Women and minorities were disproportionately sickened by the H1N1 flu strain in Utah.
Three-quarters of the people who died during the second wave of the virus' spread were women. And half the people hospitalized during the first wave were minorities.
But that doesn't mean gender and race are risk factors for flu complications on par with asthma or heart disease.
"It could just be chance," said Rachelle Boulton, an epidemiologist with the Utah Department of Health. She wrote about the disparities in a report on the 2009-10 flu season released Tuesday.
"We've looked at the cases and there isn't anything that sticks out that suggests women are more likely to die," she said.
Russ Miller, director of the respiratory intensive care unit at Intermountain Medical Center, agrees. While he noticed more women in the ICU for flu complications, he suspects it is because women are probably more likely to be admitted to the ICU for non-trauma reasons in general.
"Women live longer, long enough to come into an ICU with a medical illness as opposed to having a heart attack when they're 50 or 60," he said.
As for the higher rates of flu hospitalizations among minorities -- native Hawaiian and Pacific Islanders in particular had rates four to seven times higher than whites -- Boulton believes that has more to do with geography. The initial wave of flu cases were concentrated on the west side of Salt Lake County, where many minorities live.
The way Utah minorities were affected differs from the way it affects them nationwide, where Pacific Islanders had the lowest rates of hospitalization. Nationally, American Indians/Alaska Natives were hospitalized the most.
Boulton said Utah is working with other states and the Centers for Disease Control and Prevention to analyze data on American Indians/Alaska Natives who died from the flu to determine if they are genetically more susceptible. She said three American Indians from Utah have died since April of 48 total deaths.
The report said the flu season, which started in September, was one of the busiest ever in Utah, with 883 hospitalizations. By comparison, 250 to 500 flu-related hospitalizations are reported during a typical flu season.
Normally children under age 5 and people over 65 make up the bulk of the hospitalized, but this season the majority of stays were among people 5 to 49 years old. And the most severely affected -- the ones sent to intensive care or who died -- were often between the ages of 25 and 49.
The reason remains a mystery. Some have speculated that younger adults have a strong immune response that triggers more problems. Or, older people may suffer less because they were exposed to a similar strain in the 1970s and 1950s.
The second wave of the H1N1 flu season appears to be over, though health departments say the flu is still circulating and they continue to urge people to get vaccinated.
Some health departments may need to trash some of their supplies: Salt Lake Valley Health Department has about 8,400 doses that expire at the end of April.
Other departments only have doses that will last another year, assuming the virus doesn't mutate.
The Davis County Health Department has 8,000 H1N1 vaccine doses left to give, and it has been administering 1,000 doses a week through elementary schools.
The Weber-Morgan Health Department has 2,600 more doses and has also been holding clinics at elementary schools.