For some people with COVID-19, the pain in their skull is so intense they consider a trip to the emergency room.
For others, it might come in throbbing waves or feel like a constant mild ache; it could be gone within minutes of taking painkillers or still be there months later.
Air Canada (AC.TO) flew more than 100,000 passengers in one day for the first time since the COVID-19 pandemic hit, another sign that the airline's recovery is underway as travel demand returns.
The official list of Covid-19 symptoms has been expanded to include nine new signs of illness.
The extension of the symptoms list to include ailments such as sore throat, fatigue and headache could help to reduce infections, one expert said.