March 25, 2020

Salivary viral load of SARS-CoV-2 after symptom onset, HFNO vs standard mask oxygenation for COVID-19 pneumonia, and time between resolution of symptoms and viral clearance

By Denise Baez

NEW YORK -- March 25, 2020 -- Today’s DG Alert covers salivary viral load of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) after symptom onset, high-flow nasal oxygenation (HFNO) versus standard mask oxygenation (SMO) during fibreoptic bronchoscopic intubation for coronavirus disease 2019 (COVID-19) pneumonia, and time kinetics of viral clearance and resolution of symptoms in COVID-19.

According to a study published in The Lancet Infectious Diseases, salivary viral load of SARS-CoV-2 was highest in patients during the first week after symptom onset and subsequently declined with time.

Kelvin Kai-Wang, MD, University of Hong Kong-Shenzhen Hospital, Shenzhen, China, and colleagues obtained samples of blood, urine, posterior oropharyngeal saliva, and rectal swabs from 23 patients with laboratory-confirmed COVID-19 from 2 hospitals in Hong Kong between January 22, 2020, and February 12, 2020. Serial viral load was ascertained by reverse transcriptase quantitative polymerase chain reaction (PCR). Antibody levels against SARS-CoV-2 internal nucleoprotein (NP) and surface spike protein receptor binding domain (RBD) were measured using enzyme immunoassay (EIA).

The median viral load in posterior oropharyngeal saliva or other respiratory specimens at presentation was 5.2 log10 copies per mL. Salivary viral load was highest during the first week after symptom onset and subsequently declined with time (slope, -0.15; R2 = 0.71). In 1 patient, viral RNA was detected 25 days after symptom onset. For 16 patients with serum samples available 14 days or longer after symptom onset, rates of seropositivity were 94% for anti-NP IgG (n = 15), 88% for anti-NP IgM (n = 14), 100% for anti-RBD IgG (n = 16), and 94% for anti-RBD IgM (n = 15). Anti-SARS-CoV-2-NP or anti-SARS-CoV-2-RBD IgG levels correlated with virus neutralisation titre (R2 >0.9).

“Posterior oropharyngeal saliva samples are a non-invasive specimen more acceptable to patients and healthcare workers,” the authors wrote. “Unlike SARS, patients with COVID-19 had the highest viral load near presentation, which could account for the fast-spreading nature of this epidemic. This finding emphasises the importance of stringent infection control and early use of potent antiviral agents, alone or in combination, for high-risk individuals.”

Another study published in the British Journal of Anaesthesia showed that among critically ill patients with COVID-19 pneumonia, HFNO provided a shorter intubation time and less frequent incidence of desaturation during attempts at fibreoptic tracheal intubation compared with pre-oxygenation by face-mask ventilation.

The study included 60 adults with confirmed COVID-19 pneumonia and hypoxaemia requiring intubation in the intensive care unit. Oxygen was administered for 4 minutes in the head-up supine position and then patients were instructed to take deep breaths before general anaesthesia. Fibreoptic tracheal intubation was attempted by 1 of 6 anaesthesiologists experienced in fibreoptic intubation. Each anaesthesiologist intubated sequences of 10 patients who were evenly divided into HFNO and SMO groups.

Intubation time -- the primary endpoint -- was shorter in the HFNO group versus the SMO group (68.5 seconds vs 76.0 seconds; P = .005). The lowest Spo2 during intubation was higher in the HFNO group than the SMO group (94.0% vs 91.2%; P = .001).

“HFNO shortened the duration of intubation,” wrote Cai-Neng Wu, MD, the First Affiliated Hospital of Guangzhou University of Traditional Chinese Medicine, Guangzhou, China, and colleagues. “The reasons for this are not clear, but one possibility is that interruption of attempts at tracheal intubation to carry out rescue face-mask ventilation was less frequently required in the HFNO group.”

Lastly, a study published in the American Journal of Respiratory Care and Critical Care Medicine showed that half of the patients with COVID-19 treated at a hospital in Beijing, China, were positive for SARS-CoV-2 even after resolution of symptoms.

De Chang, MD, Chinese PLA General Hospital, Beijing, China, and colleagues analysed data from 16 patients aged 3 to 68 years (68.8% male) with confirmed COVID-19 who were treated at PLA General Hospital between January 28, 2020, and February 9, 2020. All patients had throat swabs collected upon clinical presentation and every other day until the patient tested negative on real-time reverse transcriptase PCR on back-to-back days. Upon confirmation of the last negative test, the patient was asked to quarantine at home for 2 weeks with a follow-up visit to the hospital after 1 week to confirm the viral negative status.

Fever (87.5%) and dry cough (68.8%) were the most common symptoms and the mean duration of symptoms was 8 days (range, 6.25-11.5 days). Only 1 patient required respiratory support involving mechanical ventilation. Of the 16 patients, 8 (50%) remained viral positive even after the resolution of symptoms.

“This warrants us to investigate the ‘shedding window’ after the clinical recovery of the patient,” the authors wrote. “In this study, we report that half of the patients continued to be viral positive even after the resolution of symptoms up to 8 days, which may pose a significant challenge in controlling the spread of the disease. It is important to note that all our patients were milder infections that recovered from the disease. It is currently unclear if there is a delayed viral clearance in more vulnerable populations, such as those who are older or have immune deficiencies.”

SOURCE: American Journal of Respiratory Care and Critical Care Medicine, British Journal of Anaesthesia, and The Lancet Infectious Diseases
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