Immune systems are running low, what with the wintry weather and festive parties starting to kick in.

[Read more: What are the common symptoms of flu?]

As such, instances of croup have been increasing – but what is it? And who is affected?

What is croup?

Croup is when the voice box (larynx), windpipe (trachea) and airways to the lungs (the bronchi) are affected by a virus, usually the parainfluenza virus, and become swollen, inflamed and painful – it can lead to difficulty breathing. It’s a respiratory condition that can also be caused by the common cold virus and measles (if a child hasn’t been vaccinated). It tends to crop up most in autumn and winter, although you can contract it at any time. Croup generally lasts between a few days and a couple of weeks.

Who gets croup?

Croup is considered a childhood disease, and is most commonly found in children aged six months to three years, although one-year-olds are most prone to getting in. However, it can also affect babies below three months, and sometimes even teenagers – it is very rarely diagnosed in adults.

What are the symptoms of croup?

The NHS outlines the most common croup symptoms as:

1. Bark-like cough
2. Hoarse or croaky voice
3. Difficulty breathing
4. Harsh grating sound when breathing in (stridor)

With the following being common in the lead up to the condition: a sore throat, runny nose, cough and fever.

When should you go to hospital?

The NHS notes that if symptoms persist or become much worse, you should see a doctor, and in the following cases, go to hospital:

1. Severe breathing difficulties
2. An increased breathing rate (they're too breathless to feed or talk)
3. You're unable to hear sounds of breathing
4. A worsening cough or rasping sound (stridor)
5. Distress and agitation
6. Dark, blue-tinged or pale skin
7. The skin around their ribs and chest appears to be pulled in and tight, making the bones of their chest and ribs more visible
8. Abnormal drowsiness and sleepiness
9. Rapid heartbeat or a falling heart rate
10. Very high temperature
11. An inability to drink fluids

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How is croup treated?

Hydration is key, while children can also be treated by kids’ paracetamol. Cough medicine and decongestants are not advised, as they can increase drowsiness rather than help treat croup.

If you are concerned about a family member with croup, always contact your GP.