Why the new crown spreads quickly: The patient has the highest load of saliva virus in the first week of the disease

On March 23, the University of Hong Kong and others reported in the academic journal The Lancet Infectious Diseasethat that the salivavirus load in patients with the new coronavirus pneumonia was highest in the first week after symptoms appeared and then declined over time. Unlike Severe Acute Respiratory Syndrome (SARS), patients with neo-coronary pneumonia have the highest initial viral load, which can explain the rapid spread of neo-coronary pneumonia.

(Original title: Willow Knife explains the rapid spread of the new crown: the highest load of saliva virus in the first week of the patient’s illness)

Journalist Zhang Wei

The authors note that one-third of patients with new coronary pneumonia can still detect viral RNA within 20 days or more of their saliva samples after swallowing (deep throat), even though antibodies to the surface and internal proteins of the neo-coronavirus have been formed. The viral peak load was positively correlated with age, and serum antibody levels were not related to clinical severity. Most patients develop an antibody reaction 10 or 10 days after the onset of symptoms.

The authors believe the findings underscore the importance of strict control over infection and early use of effective antiviral drugs in high-risk individuals. In addition, serological testing can be used as a supplement to RT-qPCR diagnosis.

Singapore researchers have made similar findings before. According to Singapore’s “Joint Morning Post” reported on March 2, Singapore researchers in the local new coronary pneumonia patients found that the initial symptoms of the patient is mild, but it is the body’s largest amount of virus, as the symptoms develop the virus gradually decreased, which means that the amount of the virus in the patient and the severity of symptoms is not positively correlated.

The latest study from the University of Hong Kong is entitled “Temporal profiles of viral load in posterior or opharyngeal saliva samples and serum antibody responses infection by SARS-CoV-2: an observational cohort study, carried out by the Li Ka-shing School of Medicine of the University of Hong Kong, the Department of Clinical Microbiology and Infection Control department of the University of Hong Kong, Shenzhen Hospital, etc., The responsible author is Dr. Kwok-Yung Yuen of the Department of Clinical Microbiology and Infection Control, Shenzhen Hospital, The University of Hong Kong.

Between January 22, 2020 and February 12, 2020, researchers screened 30 patients with new coronary pneumonia at two hospitals in Hong Kong, China, 23 of whom were included in the study. The median age of the patients was 62 years old and the age range was between 37 and 75 years old. 13 males and 10 women. Of these, 10 were seriously ill, all requiring supplementary oxygen and 13 cases of mild illness. Eleven out of 23 patients (48%) had chronic diseases, with the most common underlying diseases being 6 cases (26%) and 4 cases of diabetes (17%). Chronic underlying diseases are more common in patients with severe illness. Five patients were admitted to intensive care, three of whom required intubation. Two patients died.

Why the new crown spreads quickly: The patient has the highest load of saliva virus in the first week of the disease

Why the new crown spreads quickly: The patient has the highest load of saliva virus in the first week of the disease

Patient profile

The researchers found that the median viral load of saliva (deep throat) saliva or other respiratory specimens after swallowing (deep throat) was 5.2 log10 copies/mL. The salivary viral load is highest in the first week after the onset of symptoms and then decreases over time (slope -0.15, 95% confidence intervals of -0.19 to -0.11; R2 -0.71). The older the patient, the higher the viral load. One of the patients detected viral RNA 25 days after the onsgoing symptoms.

Why the new crown spreads quickly: The patient has the highest load of saliva virus in the first week of the disease

Continuous viral load time distribution for all patients. Most of the viral load data came from saliva samples after the mouth and phoraphher, and data from three intubation patients came from intra-trachea suction samples. S- saliva, E-breathing in the trachea.

Why the new crown spreads quickly: The patient has the highest load of saliva virus in the first week of the disease

Relationship between viral load and age or disease severity

In 16 patients who received serum samples 14 days or more after the onset of symptoms, the serum NP-IgG antibody positive rate was 94% (n-IgG 15), the NP-IgM antibody positive rate was 88% (n-14), and the RBD-IgG antibody positive rate was 100% (n-16), The positive rate of RBD-IgM antibody was 94% (n-15). THE LEVEL OF SARS-COV-2-NP OR SARS-COV-2-RBD IGG ANTIBODY LEVELS IS ASSOCIATED WITH NEUTRALISED TITER IN THE VIRUS (R2?GT; 0.9). Serum antibody levels were not related to clinical severity. In the experiment, a severe patient developed an early antibody reaction 6 days after the onset of symptoms. No genomic mutations were detected in the sequence sample.

In the discussion session of the paper, the author points out that the new coronavirus load is similar to the influenza virus load, and all reach a peak before and after the onset of symptoms. The viral load of SARS coronary and MERS coronavirus esthetized was reached about 10 days after the onset of symptoms and 2 weeks before the peak.

The authors believe that new coronavirus infection patients with high viral load when symptoms appear, suggesting that the virus is easy to spread, even if the patient’s symptoms are relatively mild. This finding could explain the effective human-to-human transmission that occurs in the community and health care environment.