A sneezing chicken may indicate a serious health problem with your bird. But, chickens actually do not suffer from colds or flus. In poultry, symptoms of sneezing or wheezing are the result of a bacterial infection, known as Chicken Respiratory Disease.
Symptoms: sneezing, coughing, laboured breath, less eggs, lethargy and facial swelling.
It is quite contagious throughout the flock. If they start to find it hard to perform normal activities such as drinking, use and eye-dropper to help them drink water. Antibiotics are a good go-to. 2 Pak Avian Probiotic is a good one (see attached pic). Good luck!