H1N1 is waning in Minnesota, and it's anyone's guess whether another outbreak will occur this winter. But one thing is clear from the current outbreak -- it caused a lot of severe pneumonia cases.
The cases pushed some hospitals to their limits this fall, as they struggled to find enough beds and ventilators during the peak of the pandemic.
Severe pneumonias were very common in HCMC's intensive care unit this fall. Just a few weeks ago half the unit's 36 beds were filled with H1N1 pneumonia patients on ventilators, according to Con Iber, a lung specialist at Hennepin County Medical Center in Minneapolis.
Most of those ICU patients were young adults and middle-aged people.
"We have several people who have been on a breathing machine for well over a month, because of the severity of their pneumonia," said Iber.
Severe pneumonia ravages the lungs.
"There's so much damage to the lining of the airways in some cases, that the injury resembles chronic conditions where there's loss of cilia, conditions like cystic fibrosis," said Iber.
Bacterial pneumonias are common with influenza. The flu virus damages the mucus lining of the air tubes, making that area much more susceptible to bacterial infection.
Children and young adults are the ones most at risk for severe pneumonia resulting from H1N1.
Usually these complications develop mostly in people over 65. But with the new pandemic strain of flu, children and young adults have been the ones most at risk for severe illness.
"We're definitely seeing some significant pneumonias, some kids needing chest tubes, needing ventilators, children that are in-patient longer with some pretty significant pneumonias in both lungs," said Patsy Stinchfield, director of infectious disease at Children's Hospitals and Clinics of Minnesota.
Children's has treated 49 kids with H1N1 in its intensive care unit since April. Stinchfield estimates about half of those children had pneumonia.
"What we're seeing nationally is very similar to what we're seeing here at Children's," said Stinchfield.
Anneliese Preus, 15, of Maple Grove, spent 15 days at Children's in October.
The rest of her family got sick with H1N1 at the same time and recovered. But Anneliese developed a nasty pneumonia within a day of her first symptoms.
Doctors gave her antibiotics her first night in the hospital. But by the next morning they had to hook her up to a breathing machine that forced air into and out of her lungs. Her mother Jody said Annaliese deteriorated rapidly.
"They felt about one-third of her one lung was actually working. And when you would hear her breathe it was just a real quick, short little breaths," said Jody Preus. "So you knew she was needing a lot of help and a lot of antibiotics."
Annaliese doesn't remember much about the first week of her hospital stay. But she does remember her second week, largely because of the pain she endured when doctors inserted a tube into her chest to drain her infection.
It has been five weeks since her hospital stay, and Annaliese is just beginning to feel good enough to resume some of her activities.
"It took me awhile to get my energy back," she said. "I'd be so tired by the end of the day. But now I'm getting my strength back. That's the hardest part."
Annaliese is a runner and a soccer player. Her already tiny frame is now 21 pounds lighter due to her pneumonia ordeal.
She also developed laryngitis, and couldn't speak for several weeks. You can still hear the weakness in her voice. For that reason, she had to drop out of choir.
Annaliese just started doing some warmup exercises with her basketball team. But her doctor doesn't want her to play in a game until at least February.
"It's a little frustrating because I want to be out there playing," she said. "But I'm just glad to be here."
Lab tests eventually confirmed that Annaliese had a bacterial pneumonia caused by Staphylococcus aureus, which is very common in Minnesota.
That's just one of several types of bacteria that can cause lung infections. Health officials in Denver recently reported a large spike in pneumonias caused by Streptococcus pneumoniae.
So far the Minnesota Department of Health hasn't seen a spike in pneumonias related to that bacterium. But the agency says it is tracking the situation closely, because the trend in Denver is troubling.
There is a vaccine that protects against the most common strains of pneumococcus. The vaccine is recommended for anyone over age 2 with chronic health conditions, and all adults over age 65.