Box plots showing cycle threshold (Ct) values (IMAGE) Elsevier Caption A higher Ct value indicates a lower viral load in the samples with and without results by variants I, II, and IV assays using the extraction-free method. Some mutations were detected less frequently in samples with lower viral load. Credit Rafael R.G. Machado Usage Restrictions Please include attribution License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.