Dr Phil Kieran: My teenager is finding it difficult to shake off her bug

Most of the time, when we pick up a bug, it will take somewhere between one and two weeks to settle down. The cough and congestion can go on for another week or so. All told, it's pretty normal to feel unwell for about three weeks.

It sounds like you and your family had a viral upper respiratory infection, and thankfully, most of you recovered quickly. In your daughter’s case, she is still suffering from the effects of this infection. If it's more than three weeks since she first got sick, it would be worth bringing her to her GP for a checkup.

Fatigue can have many different causes, and figuring out what is going on can be challenging. We would need to rule out an ongoing infection, as she may have picked up a different infection on top of the virus you all had. 

A secondary infection happens occasionally if our airways are inflamed due to a viral infection. Often, doctors can figure this out by carefully noting the symptoms and examining the patient.

Your daughter may need some blood tests to check for other unrelated causes for her tiredness. Fatigue may indicate thyroid problems or iron, vitamin B12, or folic acid deficiencies. 

I see young women with low iron levels causing fatigue relatively frequently. Many have started having periods and aren’t always getting enough iron in their diet.

I would also wonder if she is not getting enough sleep due to the symptoms you describe. Her sinuses may be full of mucus, leading to significant nasal congestion, which can make breathing difficult and lead to snoring while asleep.

If she breathes through her mouth during the night, she may find relief from a saline sinus rinse. This is a saltwater rinse sprayed into the sinuses to clear the airways. She should do this about an hour before bedtime.

Post-viral fatigue is a term for tiredness experienced by some people after infections, and often, the diagnosis if all the other tests prove normal. If this is the case for your daughter, it's critical she continues to engage in normal behaviour as much as possible. She may need to look into managing her energy levels as over-exertion can cause a significant crash in energy levels the day after, known as post-exertional malaise. Post-viral fatigue often resolves within three months without further intervention, but some cases can drag on for longer.

• If you have a question for Dr Phil Kieran, please send it to parenting@examiner.ie