MedPageToday Peak on day 4 of symptoms, rather than day 1, has implications for rapid tests, experts say.
Viral load in COVID-19 infection peaks later now than in the early days of the pandemic, driving implications for rapid testing, researchers say.
A paper published in Clinical Infectious Diseases has been generating discussion among experts, who say high levels of population immunity are responsible for the shift.
That paper, by Nira Pollock, MD, PhD, of Boston Children’s Hospital, and colleagues, found that viral loads in the Omicron era peak about 4 days after the onset of symptoms, compared with a peak at symptom onset early in the pandemic.
“Early in the pandemic, before we had much in the way of immunity, it was observed that the viral load peaked either the first day of symptoms or even the day just before, so it was postulated that this is a lot of the reason why there was so much asymptomatic spread,” Paul Sax, MD, editor-in-chief of Clinical Infectious Diseases and director of the Infectious Disease Clinic at Brigham and Women’s Hospital in Boston, told MedPage Today.
“What’s happened more recently … is that the immune response kicks in much sooner,” Sax said. “So you start having symptoms as the virus is getting going, and then you have symptoms for even a few days before the viral load peaks.”
Pollock and colleagues wrote that the findings have “major implications for testing practice going forward.”