SARS-CoV-2 Testing, How Frequent and How Specific?
An interesting article from a group in Harvard tried to gauge the importance of test sensitivity and frequency, looking at viral spread in a large group of people. They found that weekly surveillance testing, paired with case isolation, would limit an outbreak even if sensitivity of the test was not as good as PCR testing.
SARS-CoV-2 can spread from individuals with pre-symptomatic, symptomatic and asymptomatic infections. The re-opening of societies and the control of the virus spread will have to be facilitated with robust surveillance for which virus testing will be central.
After infection individuals undergo a period of incubation during which viral titres are usually too low to detect and this is then followed by an exponential growth of virus leading to a peak viral load and infectiousness and ending with declining viral levels and viral clearance.
The Harvard Group modelling results demonstrated that effective surveillance, including time to first detection and outbreak control, depended largely on the frequency of testing and the speed of reporting. It was only marginally improved by high test sensitivity.
They therefore concluded that surveillance should prioritise accessibility, frequency and sample to answer time and they suggested that weekly surveillance testing would limit an outbreak whereas every two weeks surveillance testing would allow the total number of infections to climb almost as high as if there was no testing at all.
To learn more about the services of The London General Practice please visit our home page.