8.9 folds higher in patients who showed and developed symptoms compared to non-symptomatic ones. Moreover, higher viral loads were found in patients who remained asymptomatic than pre-symptomatic (p = 0.022). Conclusions A range from 9.2 to 69 % of confirmed SARS-CoV-2 cases remains asymptomatic, moreover, sporadic transmissions from asymptomatic people are reported, that makes their involvement an important issue to take into account in the spreading control of the virus. An asymptomatic clinical course was observed in the 29.7 % of positive individuals, moreover, median viral loads resulted to be statistically significant when compared to symptomatic ones. Surely, such a relevant frequency should not be ignored in relation to the spread of the disease in an environment which has not only important intrinsic (age, sex, concomitant diseases) but also extrinsic factors such as high population density and close contacts.

At-home sample collection is an effective strategy for diagnosis and management of symptomatic and asymptomatic SARS-CoV-2 carriers

“…We found that the mean and median Ct values were significantly lower among symptomatic than asymptomatic cases, indicating that, on average, viral loads are higher in those with symptoms. This finding contrasts with previous studies demonstrating either no difference in the mean Ct value by symptom status, or lower average Ct values from asymptomatic cases; however, their sample sizes were much smaller (n = 48 to 213 infections) and represent single regional sites [ 37 – 39 ]. Conversely, we captured Ct values for 7571 positive tests (including repeat tests for the same infection) across a large geographic region (i.e., United States).…”

Occurrence and transmission potential of asymptomatic and presymptomatic SARS-CoV-2 infections: Update of a living systematic review and meta-analysis

“…Only 22 of 130 studies reported the median or mean age [ 38 , 47 , 70 , 76 , 77 , 83 , 85 , 95 , 99 , 119 – 121 , 124 , 126 , 128 , 133 , 134 , 139 , 143 , 146 , 152 , 164 ] and only 5 studies included children only [ 65 , 67 , 110 , 115 , 118 ]. Only 31 studies reported the sex of people with asymptomatic SARS-CoV-2 ( Table 1 and S2 Table ) [ 38 , 47 , 51 , 53 , 70 , 71 , 75 , 76 , 83 , 85 , 95 , 99 , 107 , 119 – 122 , 124 , 126 , 128 , 133 , 134 , 139 , 143 , 146 , 147 , 150 , …”

Occurrence and transmission potential of asymptomatic and presymptomatic SARS-CoV-2 infections: update of a living systematic review and meta-analysis

“…Amongst all 130 included studies, 88 studies used more than one method of follow-up to ascertain asymptomatic status (Table 1, S2 Table). Only 22 of 130 studies reported the median or mean age [38,47,70,76,77,83,85,95,99,119-121,124,126,128,133,134,139,143,146,152,164] and only five studies included children only [65,67,110,115,118]. Only 31 studies reported the sex of people with asymptomatic SARS-CoV-2 (Table 1, S2 Table) [38,47,51,53,70,71,75,76,83,85,95,99,107,119-122,124,126,128,133,134,139,143,146,147,150,153,158,162,164].…”

“…Only 22 of 130 studies reported the median or mean age [38,47,70,76,77,83,85,95,99,119-121,124,126,128,133,134,139,143,146,152,164] and only five studies included children only [65,67,110,115,118]. Only 31 studies reported the sex of people with asymptomatic SARS-CoV-2 (Table 1, S2 Table) [38,47,51,53,70,71,75,76,83,85,95,99,107,119-122,124,126,128,133,134,139,143,146,147,150,153,158,162,164]. The types of included studies changed across the five versions of the review.…”