Babies exposed to severe respiratory viruses have a higher likelihood of developing asthma as they grow older, new research suggests.

Treating these infants with medications that could change their immune response could prevent the development of the disease, they suggest.

Treating infants with medications that could change their immune response could prevent the development of asthma, researchers suggest.
(CBC)

According to researchers, infants who are infected with respiratory viruses have a much higher rate of asthma.

"Less than one in 30 people who don't suffer a severe respiratory infection as a baby develop asthma, but of those who do get these infections, one in five goes on to have asthma," said Mitchell Grayson, assistant professor of medicine in the Division of Allergy and Immunology at Washington University School of Medicine in St. Louis.

The research was published in the Oct. 29 issue of the Journal of Experimental Medicine.

In tests on mice genetically engineered to be susceptible to asthma, researchers exposed the animals to a  severe viral respiratory infection. They found the rodents did not react typically to infection. Instead, they experienced an allergic reaction similar to an asthmatic response.

The scientists believe that in humans, respiratory viruses deactivate the body's typical defence mechanism and create an allergic response. People who are infected with a virus gradually become over-sensitized to various substances and then go on to develop full-fledged asthma.

"In those people an allergic-type response could be part of their antiviral immune response. That sets them up to make antibodies against a lot of environmental substances, like pet dander or pollen, and they can go on to develop allergies or asthma," said Grayson.

The researchers note that asthma rates are increasing, and speculate that the surge in cases could be due to the higher density in urban areas which can spread upper respiratory viruses. "Increased population density, as well as other factors, may lead to increased transmission of respiratory viral infections," reads the study.

The Washington University researchers believe that halting the inflammatory processes that occur following a severe respiratory infection may be one way of halting the development of asthma in the future.