A scratchy, sore throat, a relentless fever, a pounding head and a nasty cough – these symptoms all scream upper respiratory illness. But which one? Many of the viruses that cause upper respiratory infections such as influenza A or B and the virus that causes COVID-19 all employ similar tactics. They target the same areas in your body – primarily the upper and lower airways – and this shared battleground triggers a similar response from your immune system. Overlapping symptoms – fever, cough, fatigue, aches and pains – make it difficult to determine what may be the underlying cause. Now,…