Although life-threatening cases of H1N1 are relatively rare, this flu strain is known to affect children, teenagers and young adults much more severely than regular seasonal flu. The Los Angeles Times offers guidelines to help parents for gauge when it is time to take a sick child to the emergency room:

So when should you take your child to the emergency room? Doctors say parents and guardians should assess how sick a child is in part based on experience.

“Is there something really different about your child that’s different from the seven or eight viral infections your kid gets every year? Those are the changes to look out for,” said Dr. Mark Morocco, associate residency director for emergency medicine at UCLA.

Warning signs include significant difficulty breathing; inability to drink fluids or urinate for more than six hours; change in the color of the mouth or lips; or unusual behavioral changes, such as a crying child who cannot be consoled, or a child who doesn’t wake up or walk or talk normally.

If any of those symptoms show up in children, parents should take them to the emergency room, Morocco said, noting that “respiratory infections are often things that are the most life-threatening in children.”

Lung inflammation is particularly dangerous to infants and young children because their airways are smaller. According to the California Department of Public Health, the flu virus replicates in the airways and lungs, causing them to swell. The inflammation makes it difficult for the lungs to work, reducing the body’s ability to take oxygen into the bloodstream.

The Times also notes that the CDC is encouraging doctors to prescribe Tamiflu or other antiviral drugs to patients hospitalized with severe flu symptoms. The agency points to a study that found that 25 percent of patients with severe symptoms did not receive antiviral drugs.