Croup cough is highly contagious. As mentioned, this viral infection can spread both via airborne droplets, and via surfaces. If you should breathe in the droplets, or if you should touch a surface that has been infected with croup and then touch your face, eyes or nose, then this can cause the condition to spread quickly.
Coup is most contagious during the first few days of the condition, which may be before the main symptom (cough emerges).
While this isn’t a symptom as such, it can sometimes help to more quickly diagnose the problem: if you notice that your child is suffering from croup and they have been spending time with other people that now have the cough, then this could provide a hint as to what might be the cause.
In order to limit the spread of croup, it is important to ensure that you wash your hands thoroughly, that you wipe down surfaces after use, and that you are careful to limit the spread of spittle by putting your hand in front of your couch. Generally, it is good advice to try and avoid touching your hands to your face and mouth wherever possible.