Coronavirus patients with mild symptoms have higher viral load and may have more virus shedding risk: Study
The amount of Covid-19 virus (viral load) collected from patients in the emergency department was found to be significantly higher in those with fewer or milder symptoms and who did not require hospitalization, the opposite of what might be expected, according to researchers from New York University (NYU) Langone Health. Such patients, who show mild symptoms, may carry a higher virus shedding risk potential, possibly representing an important overlooked population for infection containment, say investigators. According to the authors, their results support the concept that such patients may represent important sources of the virus.
“The results show that patients with mild Covid-19 symptoms may represent the most important ‘overlooked’ source of shedding given the higher viral load. Our findings suggest a higher shedding risk in less symptomatic patients, an important consideration for containment strategies in SARS-CoV-2 (the virus that causes Covid-19). Our study should increase awareness and should prompt the adherence to strict recommendation of social distancing and mask usage to avoid transmission,” recommends the team in their analysis published in The American Journal of Pathology. “In the hospital triage setting, the information from the viral load can be used to determine which patient would receive a negative pressure room. In the outpatient setting, clinicians can utilize viral load as a quantitative metric to reinforce the importance of self-isolation and face coverings to reduce the risk of spreading the infection,” they suggest.
The authors also found that a patient's history of cancer and cardiovascular disease is associated with higher viral loads even after adjusting for age. “Furthermore, we identify a novel association between viral load and a history of cancer. Larger studies are warranted to validate our findings,” they write.
The study was designed to determine possible associations between the viral load measured in patients positive for SARS-CoV-2 and their clinical parameters including the severity of symptoms, hospital admission vs direct discharge, length of hospitalization, admission to the intensive care unit, length of need for oxygen support, and overall survival.
“It appears that the viral load peaks in the early stages of the disease. Although it is not associated with the duration of symptoms, their severity or outcome, it appears that the viral load is an important epidemiological surrogate marker of infectivity in mildly symptomatic and asymptomatic non-hospitalized patients,” says co-lead investigator Dr Paolo Cotzia, assistant professor, Department of Pathology, and assistant director, Center for Biospecimen Research and Development, NYU Langone Health, New York City. “Whether the viral load in these patients stays the same or changes in later stages of the disease remains to be investigated and could provide further insights on the dynamics of viral replication,” adds Cotzia.
The research team included 205 patients who visited the emergency department at a New York City tertiary care center with confirmed Covid-19. The analysis shows that 165 patients were discharged from the emergency department, and 40 patients were hospitalized. Non-hospitalized patients were younger overall, and other characteristics were similar across the group. The median duration from symptom onset to sample collection for the hospitalized group was five days compared with three days for the discharged patients.
According to the researchers, the initial viral load was significantly lower in patients who required hospitalization compared to those who were discharged. The association remained significant even after adjustment for age, sex, race, body mass index, and other existing medical conditions. They also found that a higher viral load was associated with a shorter duration of symptoms in all patients and was not associated with disease severity.
“We showed that viral loads are inversely correlated with disease severity. We believe that higher viral loads are seen in mild disease rather than a severe disease as they reflect the time from onset of infection. These findings are interesting when interpreted within our current knowledge of the natural history of Covid-19. While many Covid-19 patients recover from their initial symptoms over 14-21 days, a sizeable proportion of patients show clinical deterioration to severe disease which usually occurs a week after symptom onset,” says the research team. They explain, “In our cohort, viral loads detected from nasopharyngeal sampling in patients requiring hospitalization (most of which had severe or critical symptoms) were obtained at a later time point in the disease course. This fact is on par with prior studies demonstrating that longer disease duration is not necessarily associated with a higher viral load but rather a lower viral load.”