Croup causes a bad barking cough, trouble breathing, and sometimes strider which is a wheezing noise. You don't get croup unless you have another disease, but those diseases are passed through the air when a person coughs.
Croup can be treated by steaming up the bathroom and sitting to breathe the hot air for 20 minutes. If that does not work you can go outside and breath the cold air. At night, a humidifier should be used.
Scientists have found the viruses that cause croup. One of them is the flu and scientists have made a flu shot. Measles also causes croup and there is a vaccine for that too.
Sources:
"Croup." Gale Encyclopedia of Children's Health: Infancy throughAdolescence.Encyclopedia.com, n.d. Web. 01 Mar. 2017.
"Croup - Johns Hopkins All Children's Hospital." Croup - Johns Hopkins All Children's Hospital. N.p., n.d. Web. 01 Mar. 2017.
"Search Results." Mayo Clinic. N.p., n.d. Web. 01 Mar. 2017.
Nichols, Hannah. "What Is Croup? What Causes Croup?" Medical News Today. MediLexicon International, n.d. Web. 01 Mar. 2017.