Is self-isolation for seven days enough to stop the spread of covid-19?

The UK government published their approach to exit lockdown on 11 May 2020. Self-isolation of infected individuals will remain a key part of the response to coronavirus, however the UK guidance to the general public is to self-isolate for 7 days from the onset of symptoms. After this individuals only need to continue to self-isolate if they still have a high temperature regardless of the continuation of other symptoms, with no recommended fever-free period at the end. This is at odds with guidance from other countries. 

The WHO recommends clinical recovery and two negative tests 24 hours apart before discharge from hospital, and to follow national guidance for self-isolation in non-hospitalised symptomatic cases. In earlier guidance, where testing is not possible, WHO recommended that confirmed patients remain isolated for an additional two weeks after resolution of symptoms. 

The European Centre for Disease Prevention and Control (ECDC) and the US Centers for Disease Control and Prevention (CDC) advise self-isolation for at least 8-14 days and 10 days respectively from symptom onset, and for at least three days after resolution of fever and clinical improvement of other symptoms. Although there is variation in the recommendation across countries, the UK’s is of a considerably shorter duration in comparison. This is additionally of concern due to reports of fluctuation in symptoms. The evidence behind the shorter duration of self-isolation has not been made public. The shorter duration means that individuals may come out of self-isolation while still potentially infectious. 

There is evidence that viral shedding can be prolonged, with the duration of viral shedding ranging from 8-37 days in a cohort of hospitalised patients in China. The median duration of viral shedding was 20 days in survivors and varied with disease severity. Another cohort of 56 patients with mild to moderate covid-19 reports viral shedding up to 42 days after onset of symptoms. Although viral shedding does not necessarily equate to infectiousness, we do not yet have clear evidence on how closely the presence of viral RNA relates to infectiousness, or indeed the average infectious period for those infected with covid-19, particularly in those with mild or asymptomatic disease. In the absence of clear evidence, it would seem foolhardy to dismiss the potential for ongoing infection risk, particularly in symptomatic individuals who are not repeatedly tested. 

Although testing capacity in the UK has been expanded, widespread community testing is not yet a reality, and the testing priority remains to inform clinical diagnosis. However, repeated testing (at least one negative test result with being symptom free after testing positive) could be used to determine when individuals can stop self-isolating, potentially releasing people from quarantine more quickly, allowing economic and social activity to resume as allowed post-lockdown.

Until this is systematically implemented, symptomatic individuals who are unconfirmed covid-19 or those who have tested positive once should be advised to continue to self-isolate for a certain period of time after complete symptom resolution. This would bring the UK guidance more in line with the WHO, ECDC and most other countries. 

Another issue with the UK’s self-isolation advice is the narrow spectrum of symptoms triggering the recommendation. Until yesterday, these have remained as only fever and/or new continuous cough. The UK government has just added loss of taste or smell to this list. However, there is now evidence for a wider range of symptoms associated with testing positive for covid-19 in the UK including fatigue, shortness of breath, chest pain, diarrhoea, abdominal pain and hoarse voice. ECDC has extended the range of symptoms to difficulty breathing, muscle pain and tiredness. CDC lists shortness of breath, muscle pain, chills, sore throat and new loss of taste or smell as symptoms, in addition to cough and fever. 

The UK is taking steps towards exiting the lockdown but the numbers of new infections per day remains considerable. Until covid-19 testing is implemented on a routine and repeated basis, self-isolation advice based on symptoms needs to be longer in its duration and wider in its indication. It is vital to get this right to ensure that we are able to supress disease circulation and avoid a second epidemic wave. A combined and systematic approach to case finding, contact tracing, isolation and support is fundamental to a successful management of the outbreak as the lockdown is eased. 

Nisreen A Alwan is an Associate Professor in Public Health at the University of Southampton and an Honorary Consultant of Public Health at University Hospital Southampton NHS Foundation Trust. @Dr2NisreenAlwan 

Nida Ziauddeen is a Senior Research Assistant in Public Health at the University of Southampton. @NidaZiauddeen

Grace Grove is an Academic Public Health Registrar and Clinical Research Fellow at the University of Southampton.