Babies and small children who develop severe respiratory infections in winter probably have a genetic susceptibility to the illness, British researchers said on Monday.

Bronchiolitis, an infection of the small airways of the lungs, is caused by the respiratory syncytial virus (RSV) that most children get by the time they are two years old.

It is the leading cause of hospital admissions in young children, causing breathlessness and wheezing and in some cases pneumonia.

Until now doctors did not know why it afflicted some children more severely than others, but new research by scientists at the John Radcliffe Hospital in Oxford shows it could be due to a gene mutation.

"These findings provide the first evidence of a genetic susceptibility determinant for RSV bronchiolitis," Dr Jeremy Hull said in a study published in the journal Thorax.

Hull and his team uncovered the link by studying 117 families with children who had severe cases of the illness between 1992 and 1999.

(From ChinaDaily)