1. NHS. Main symptoms of coronavirus (covid-19). www.nhs.uk/conditions/coronavirus-covid-19/symptoms/main-symptoms.
2. Covid-19: Runny nose, headache, and fatigue are commonest symptoms of omicron, early data show
3. Covid-19: GPs urge government to clear up confusion over symptoms
4. Yates K. (@Kit_Yates_Maths). Twitter. https://twitter.com/Kit_Yates_Maths/status/1510887393687072769.