COVID-19 detoxification research： the time in feces is longer than that in breathing, and the detoxification of men is slower than that of women
A new study on the time and load of virus in different tissue samples of patients with novel coronavirus (SARS-CoV-2) by medical college of Zhejiang University shows that the duration of virus in feces is much longer than that in respiratory tract and serum samples, and the peak of virus load in feces appears later.
On April 21st, local time, the top international medical journal BMJ (British Medical Journal) published the research article "Viral load dynamics and disease severity in patients infected with SARS-CoV-2 in Zhejiang Province, China, January-March 2020: Retrospective Cohort Study ",the research team includes many medical research teams in Zhejiang, including the Clinical Laboratory Center of the First Affiliated Hospital of Zhejiang University School of Medicine, the Cooperative Innovation Center for Diagnosis and Treatment of Infectious Diseases, the Bone Marrow Transplantation Center, Pharmacy Department, Respiratory Diseases Department and other departments; Institute of Laboratory Medicine; Zhejiang University; Zhejiang pancreatic disease research and innovation center, etc.
The correspondent of this article is Liang Tingbo, a professor at the Faculty of Medicine of Zhejiang University and a winner of the National Natural Science Foundation’s Outstanding Youth Fund.
At present, the relationship between the changes of viral load and the severity of diseases in different tissues such as lower respiratory tract, feces, serum and urine in Covid-19 is still unknown, and this information is very important for the formulation of disease control strategies and clinical treatment.
Through retrospective cohort study, the authors systematically evaluated the viral load of 3497 samples collected from 96 inpatients infected with SARS-CoV-2 in the First Affiliated Hospital of Zhejiang University Medical College from January 19 to March 20, 2020, and analyzed the temporal variation of viral load and the correlation between viral load in different sample types and disease severity.
The research team found that,The duration of SARS-CoV-2 in fecal samples was significantly longer than that in respiratory tract and serum samples.This highlights the risk of fecal transmission of virus, indicating that it is necessary to strengthen the management of fecal samples in the prevention and control of COVID-19 epidemic.
In addition, it is worth noting that in critically ill patients, the virus persists in the respiratory system and feces for a longer time and with a larger load, and the peak time may be later than known.
The duration of virus in feces is long, and the viral load in respiratory tract samples is the highest.
The sample of the study included 22 mild patients and 74 severe patients. The research team collected their epidemiological, clinical and laboratory characteristics, treatment and outcome data through the patients’ electronic medical records.
The results showed that Covid-19 RNA was detected in feces of 55 patients (59%) and serum of 39 patients (41%), and there was no difference in the detection rate of fecal virus between mild patients and severe patients.
It is worth noting that the detection rate of SARS-CoV-2 in respiratory tract samples of confirmed patients gradually decreased from 95% in the first week to 54% in the fourth week, and subsequent respiratory tract samples were negative. However, the positive rate of stool and serum samples gradually increased from the first week, and then began to decrease from the third week.
Although the detection rate of viral RNA was as high as 50% in the urine of SARS patients, in this study, researchers only found Covid-19 RNA in the urine of one critically ill patient.
The detection rate of virus RNA in serum is also obviously different from that of SARS. Some previous studies found that as many as 79% of serum samples contained SARS virus RNA in the first week of symptoms, and the proportion was about 50% in the second week. However, in this study, the detection rate of SARS-CoV-2 in patients’ serum was only 41%.
The number of virus-positive patients in respiratory tract, feces, serum and urine samples of patients diagnosed with mild or severe COVID-19 at different stages after the onset of symptoms. The figures in the figure are the number of COVID-19-positive patients in a certain organization/the total number of patients tested.
The researchers found that confirmed patientsThe duration of virus in feces (22 days, quartile range 17-31 days) was significantly longer than that in respiratory system (18 days, 13-29 days) and serum samples (16 days, 11-21 days)..
In addition, the duration of virus in respiratory tract samples of patients with severe diseases is significantly longer than that of patients with mild diseases; However, there was no significant difference in viral load in stool and serum samples between mild patients and severe patients.
Different kinds of tissue samples and different viral loads
There are significant differences in viral load in different tissues. Among the research samples, respiratory tract samples have the highest viral load, followed by fecal samples, and serum samples have the lowest viral load.
Through local weighted regression analysis, the researchers found that in the mild group, the viral load in patients’ respiratory tract samples reached its peak from the second week of disease onset; In the severe group, the viral load in the respiratory tract samples of patients continued to increase in the third and fourth weeks.
Similar to the change trend of viral load in respiratory tract samples of severe patients, the viral load in stool samples of patients was the highest in the third and fourth weeks after the onset of the disease.
Changes of viral load in respiratory tract samples of mild and severe patients and all stool samples since symptoms appeared. Purple represents respiratory tract samples of severe patients, yellow represents respiratory tract samples of mild patients and pink represents stool samples of all patients.
The duration of virus in lower respiratory tract samples was longer than that in upper respiratory tract, and the peak appeared later.
The researchers found that the researchers found that,The type and duration of antiviral treatment have no overall effect on the duration and viral load of the virus..
In critically ill patients, the virus duration of patients who received glucocorticoid treatment for more than 10 days was much longer than that of patients who received glucocorticoid treatment for less than 10 days, and other different treatment methods had no effect on the virus load.
At present, the therapeutic effect of glucocorticoid and antiviral drugs on SARS-CoV-2 patients is still unclear. The researchers stressed that it is impossible to evaluate the effects of antiviral drugs and glucocorticoids at present because the types and doses of antiviral drugs and glucocorticoids have not been analyzed.
The authors said that in the next step, the effectiveness of antiviral drugs and glucocorticoids needs to be verified by more multicenter randomized studies.
After stratified analysis of critically ill patients, the researchers found that,The duration of the virus in men is significantly longer than that in women, and the duration of the virus in patients over 60 years old and male patients is longer..
The reasons for the gender difference in virus duration are not only the differences in immune status between men and women, but also the differences in hormone levels. The reason why the virus lasts longer in the elderly patients is partly due to immune aging, and another reason is that the content of Covid-19 "receptor" angiotensin converting enzyme 2 in the alveoli of the elderly is higher.
Previous studies have found that the peak load of SARS-CoV-2 in patients’ upper respiratory tract samples appears in the early stage of the disease. However, the researchers found that in the lower respiratory tract samples, Covid-19’s "viral shedding" lasted longer, and the peak appeared later, and the peak amount of detoxification did not appear until about two weeks after the onset of symptoms.
The researchers believe that these findings are very important for effectively controlling and preventing the COVID-19 epidemic, because it shows that the whole disease process of SARS-CoV-2 patients must be strictly managed.
Based on the research results, the authors believe that the role of fecal excretion in the spread of SARS-CoV-2 can not be ignored. However, in the prevention and control of SARS-CoV-2 epidemic, the feasibility of large-scale detection of fecal samples also needs comprehensive and careful evaluation.