Currently, nucleic acid testing (RT-PCR) of patients is the “gold standard” for the diagnosis of NCCP. However, the dynamics of the virus in patients with NCCP are still not fully determined.
A team of researchers from the Beijing CDC and the University of Hong Kong published a corresponding article in The Lancet Infectious Disease, a top medical journal, on February 24 local time, reporting on the viral load of different types of clinical samples collected from 82 patients diagnosed at different stages of infection, in an attempt to answer this question.
The study showed that viral load peaked early (5-6 days after the onset of symptoms) in patients with neoconiosis, unlike the time of peak in SARS (which had to be on day 10 of the onset of symptoms). Sputum viral load is higher than pharyngeal swabs in patients with neocolonitis. Also, the patient may have been infectious before the onset of symptoms. The study also found a high sputum viral load at the time of death in a patient with a new crown.
Corresponding authors of the study are Leo L M Poon, a professor at the School of Public Health at the University of Hong Kong, and Quan-Yi Wang of the Beijing CDC. Leo L M Poon is an expert in emerging viruses and has been involved in the biology of ribonucleic acid viruses and molecular diagnostic approaches to infectious diseases, with a focus on influenza viruses and coronaviruses, and was one of the first to identify atypical pneumonia caused by a novel coronavirus and to decipher the sequence of the first atypical pneumonia coronavirus during the SARS outbreak in 2003.
Samples, including pharyngeal swabs, sputum, urine, and stool, were collected consecutively every day after admission for two patients in Beijing, from days 3-12 after onset for patient 1 and days 4-15 for patient 2. These samples were confirmed by N gene-specific quantitative RT-PCR assays.
Viral load in pharyngeal swabs and sputum samples peaked around days 5-6 post-onset and ranged from 104-107 copies/mL (Figure A, B). This change in viral load pattern is clearly different from that of SARS patients, who generally reach peak viral load around 10 days after the onset of illness. In contrast, the viral load of sputum samples was generally higher than that of pharyngeal swab samples.
Neocoronavirus RNA was not detected in urine or stool samples from either of these patients.
Viral load dynamics in patients with neocoronavirus infection. mean viral load of consecutive pharyngeal swab and sputum samples in patient #1 (A), mean viral load of consecutive pharyngeal swab and sputum samples in patient #2 (B), viral load of pharyngeal swab and sputum samples at different stages of infection in 80 patients (C), correlation study between viral load of pharyngeal swab samples and viral load of sputum samples (D)
The team also studied respiratory samples from another 80 patients at different stages of infection, including nasal swabs (1), pharyngeal swabs (67) and sputum samples (42). The range of viral load was 641-1.34×10^11 copies/mL, with a mean viral load of 7.99×10^4 copies/mL for pharyngeal swabs and 7.52×10^5 copies/mL for sputum (Figure C), and the only nasal swab (day 3 post-onset) showed a viral load of 1.69×10^5 copies/mL.
Overall, viral load was high (>1×106 copies/mL) early after onset, the authors said.
The investigators found that samples taken from a patient who died on day 8 after onset showed a very high viral load (1.34×1011 copies/mL) in sputum samples at that time.
Notably, two individuals who were under close surveillance due to exposure to patients with neo-crown tested positive for RT-PCR the day before the onset of illness, indicating that the infected individuals were infectious prior to the onset of symptoms.
In addition, stool samples from nine of the 17 cases of new coronavirus infection (days 0-13 of onset) showed positive RT-PCR. The authors cautioned that although the fecal viral load was lower than that of respiratory samples, at 550-1.21 × 105 copies/mL copies, precautions should still be considered when handling fecal samples.
Content source: Punch News