EL PASO, Texas -

Seasonal illnesses are as much a part of winter as snowmen and hot chocolate.

Houston is feeling the effects of one particular virus -- and we're not talking about the flu.

Respiratory syncytial virus -- RSV -- sends about 125,000 American infants to the hospital every year. Texas Children's Hospital reported more than 600 cases in December -- up about 40 percent from the year before.

"It's always something that we need to worry about," said Dr. Brandy Yeary of Sierra Providence Medical Partners. "It's an illness that can have devastating consequences."

The Texas Department of State Health Services reported in December 2013 about one-fifth as many RSV cases as in December 2012. Statewide December reportings were about one-third of what they were a year ago.

"Disinfecting toys and making sure that they adhere to office procedures or daycare procedures and policies about keeping infants at home if they've had a fever or any other type of respiratory illnesses," Yeary said.

RSV is the leading cause of pneumonia in kids younger than one, according to Centers for Disease Control and Prevention. Most children get RSV at one time or another before their second birthday. Otherwise healthy people generally recover in one or two weeks.

Symptoms include a runny nose, decreased appetite, coughing, sneezing and a fever. Patients are usually contagious less than a week. RSV spreads through particles in the air and generally hits about half of other family members.

"When you think of someone, especially infants and young children as they're building their immune system, they have a lot of thing to rev up in terms of antibodies and things of that nature," Yeary said.

RSV vaccines are limited, Yeary said. There is a drug that can prevent but not cure the virus. Your best bet, as always, is washing your hands and covering your mouth.