Tutorial presented by Dr Owen Seddon, Consultant in Infectious Diseases and Microbiology
When considering a patient’s recovery, the COVID-19 throat swab should not be used to confirm a patient’s recovery because the test can remain positive for up to 120-days following initial infection. Determining whether a patient is non-infectious should not be guided by a COVID-19 throat swab.
Real world transmission of COVID-19, as seen via contact tracing, can be used to guide when a patient is ‘non-infectious’. Most onward transmission of COVID-19 happens just before or just after symptoms develop, during the first 48 hours. Infectiousness then diminishes over time, and after one week the risk of transmission is considerably reduced.
Viral culture is an alternative test to check for viable, infectious virus. In patients with mild infection, the presence of infectious virus has gone by day 10 of infection. For patients with moderate or severe COVID-19, the presence of infectious virus remains for up to 20 days.
To determine when a patient can be discharged from hospital, regardless of test status, the patient should be clinically recovered AND at least 20-days post infection.
Asymptomatic screening programmes are being used in the community for groups such as care home staff and healthcare teams. If someone has had COVID-19, they are likely to test positive for up to 90-days post infection and should therefore be excluded from these screening programmes.
Reinfection with COVID-19 is rare but may occur within 90-days of the original infection, and therefore it is important to differentiate between a patient who is recovering from COVID-19 and a patient who has been reinfected with COVID-19. The clinical assessment of the patient is important, a negative COVID throat swab will help rule out a reinfection, but a positive throat swab cannot not confirm reinfection. Use of more complicated sequencing tests might be necessary to compare the new infection with the original infection.