1
Aoki et al.
26
Cross-sectional
2021
Japan
24
N/A
Female/male
RT-PCR
There was a high correlation between viral load calculated using the RT-PCR cycle threshold value and antigen concentration. The tendency to decrease antigen concentration over time after disease onset is associated with viral load. Ct value: 25
N/A
N/A
N/A
N/A
N/A
SQT is fully compatible with RT-PCR and should be useful in diagnosing COVID-19 in any clinical setting
Nasopharyngeal swab
2
Aydin et al.
27
Case series
2021
Turkey
125
62,1
48.8% male
RT-PCR
The effect of SARS-CoV-2 viral load on saliva and other substances was not found in their prognosis. Ct value: 22.28
N/A
Hypertension, COPD, DM, malignancy, immune deficiency, cardiovascular disease, and asthma
N/A
N/A
N/A
The viral load of saliva in the early stages of COVID-19 infection may have a high prognostic value in predicting disease progression in patients over 45 years of age. Saliva is a good substance in COVID-19 screening
Oronasopharyngeal (ONP) samples and saliva samples
3
Berastegui-Cabrera et al.
28
Cross-sectional
2021
Spain
72
66
56% male
RT-PCR
No association was found between viral load in NP samples and the presence of SARS-CoV-2 RNAemia. The absence of differences in NP viral load between patients with SARS-CoV-2 RNAemia and without it proves that the clinical development index of COVID-19 patients is better than that of NP viral load. The median viral load in NP swabs = 6.98 log10 copies/ml (IQR, 5.15–8.20)
Arthromyalgias, coryza, cough, dyspnea, headache, odynophagia, diarrhea, anosmia, weakness, and dysgeusia
Chronic kidney disease, solid-organ transplantation, connective tissue disease, and chronic liver disease
Leukocytes: 5.22, 7.00, Neutrophils: 3.49, 4.79, Lymphocytes: 0.58, 1.36, Platelets: 158, 248, Hemoglobin: 13, 13.8, AST: 37, 26, ALT: 33, 23, Bilirubin: 0.59, 0.46, Sodium: 2, 4, Potassium: 2,1, Creatinine: 4, 6, C-reactive protein: 97.9, 44.9, Ferritin: 625.6, 442, D-dimers: 1430, 620, LDH: 450, 251.5,
ARDS, multiple organ failure, IMV, ICU admission, mortality
N/A
The presence of RNAemia SARS-CoV-2, in the first emergency assessment, is more common in patients with severe chronic underlying disease, such as chronic liver disease and solid organ transplantation, with viral load in the upper respiratory tract and with adverse outcomes
Nasopharyngeal swabs
4
Buetti et al.
29
Cross-sectional
2021
Switzerland
90
62.5
78.9% male
RT-PCR Nasopharyngeal swab
Viral load (log10 copies/ml), median [IQR]: 3.3 [1.8; 5.2] That viral load in the LRT was associated with the 6-week mortality
Cardiovascular, Immunosuppression, DM, Renal failure, Cancer, and Chronic respiratory failure
N/A
N/A
N/A
Delay in LRT virus averaged approximately 30 days in critically ill patients, and viral load in LRT was associated with 6-week mortality
5
Buder et al.
30
Cohort
2021
Germany
59
Median: 48 years
49%
Quantitative real-time PCR of respiratory samples
Median viral load (IQR): 6.80 × 104 (4.75 × 103–1.81 × 106) RNA copies/ml
N/A
10 patients had immunosuppression
N/A
34 outpatient, 20 admitted to ICU
Higher viral load correlated with a higher chance of viral transmission
SARS-CoV-2 infectivity correlated with viral load, with the best predictor of infectivity being viral loads above 1.0 × 107 RNA copies/ml. The probability of virus isolation from respiratory samples also correlated positively with viral load. Seroconversion terminated SARS-CoV-2 infectivity
6
Cho et al.
31
Pospective observational
2020
China
75
36.4 ± 16.3
48% male
RT-PCR Nasopharyngeal and deep throat swabs
There was no correlation between the recovery time of olfactory or gustatory disorders and the Ct value of PCR was sampled indirectly from nasopharyngeal swabs and deep throat reflected the viral load of SARS-CoV-2. Ct value: 28.3 ± 6.7
Rhinorrhea, Purulent nasal discharge, Taste change, Nasal blockage, Epistaxis, Cough, Fever, Dyspnea, and smell change.
N/A
N/A
N/A
N/A
There is no association between severity and improvement of olfactory and taste disorders with SARS-CoV-2 viral load
7
Chua et al.
32
Cross-sectional
2021
China
91
Asymptomatic Male:8.6 (4.3–11.0), Symptomatic Mean (IQR): 9.2 (4.0–15.0)
Asymptomatic 57.1% male, Symptomatic 44.4% male
RT-PCR Nasopharyngeal swab (NPS), and saliva samples collected on admission
The onset days of symptoms for all patients were inversely related to the NPS and saliva viral loads. Viral load (log10 copies/ml): lymphopenia (NPS, Saliva): 6.7, 5.8 viral load (log10 copies/ml):: nonlymphopenia (NPS, Saliva): 6.2, 4.9
N/A
Total white cell count (×109/L): 6, 5.8-Hemoglobin (g/dl): 12.8, 13.2-Platelets (×109/L): 258.4, 278.1-Urea (mmol/L): 3.4, 3.9-Creatinine (µmol/L): 41.6, 44.9-Creatine Kinase (U/L):122.5, 99.7-Troponin I (ng/l): 1.9, 11.3-C Reactive Protein (mg/dl): 1.4, 1.7-Erythrocyte Sedimentation Rate (mm/h):8.6, 12-
N/A
N/A
Salivary viral loads in hospitalized children with clinical and immune profiles are better than NPS
8
de la Calle et al.
33
Cross-sectional
2021
Spain
455
64.9 ± 18.1
56% male
rRT-PCR nasopharyngeal
Patients with respiratory failure had a higher viral load at admission than those who did not. Low viral load (Ct > 30), Intermediate viral load (Ct 25–30): 1.81, high viral load (Ct < 25): 2.99
Fever, Vomiting, Cough, Tachypnea, Diarrhea, SpO2 < 90% air room, Myalgia and Dyspnea
Cardiovascular disease, chronic renal disease, chronic lung disease, DM, immunosuppression, obesity, current or former smoker, and chronic liver disease
LDH (U/L): 326.6, GOT (U/L): 32, GPT (U/L): 25, CPK (U/L): 86, TnT (U/L): 10.5, C-reactive protein (mg/dl): 7.7, Ferritin (mg/dl): 699, D-dimers (ng/ml): 664
Need for supplemental oxygen, ARDS, noninvasive mechanical ventilation, ICU admission, Septic shock, Prone position, MACE event, Acute kidney injury (AKI), Venous thrombosis, Hepatitis, Respiratory failure, Invasive mechanical ventilation, and mortality
N/A
The SARS-CoV-2 viral load, measured by Ct value of rRT-PCR in pharyngeal swabs at admission, is a good indicator of the prognosis for respiratory failure
9
He et al.
34
Cohort
2020
China
23
41
43.5% males
qRT-PCR Pharyngeal swab
Minimum viral load: 40 Ct. Asymptomatic type patients had lower viral loads than common and severe types
Fever, cough, nasal congestion, dizziness, fatigue, arthralgia,
human endogenous retrovirus-H (Hervs) and Human picobirnavirus (HPBV)
Patients with severe disease had more abnormal laboratory test results (including leukopenia and lymphocytopenia)
no significant correlation was observed between age and Ct value also no association between Ct value and severity of illness was observed. Significant positive relation has been detected between peak viral load and severity of illness.
Weaker transmission capacity of asymptomatic cases due to the lower viral load
Asymptomatic type patients had lower viral loads than common and severe types
10
Jacot et al.
35
Cross-sectional
2020
Switzerland
N/A
0-99 years
Female/male
RT-PCR Nasopharyngeal swab
Range: 3–10 log copies/ml. Median: 6.78 log10 copies/ml In the first period of covid-19 outbreak viral load was higher SARS-CoV-2 viral load seem to be a substandard predictor of disease outcome, COVID-19 disease severity is not significantly related to viral replication in the upper and lower respiratory tracts
Fever cough
N/A
N/A
In the first period of covid-19 outbreak viral load was higher
below 1000 copies/ml values can be considered at slight risk of transmission
Despite there are significant differences between viral loads of different viruses, SARS-Cov-2 had a alike viral load to Respiratory syncytial virus and influenza B than other coronaviruses
11
Jain et al.
36
Comparative
2021
India
200
group A 35.23 ± 11.99, group B 35.32 ± 12.92
60% male
RT-PCR Nasopharyngeal swab
Group A with olfactory and taste dysfunction: 24.43 Ct. Group B without OTD: 27.39 Ct. The patients with taste and olfactoryimpairment at diagnosis had more viral load than patients without taste and olfactoryimpairment
Loss of smell and taste malaise sore throat cough fever nasal discharge
N/A
RT-PCR was utilized to test The COVID-19, with 3 gene detection: RdRp (RNA-dependent RNA polymerase), E (Envelope encoding) gene, and N (Nucleocapsid encoding) gene. For analysis cycle threshold was utilized.
N/A
N/A
The patients with OTD at diagnosis had more viral load than patients without OTD
12
Kam et al.
37
Cohort
2021
Singapore
17
7.7
Female/male
RT-PCR Nasopharyngeal swab
Symptomatic: 28.6 Ct. Asymptomatic: 36.7 Ct higher viral loads was seen in symptomatic children in comparison to asymptomatic children
Upper respiratory tract symptoms with mild sickness signs
N/A
N/A
patients with mild and severe chest CT involvement had significantly lower viral load in comparison to patients with no chest CT lesions.
symptomatic children in had high viral load in the first stage of sickness indicates the transmission potential of presymptomatic children.
Children with symptomshad higher viral loads than children without symptoms
13
Karahasan Yagci et al.
38
Cohort
2020
turkey
730
35
49.9% female
RT-qPCR Nasopharyngeal swab
Without CT scan involvement: 24.9 mild CT involvement: 27.8 moderate CT involvement: 29.4 severe CT involvement: 27.9. The oppositecorrelation of chest CT Total severity score (TSS) and viral load was seen. Significantly higher viral loads was observed in patients with no chest CT lesions in comparison to patients with mild and severe chest CT involvement
Fever, cough and dyspnea
Hypertension, diabetes mellitus, cardiovascular disease, chronic obstructive pulmonary diseases (COPD), cancers, HIV, collagenosis, and chronic liver disease
N/A
284 (39%) patients were admitted to hospital and 27 of patientsexpired during the hospitalization.
N/A
The oppositecorrelation of chest CT total severity score (TSS) and viral load
14
Kawasuji et al.
39
Case-control
2020
Japan
28
Median age: 45.5 years
53.6% male
rRT-PCR Nasopharyngeal swab
33.6 ± 5.5 Ct. A significant viral load and recovery time differencewas observed between patients with pulmonary involvement and patients without pulmonary involvement
N/A
N/A
N/A
Significantly higher viral load at the beginning of sampling in symptomatic patients than in asymptomatic patients was observed. Also, Children had significantly higher viral load than adults in the beginning of sampling.
A high nasopharyngeal viral load can be connected to the secondary transmission of COVID-19
Secondary transmission of COVID-19 can be related to high nasopharyngeal viral load. Additionally, the viral load can help describe why transmission is observed in some patients, but not in others, particularly among patients who live in same house
15
Kim et al.
40
Retrospective
2021
South Korea
106
Mean age: 28.0 ± 9.3 years
43.4% male
RT-PCR Nasopharyngeal/oropharyngeal swab
33.6 ± 5.5 Ct. Viral load and recovery time were significantly different between pulmonary involvement patients and patients without pulmonary involvement was observed
Cough, fever, headache, hyposmia, rhinorrhea, sputum, muscle pain, diarrhea, chest pain, ocular pain
Rhinitis, asthma, migraine, iron deficiency, anemia, hyperlipidemia, endometriosis, depression disorder, hair loss, atopic dermatitis
N/A
Recovery times were significantly slower in the patients with pulmonary involvement than patients without involvement.
N/A
Viral load and recovery time were significantly different between pulmonary involvement patients and patients without pulmonary involvement was observed. The cycle threshold cutoff value for the existence of pneumonia was 31.38
16
Kociolek et al.
41
Retrospective
2020
USA
817
0-17 years
52.1% male
RT-PCR Nasopharyngeal swab
Asymptomatic children: 2.0 × 103 copies/ml symptomatic children: 1.3 × 107 copies/ml. In children without symptoms lower viral load was found in their nasopharynx/oropharynx than children with symptoms
Cough, fever/chills, dyspnea, pharyngitis, loss of taste or smell, headache, abdominal pain, diarrhea, fatigue, myalgias, congestion/rhinorrhea, nausea/vomiting, rash, or conjunctivitis
Immunocompromised = 51. Diabetes = 19
N/A
Ct values were significantly higher in children without symptoms than children with symptoms. Also, significantly lower viral loads was observed in asymptomatic than symptomatic children.
N/A
Asymptomatic children had low viral loads in their nasopharynx/oropharynx than children with symptoms
17
Kriegova et al.
42
Prospective
2021
Czech Republic
1038
50.0 ± 3.3
Female/male
RT-PCR Nasopharyngeal swab
Asymptomatic and mild group 23.65 (±7.62) Ct. Moderate group 27.68 (±6.98) Ct. Severe and critical group 26.52 (±4.82) Ct. High levels of virus in the respiratory tract and excessive producing of chemokines and cytokines between first 2 weeks from the onset of symptoms were significantly related to severity of the COVID-19
N/A
N/A
N/A
self-conductnasal-swab in combination with direct RT-qPCRare easy, low-cost and quick CoV-2 testing method which could significantly increase the extent of the teststrategies which are needed to control the expansion of COV-19 during and post-pandemic era
N/A
High levels of virus in the respiratory tract and too much productionof chemokines and cytokines and between the first two weeks from the onset of symptoms were significantly related to severity of the COVID-19
18
Kwon et al.
43
Prospective
2020
South Korea
31
32-72 years
58% female
Nasopharyngeal swab RT-PCR
Initial viral load at five toten days from onset of symptoms in the asymptomatic and mild group, moderate group, and the severe and critical group was 32.65 (±7.62), 27.68 (±6.98), and 26.52 (±4.82) cycles
Fever, chill, cough, sputum, sore throat, dyspnea, rhinorrhea chest pain, headache, myalgia, nasal congestion, hyposmia, hypogeusia, pneumonia
Diabetes mellitus, hypertension, chronic lung disease, chronic liver disease, obesity (body mass index > 25), smoking
Old age, initial low WBC count, low platelet count, high CRP level, and fever were identified as factors associated with severity
Early increases in type I IFN response might be involved in the pathophysiology of severe COVID-19 by eliciting subsequent excessive responses of multiple cytokines and chemokines
N/A
Higher viral load, stronger antibody response, and excessive inflammation at first two weeks from onset of symptoms are related to the COVID-19 severity
19
Le Borgne et al.
44
Retrospective
2021
France
287
50.0 to 73.0, median age: 63.1
65.8% male
Pharyngeal swabs qRT-PCR
4.76 (3.29–6.06) log10 copies/reaction Nasopharyngeal viral load measured by RT-PCR during beginning emergency department (ED) viral load is not predictor of severity and mortality in COVID-19 patients
N/A
Hypertension, cardiovascular disease, diabetes mellitus, renal insufficiency, dialysis, COPD, malignancies, immunotherapy, corticosteroids
At emergency department admission, patients who didn't survive in comparison to survived patients. had significantly higher C-reactive protein (122 vs. 74 mg/L, p = .007) and creatinine (p = .036). Nonsurvivors were also more likely to present with anemia (p = .003) and lymphopenia (p = .02) than survivors
Forty-two patients (14.6%) died.
Nasopharyngeal viral load was measured by RT-PCR at emergency department admission viral load isn't predictor of severity and mortality in COVID-19 patients
20
Piubelli et al.
45
Cross-sectional
2021
Italy
273
N/A
Female/male
RT-PCR Nasal and Pharyngeal swabs
Viral load decreased during 2 months of quarantine (Ct decreased from 24 to 34). Alongside, the number of patients who need intensive care significantly decreased because of the reduction of viral load
N/A
N/A
More probable in high-transmission setting compared with low-transmission setting
ICU admission (5.3%)
N/A
N/A
21
Rauch et al.
46
Cohort
2021
USA
1808
27.3 ± 11
53% male
RT-qPCR and CRISPR-based assay Nasopharyngeal swab
Viral load = 286–510,000 copies/μl. The shift of viral load is shown in those who stayed at home
Nasal congestion, sore throat, fatigue, anosmia
N/A
8 positive participants by CRISPR-based assay and 9 by RT-qPCR were detected
All were alive at the end of the study
N/A
The prevalence of SARS-CoV-2 in cohort 2 was changed and it was because of decreased community restrictions and increased social interactions
22
Sarkar et al.
47
Cross-sectional
2020
India
138
N/A
Female/male
RT-PCR Nasopharynx swab (NPS) and oropharynx swab (OPS)
In those with Ct values between 17 and 23, patients had severe infections
N/A
N/A
N/A
N/A
In high viral load cases, the rate of transmission was 8-times more than low viral load cases. Patients with Ct above 33-34 were not contagious
In individuals with high viral load, the possibility of transmission was almost 8 times higher compared to low viral load individuals. Of those who were infected, 7% had a high viral load, 9% moderate viral load, and 84% low viral load based on Ct values. The probability of transmission in those with high viral load was 6.25 in comparison with law viral load with 0.8
23
Shlomai et al.
48
Cross-sectional descriptive
2020
Israel
170
62
58% Male
Nasopharyngeal samples RT-PCR
Viral load was significantly higherin ventilated and nonsurvivors patients (eightfold more than other patients). Low viral load was associated with decreased risk of mortality and intensive care
Hypoxemia
N/A
N/A
21 death
N/A
Viral load was directly linked to hypoxemia. Viral load was significantly related toblood oxygen saturation. The patient's age significantly correlated with viral load
24
Shrestha et al.
49
Cohort
2020
USA
230 health care personnel (HCP)
N/A
Male 36%
PCR Nasopharyngeal swab
Viral load in 2 or 3 days after onset of symptoms was the peak. Time since onset of symptoms was significantly related to viral load
N/A
Chronic lung disease, current smoker, chronic heart disease, hypertension, liver cirrhosis, immunocompromised, diabetes mellitus, chronic kidney disease
N/A
N/A
N/A
86.5% of transmission potential was in the first 5 days since onset of symptoms
25
Singanayagam et al.
50
Cross-sectional
2020
England
754 samples from 425 symptomatic cases
0-100 years old
Female/male
RT-PCR Nose, throat, combined nose-and-throat and nasopharyngeal swabs
There was no difference in Ct value between asymptomatic (Ct = 31.23), mild to moderate (Ct = 30.94), and severe cases (Ct = 32.55). In the first week of onset of symptoms, viral load was higher than the second week
N/A
N/A
In 42% of cases, culture was positive. The culture positivity during the first week of infection was significantly higher than the second week
N/A
N/A
Cases in the 81–100 year age group were more asymptomatic than other groups
26
Soria et al.
51
Cohort
2020
Spain
448
71.04 ± 18.29
45.7% male
RT-PCR Nasopharyngeal swabs
Mean Ct: mild (35.75 ± 0.45), moderate (32.69 ± 0.37), severe (29.58 ± 0.70). Viral load is a predictor of disease severity. High virus loading worsens the prognosis of the disease. Ct value was significantly law in the severe group in comparison with the moderate and mild group
N/A
Hypertension, cardiovascular disease, diabetes. Obesity, asthma, COPD
N/A
Cases of the severe group include 23% of total cases and all of them were admitted. Also, 18.3% died during 90 days after diagnosis, 75 cases in the severe group, three cases in moderate, and four in the mild group
N/A
N/A
27
To et al.
52
Cohort
2020
China
23
62
56.5% male
RT-qPCR Oropharyngeal saliva samples
The median viral load was 5 × 2 log10 copies/ml. The first week after the onset of symptoms, the viral load is high but decreases over time
Fever (96%), cough (22%), chills (17%), dyspnea (17%), runny and blocked nose, sore throat, chest discomfort, nausea, diarrhea, myalgia, malaise. In 15 (65%) CXR abnormalities were seen. In 17 (74%) multifocal ground-glass lung opacities were seen
48% had clinical medical illnesses including hypertension and diabetes
Those patients who had comorbidities had a lower anti-RBD IgG OD compared to those without comorbidities
Five patients were admitted to ICU, two of them required intubation, and also two of them died
N/A
Older age was associated with a higher viral load. The antibody response occurred 10 days or later since the onset of symptoms
28
To et al.
53
Cross-sectional
2020
China
12
62.5
58% male
RT-qPCR Nasopharyngeal or sputum specimen
The median viral load was 3.3 × 106 copies/ml. On the first day of hospitalization viral load was slightly higher than other days. After day 11 viral load started to shed till being undetectable
N/A
N/A
According to viral culture, saliva contains live viruses and potentially can transmit the virus
At the end of the survey, all patients were alive
N/A
Saliva can be obtained from the patient without invasive procedure and it leads to reduce in nosocomial transmission of the virus
29
Trunfio et al.
54
Retrospective cross-sectional
2021
Italy
200
56
58% male
RT-PCR Nasopharyngeal swab
Viral load was associated with the severity of the disease
Gastrointestinal, neurological, respiratory, and systemic involvement, headache, olfactory and gustatory dysfunction, nausea and vomiting, diarrhea, fever, arthralgia, asthenia and malaise, cough, dyspnea, pharyngitis, and runny nose
Participants of group A (Ct ≤ 20) had at least one comorbidity that was significantly different from the other two groups. Hypertension, COPD, asthma, obesity, active smoking, diabetes, cancer
N/A
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