Do you know the symptoms?
Parents are being urged to keep an eye out for the symptoms of croup after a spike in the number of reported cases of the virus.
Health officials in Wales have called on people to be wary of a "barking" cough as it one of the symptoms of croup.
The Cardiff and Vale University Health Board says its on the rise.
The virus causes the trachea to swell, making breathing difficult.
It usually affects children aged between six months and three years, with most cases occurring in two-year-olds, according to the HSE, though it can affect anyone up to fifteen years of age.
It is relatively rare but is as contagious as the common cold and so can spread easily.
Other symptoms of croup include a hoarse voice, difficulty breathing and a harsh grating sound when breathing in.
Most cases of the illness do not require treatment, though a doctor may prescribe corticosteroids to reduce the swelling in the airwaves.
Fewer than one per cent of croup cases end up in hospitalisation, the HSE says.
As it's so contagious, it can be difficult to prevent the spread of the virus but there are some measures you can take.
Regular hand-washing and avoiding sharing things like cups is key, while sneezing and coughing into a tissue rather than hands will also help to prevent the spread.
