Few symptoms but high viral RNA load in upper respiratory airways is riskiest in COVID-19

March 29, 2020 0 By FM

Certain unique risk factors associated with novel coronavirus disease (COVID-19) leads to rapid spread of the virus and it necessarily makes the prevention of community transmission most difficult. A latest report in The Lancet Infectious Diseases stresses the implications for transmission from patients with few symptoms but high viral RNA load in the nasopharynx or upper part of the throat behind the nose, early in the course of disease. It also cautions that individuals within the community, policy makers, and frontline health-care providers, especially general and emergency room practitioners, should be alert and prepared to manage this risk.  The journal’s report,  https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30237-1/fulltext, though exploratory and not conclusive of any final observations, also says that the persistently high nasopharyngeal viral RNA load, and the detection of viral RNA in blood and pleural fluid, of the older patients with severe multi-organ dysfunction is also equally worrying.These findings have important implications for therapy and infection control. “Development and effective administration of antiviral therapy to critically ill patients throughout the course of disease is likely to remain important. Vigilance regarding the strict implementation of transmission precautions is required throughout the prolonged course of COVID-19 in patients who are critically ill, and ancillary staff responsible for collecting and disposing of bodily fluids or waste, who are at high risk during an outbreak, should be properly protected and trained,” the report says.The authors of the report describe the first cases of coronavirus disease 2019 (COVID-19) in Europe, which were reported in France. “The detailed clinical features of five patients with COVID-19 are aligned with the quantitative severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral RNA load from nasopharyngeal and other selected sampling sites. Previous studies in patients with SARS, Middle East respiratory syndrome (MERS), and COVID-19 generally provide insufficient detail to allow examination of the relationship between individual patient clinical course and viral RNA load,” states the report. The report observes that; “It is noteworthy that the presence of viral RNA in specimens does not always correlate with viral transmissibility. In a ferret model of H1N1 infection, the loss of viral culture positivity but not the absence of viral RNA coincided with the end of the infectious period. In fact, real-time reverse transcriptase PCR results remained positive 6–8 days after the loss of transmissibility.” For SARS coronavirus, viral RNA is detectable in the respiratory secretions and stools of some patients after onset of illness for more than 1 month, but live virus could not be detected by culture after week 3. The inability to differentiate between infective and non-infective (dead or antibody-neutralised) viruses remains a major limitation of nucleic acid detection. Despite this limitation, given the difficulties in culturing live virus from clinical specimens during a pandemic, using viral RNA load as a surrogate remains plausible for generating clinical hypotheses, the report said.