It usually starts with a runny nose.

Nothing out of the ordinary – just like a common cold.

But if left unchecked, an RSV (respiratory syncytial virus) infection can land your infant in the hospital, and this is the time of year to be concerned.

“November through March is the official season for RSV, but you never know when it’s actually going to come,” says Dr. Anne Van Garsse, a pediatrician with Pediatric and Adolescent Medicine in Lawrence. “It seemed to hit us about January, so we’re right smack in the thick of it right now.”

Although anyone can contract the highly contagious virus, infants are more prone to serious cases, especially those born prematurely or those with other health problems, such as congenital heart disease.

Symptoms are similar to signs of a cold: stuffy or runny nose, sore throat, wheezing and coughing, low-grade fever and earache. But the presence of copious mucous sets RSV apart.

“Infants less than 6 months of age are really the ones that get hit harder,” Van Garsse says. “Since they have smaller airways and smaller bronchial tubes, that mucous can actually plug their smaller airways.”

At Children’s Mercy Hospital in Kansas City, Mo., more than 1,200 infants have tested positive for RSV since the season started in November. Although it’s the leading cause of hospitalization in children under 1 – and the most common cause of viral death in children under 5 – there seems to be a lack of awareness about the virus, says hospital spokeswoman Jennifer Benz.

“It seems like most parents tend to hear all about flu, but it seems like a lot of new parents are not familiar with RSV,” she says. “It seems like the general public isn’t as familiar with it because all you hear about is flu, but our flu numbers aren’t even close. For the year, for flu, we’ve had 567 positives.”

As with pertussis, commonly known as whooping cough, there is no cure for RSV. Doctors simply must attempt to make infants more comfortable while the virus runs its course, which usually takes about two weeks.

Babies who test positive are given nebulized breathing treatments, consisting of saline and albuterol, to help relieve wheezing and loosen and thin their mucous. Those who still can’t get enough oxygen are admitted to the hospital, where they’re treated with the same method and given a steady oxygen supply while being closely monitored.

Premature infants and those with other serious medical conditions can receive regular injections of preventive antibodies during RSV season to stave off infection.

Van Garsse doesn’t have statistics but says the number of RSV cases in Lawrence this season seems about average based on the number of infants who have required hospitalization.

She advises parents of children who will be less than 6 weeks old during the season to see their pediatrician at the first sign of a cold. On Tuesday, Van Garsse saw a 4-week-old, a 5-week-old and a 6-week-old who just had snotty noses but were eating and breathing OK. But an RSV test confirmed the virus in all three patients, and she was able to start them on breathing treatments to reduce later misery.

Parents of older children – 6 weeks to 6 months – who seem to be getting a cold should simply call their doctor, who can ask more specific questions and decide whether an office visit is necessary.

Either way, parents need to be aware of the signs of RSV in order to keep their babies safe and comfortable during the viral season.

“Don’t hesitate to call your health-care provider. That’s what we’re here for,” Van Garsse says. “No question is stupid. We’re not tired of hearing questions about RSV just because we’re in the middle of RSV season.”