An infectious disease doctor at Yale-New Haven Health says he is concerned over the increase in cases of walking pneumonia and whooping cough among children.

Both highly contagious pulmonary infections can cause airways to swell and lead to people having trouble breathing.

The Centers for Disease and Control has issued an alert over the surge in cases of walking pneumonia in children younger than 5 years old.

The lung infection is usually caused by mycoplasma bacteria.

"This has been the worst season in over a decade. The fact that this is now hitting a much younger age group than usual is certainly a concern because this is a group that is more vulnerable," says Dr. Scott Roberts.

Roberts says symptoms of walking pneumonia are cough, low fever and muscle aches. He says the problem is that people with walking pneumonia normally feel well enough to go to day care, school or other congregate settings.

However, due to advanced testing, doctors can diagnose people more accurately and earlier.

"We have a good treatment for this. We have an antibiotic…It's really important to get them in and we can treat it right away," says Roberts.

Cases of whooping cough, also known as pertussis, are five times higher than they were a year ago.

Roberts says getting antibiotic treatment started early will clear up the infection early.