Me too.. am watching the girls like a hawk.. so bad for my nerves!
Ava thinks it's a funny joke to cough then say OH NO COUGH cos then Z copies... argh kids i love you but really... no fake coughs PLEASE!
The cough is only a later symptom. Look out for runny noses, fever, sneezing and loss of appetite (you know all the things that look like hay fever as we head further into spring... doh!). If you get concerned, your GP can do a swab to test for it, and put them on a dose of antibiotics early if they do have it which will greatly reduce the severity.