Julia Ybarra, a registered nurse with Nomi Health, administers a booster dose of a Covid-19 vaccine to a patient during a City of Boulder vaccine clinic at the Boulder Public Library on Sunday, Nov. 21. Credit: Anthony Albidrez

As the U.S. underwent its most intense wave of Covid-19 illnesses and deaths in winter of 2021, there was one virological silver lining: Influenza all but disappeared. Now officials are worried about what a potential uptick in flu cases could mean for public health.

In its report on the 2020–2021 influenza season (which ran from late September to late May), the Colorado Department of Public Health & Environment concluded that the season “was markedly less severe than previous seasons.” 

During this time, the state recorded 34 hospitalizations associated with influenza, compared to 3,546 during the previous season, according to CDC data. The state’s flu death toll also fell, to six people. (Some 152 Coloradans died from the flu in the 2019–2020 season.) And for the first time since 2013–2014, there were no deaths in the state among residents younger than 18.

Last month, Boulder County Public Health released a statement warning about rising flu cases among Boulder residents ages 18-25, including two hospitalizations. 

“We are highly concerned about the potential impacts from a more active flu season,” said Carol Helwig, communicable disease control coordinator for Boulder County Public Health. “The surge in people impacted by Covid-19 illness in Boulder County over the past few weeks is already creating a substantial strain on hospitals, clinics and our whole health care system, and an active flu season could create an even greater strain and challenges.” 

An analysis of the CDC’s FluView data bears out Helwig’s concern. During the course of last year’s entire flu season in Colorado, 14 positive test results were reported after more than 66,000 tests. This season, the state has already reached 18 positive results from roughly 10,000 tests.

The state has reported only one flu-related death so far this season, compared to five at this point in 2019–2020.

In Boulder County, there have been four hospitalizations related to the flu this season.

The Colorado Department of Public Health & Environment found that public health safety measures related to the Covid-19 pandemic like masking and social distancing helped mitigate the spread of viral respiratory pathogens not related to Covid-19, including influenza. 

As with Covid-19, vaccination is also an important tool in the effort to curb widespread transmission of the flu. CDC data shows that Colorado’s flu vaccination rate was virtually the same last season as it was before the start of the pandemic (55.4% versus 55.5%, respectively). Boulder County Public Health urges everyone six months or older to get their flu shot as soon as possible.

For more information on getting a flu vaccine in Boulder County, visit Boulder County Public Health’s immunization resources, which include a list of free vaccine providers.