How long does infection last after infection with novel coronavirus? New study: Median 7 days
The New England Journal of Medicine recently published a new study from Joong University Hospital in South Korea.
In this study, novel coronavirus was cultured in respiratory samples from hospitalized patients with novel coronavirus. Although the patients remained positive for viral nucleic acid (PCR) for a long time after infection (median 34 days), the virus in vivo quickly lost its infectivity (median 7 days).
The infection duration of novel coronavirus was 12 days
The study, conducted by the South Korean researchers, included newly covid patients who tested positive for nucleic acid RT-PCR and were hospitalized in a hospital between February and June 2020.
All patients were isolated to nucleic acid negative for two consecutive times (at least 24 hours apart).
The study included 21 patients with a median age of 62 years, 76% of whom were male.
Of all patients included, 71% developed pneumonia and 38% received oxygen therapy.
According to the scientific scoring results, all patients included in this study had mild to moderate infection.
All patients received RT-PCR detection of covid nucleic acid at an interval of 1 to 5 days (median time: 2 days), and 165 samples were collected.
The researchers cultured 29 of 165 samples for the virus, the gold standard test for determining viral infectivity.
The virus culture of 29 samples showed that the median time from symptom onset (onset) to virus clearance in virus culture was 7 days.
The median time from onset of symptoms to nucleic acid RT-PCR for virus negative detection was 34 days (minimum 24 days).
The longest period of virus culture in all samples was 12 days.
The study also found that the Ct value of nucleic acid RT-PCR detection of virus culture positive samples was all below 28.4.
With the prolongation of the onset time and the increase of the CT cycle of RT-PCR, the positive rate of virus culture became lower and lower, and the infectivity of the residual virus in patients became lower.
Virus detoxification time does not equal to the infectious time of the virus
The duration of transmission of novel coronavirus and the level of infection associated with it have not been established.
At present, guidelines around the world to determine the isolation time of patients with covids are mostly based on the previous detoxification time of patients with covids.
A number of Chinese scholars have published detoxification studies on novel coronavirus in international authoritative medical journals.
The earliest study on the time of virus detoxification in patients with COVD-19 can be dated back to March 9 last year, when the Lancet published online a cohort study on the clinical course and risk factors of death in adult COVD-19 patients in Wuhan, led by Cao Bin, vice president of China-Japan Friendship Hospital.
The study, the first to describe new data for Novel Coronavirus detoxification, covered 191 patients (137 were discharged from hospital and 54 died).
The median duration of virus detoxification in surviving patients with covid was 20 days (range 8 to 37 days).
On June 19, 2020, Nature Medicine, a leading international medical journal, published “Clinical and immunological evaluation of asymptomatic patients with SARS-CoV-2”, a research team from Chongqing Medical University, China.
The study found that the median duration of detoxification in 37 patients with mild symptoms was 14 days, a relatively shorter period than in previous studies.
The detoxification time in the asymptomatic group increased significantly, reaching 19 days, compared with those with symptoms.
In the study, the researchers noted that the measured detoxification time was not the same as the time the virus became infectious, and further virus culture was needed for evaluation.
It is worth noting that although most patients with covid infection show a high degree of infectivity within about 7 days, there are some extreme cases, especially in people with low immunity.
Local time on November 4, 2020, “cell”, published online institutions such as the United States national institutes of health research institute of allergy and infectious diseases researchers completed a study reported a case of special covid cases: a woman with leukemia immune function is low infection will be coronavirus at least 105 days, at least 70 days detoxification has potential infectious, and always remain asymptomatic.