Some New Orleans residents are calling it the "Katrina Cough" --- a general upper respiratory irritation afflicting people returning to their hurricane-ravaged city.

What's causing the cough is a bit of mystery and no one is sure how widespread it is. But doctors says the trend is not a good sign, especially for people who already suffer from respiratory ailments like asthma, bronchitis and allergies.

"It is definitely more noticeable," said Dr. Robert Beckerman, professor and chief of pediatric pulmonology at Tulane Hospital for Children in New Orleans. "The allergy season has started earlier than usual. I have seen more children with coughing and rhinitis than in years past. I admit I have asthma and have had to double up on my meds after reconstruction work on my home."

Beckerman said the cough is probably caused by a mixture of several unfortunate events occurring at once: recent spells of dry, cool weather that can trigger asthma, plus lots of dust in the air caused by all the reconstruction. Added to that are homes covered in mold, a known allergy trigger.