(HealthDay News) — Twenty percent of COVID-19 cases shed infectious virus before symptom onset, according to a study published online Aug. 18 in The Lancet Respiratory Medicine.
Seran Hakki, PhD, from Imperial College London, and colleagues conducted a prospective, longitudinal, community cohort of contacts of newly diagnosed confirmed severe acute respiratory syndrome coronavirus 2 index cases. Infectiousness among household- and non-household-exposed contacts aged 5 years or older was characterized across the full course of infection. Data were included for 57 people who were at the start of infection; the onset and end of infectious viral shedding were captured for 42 cases.
The researchers found that the median duration of infectiousness was five days. Sixty-three percent of 38 cases had detectable virus before symptom onset, but only seven of 35 cases shed infectious virus presymptomatically. Onset of symptoms was a median of three days before peak viral RNA and peak infectious viral load. Sixty-five and 24% of 34 cases continued to shed infectious virus five and seven days after symptom onset, respectively (survival probabilities, 67 and 35%, respectively). Poor correlation was seen for lateral flow device results with infectious viral shedding during the viral growth phase, but correlation was high during the decline phase (sensitivity, 67 and 92%, respectively).
“Preliminary evidence from our study has already informed policy and the real-world evidence presented here could be used to improve infection control policies and optimize guidance on self-isolation to minimize secondary transmission,” the authors write.
One author disclosed financial ties to Janssen and Takeda.
