Chapel Hill, N.C. — Two North Carolina hospital systems have plans to limit visits by young people as a precaution to limit the spread of the H1N1 and seasonal flu viruses.

Young people are at greater risk for the H1N1 strain of the flu, according to Raleigh physician Dr. Allen Mask, because those over the age of 60 may have some resistance built up from earlier exposure in a vaccination or virus.

No one younger than 13 is permitted to visit the Newborn Critical Care Center, the Pediatric Intensive Care Unit and the Labor and Delivery Unit at UNC Hospitals in Chapel Hill, a spokesman said.

The Moses Cone Health System in Greensboro has banned visitors younger than 18 from all facilities, the Greensboro Record & News reported. The hospital put the measures in place because young people are more likely to catch the strain of H1N1 virus that is prevalent this year.

The H1N1 flu strain first identified in April is now responsible for almost all flu cases in the United States, according to the U.S. Centers for Disease Control and Prevention. It has caused more than 1 million illnesses so far, though most were mild and not reported.

A vaccine is expected to be available beginning in October, the CDC has said. That vaccine is designated for pregnant women, those who live with or care for children 6 months or younger, health care workers, people aged 6 months through 24 years, and people with chronic health problems or compromised immune systems.