How bad will flu season be? U. of C. researchers have had an idea for months
if you’re wondering just how bad this year’s flu season will be, the University of Chicago has a prediction for you — worse than average, but better than last year’s major siege of the achy sniffles.
And they’ve known that since this summer.
In a paper released Wednesday and published in the journal Science Translational Medicine, the university’s researchers described the development of a new model for predicting the yearly flu season “significantly earlier” than past efforts.
Their predictions have consistently proved accurate, the study’s authors said. Using historical data, their new model accurately forecast the total number of cases for every U.S. flu season from 2002 to 2016. It also correctly predicted the 2016-17 season before it began last year.
“Our analysis for this year showed that the virus is already changing in a significant way,” said Mercedes Pascual, who holds a postdoctorate degree in ecology and evolutionary biology and is the senior author of the study, in a statement. “We predict an outbreak that is above average but moderate, not severe, because last year was such a bad season.”
Predicting just how severe a flu outbreak will be from year to year has been tricky business, experts say.
One reason why it is so hard to predict how bad a flu season will be is because flu strains change from year to year.
At present, two major methods of forecasting seasonal flu exist: The first tracks how the virus might evolve; the second predicts how many incidences of infection might occur within a given season.
The former model can be useful for predicting evolutionary changes in flu virus for the coming transmission season but not how many people might be infected, or when. The latter can accurately forecast peak timing of epidemics and the virus’ spread, but only once the flu season has begun.
U. of C. researchers’ model accounts for both evolutionary changes and accurate tracking of the virus’ spread as early as the preceding summer.
One indicator that experts watch for is how badly the flu has gone over in Australia, where winter is already winding down. There, residents saw a particularly bad outbreak this year, prompting concern in the U.S. that the same could happen here.
“It’s always hard to know what that means for us,” said Dr. Marielle Fricchione, medical director of the immunization program at the Chicago Department of Public Health.
Enhanced forecasting would help public health officials better manage their limited resources to prevent flu each year, experts say. A model that predicts what strains might be predominant in a given year — and when — enables officials to make specific outreach efforts to groups most susceptible to infection far earlier.
“If we know when activity is going to peak or what strains are circulating, then we know which population to target in terms of education and resources,” Fricchione said.
Only 36 percent of adults in the city were vaccinated last year, down from 42 percent the year before. Last year, seniors were more likely than other adults to have been immunized, something the health department attributes to its efforts to reach the demographic through messaging and clinics at senior sites.
On Thursday, more than 200 people attended a pop-up clinic held in a gym at Bridgeport’s McGuane Park, where city employees administered free flu shots. Most of those vaccinated were older adults like Lois Kelly, of Bronzeville.
Kelly, 67, has asthma, elevating her risk of complications from flu. A retiree with young grandchildren, she said she gets vaccinated each year to protect herself and them. The fact that there are many free flu clinics doesn’t hurt, she said.
“I usually get it wherever it is free in the city: alderman offices, churches, now here,” Kelly said. “Actually, I still would get it, even if it were not free.”
Older adults, pregnant women, the chronically ill and very young children are especially susceptible to flu-related complications. In addition to asthma, those with heart disease and diabetes are also at high risk.
And flu can be fatal. According to the state Department of Public Health, influenza and pneumonia have been associated with an average of 3,500 annual deaths in the past 10 years in Illinois. Last year, in Chicago alone, close to 300 flu-related hospitalizations that required stays in intensive care were reported, resulting in 49 deaths, the city department of health notes.
Even individuals who are not among the “highest-risk” populations should make vaccination a priority, Fricchione said, as “everyone has contact with a high-risk person.”
Though flu season typically runs from late fall to early spring each year, illness in Chicago is generally highest from mid-January through late March, city data show.
During this flu season, the city health department will organize more than 70 flu clinics, including one in each ward. It’s made efforts to change clinic locations in neighborhoods that have historically seen low turnout — this year’s clinic at the Whole Foods in Englewood replaces one in the neighborhood that had been poorly attended in the past.
More people who are admitted to intensive care units in the city for flu-like illness live on the South and West sides, Fricchione said.
The easiest way to fight flu, most public health experts agree, is to get the shot early. The U.S. Centers for Disease Control and Prevention is excluding a nasal spray version of the immunization for a second year in a row, again citing concerns about its effectiveness.
City public health officials say now is an ideal time for vaccination, as the shot can take two weeks to work. Breaking away from work or school to get the shot can be inconvenient, but it is the best way to prevent illness, experts said. It’s also less inconvenient than having to miss weeks of work or school because of the flu.
“Every year there’s an epidemic of flu,” Fricchione said. “It’s one of those diseases that it’s not if it’s going to happen, but when it’s going to happen. That’s why we take it so seriously.”