If you have underlying medical conditions or are at a higher risk, Professor Griffin says you should contact your GP or specialist as soon as you test positive to work out a plan (if you haven't already) and organise access to COVID-19 antiviral medication to prevent being hospitalised.
"Those antiviral therapies that we give to people as early as possible if they're high-risk, they work best if they are given early," he says.
But even if you're not considered high-risk, Professor Griffin says you should monitor for more severe symptoms developing.
"The main thing is breathing problems, so if you're feeling significantly short of breath and you've noticed a reduction in what you're able to do, it might be that you're having trouble walking upstairs or can't walk usual distances ... [that] would be a good indicator that it's a good time to get seen," he says.
"The main one certainly is shortness of breath, to the point where people need oxygen, that's when we really need to be able to help them.
"So if you're not able to do your normal things and feel quite short of breath, that's certainly a good reason to get seen straight away."
But Professor Griffin urges people to seek medical attention if they are extremely unwell, and not to be put off because of pressures on hospitals and GP clinics.
"It's important people know if they need medical attention, there are certainly avenues by which that can happen," he says.
"There are many options for telehealth, and many clinics where people can be seen with the right precautions."