El Paso County's flu season will go down as one of the worst in years - in particular, hitting an adult demographic that typically fares best against the virus, county health officials say.
The same strain that caused the 2009-2010 pandemic came back with a vengeance this year, causing 99 percent of the 204 hospitalizations logged in El Paso County as of April 14, El Paso County Public Health records show.
While the worst appears to have passed - El Paso County, for example, has logged only three hospitalizations since mid-February - health officials again say there are lessons to be learned.
"It's a message for next year as well," said Lisa Miller, the Colorado Department of Public Health and Environment's state epidemiologist.
The county's number topped the 2009-2010 pandemic season that hospitalized 188 people, and it also comes on the heels of another difficult season last year, when 160 people were hospitalized.
The statistics are limited accountings of the full impact the virus can have, because they only account for instances where a person needed to be admitted into a hospital.
Still, few explanations are available for the increase, Miller said.
Officials touted a new vaccine this year - one that could guard against four strains of the virus, rather than the typical three.
But the strain that proved most prevalent in Colorado - the H1N1 variety - was already in the mix, she said.
"We can't explain influenza completely," Miller said. "We wish we could explain exactly why it behaves the way it does."
The virus also caused unusually more harm to people who normally are least affected by the virus.
More than half of the hospitalizations across Colorado affected people ages 18 to 64, according to state data compiled through late March, and similar trends occurred in the county.
Tallying adult flu deaths can be difficult, because other health conditions may play a factor. Still, the flu directly played a role in the deaths of two people at Penrose-St. Francis Health Services, while one person died at Memorial Health System, hospital officials said.
No children have died in Colorado this season - a change from last year, when five children succumbed to the virus.
Officials still say the vaccine is one the best ways to guard against the virus.
Final data on nationwide vaccination rates has yet to be released. In El Paso County, though, about 80 percent of the people hospitalized had yet to get the vaccine, the county reported.