Alliance for Pandemic Preparedness

May 12, 2021

SARS-CoV-2 Infectivity by Viral Load, S Gene Variants and Demographic Factors and the Utility of Lateral Flow Devices to Prevent Transmission

Category:

Topic:

Keywords (Tags): ,

  • SARS-CoV-2 index cases with lower PCR cycle threshold (Ct) values (suggesting a higher viral load) tended to have a higher proportion of contacts infected with SARS-CoV2, according to a study combining testing and contact tracing data from England between September 2020 and February 2021. Attack rates were 12% for index cases with Ct=15 and 5% for index cases with Ct=30. Attack rates were 55% higher among index cases with infections with S gene target failure (a known proxy for the B.1.1.7 variant). Attack rates were highest among household contacts (9%) followed by household visitors (7%), and lower among outdoor contacts (3%) and work/education contacts (5%). Contacts of children were the least likely to test positive, particularly following contact outdoors or at work/educational settings.

Lee et al. (May 11, 2021). SARS-CoV-2 Infectivity by Viral Load, S Gene Variants and Demographic Factors and the Utility of Lateral Flow Devices to Prevent Transmission. Clinical Infectious Diseases. https://doi.org/10.1093/cid/ciab421