The impending government shutdown could have big implications for how the US responds to the flu epidemic.

The US is facing one of the most severe flu seasons in years.

The shutdown would impact other health agencies, slowing down drug approvals, food inspections, and patients hoping to enroll in clinical trials.

The possibility of a government shutdown is looming over the country as the Senate tries to pass a funding bill.

The looming shutdown comes at a particularly bad time for public health officials, whose work could be limited especially when it comes to responding to the flu epidemic.

The US is facing one of the most severe flu seasons in years, with "widespread" instances of the bug appearing in 49 states. At least 21 children have died from the flu so far this season, which lasts until May.

"This year’s influenza season is proving particularly difficult" the Centers for Disease Control and Prevention deputy director Anne Schuchat said on Tuesday.

Having fewer resources to monitor the flu epidemic could make the season even more difficult. One complication: 63% of CDC staff would be furloughed, or placed on temporary leave.

Stat News reports that when the government shut down in 2013, the CDC had to shut down its flu program, meaning it was no longer able to track where the disease was spreading, coordinate with local public health officials, test samples coming in, or monitor infections at airports around the world.

Because the flu season is so bad, however, that could change whether the flu program is considered "essential," Stat reports.

The shutdown would impact other agencies under the Department of Health and Human Services as employees are put on furlough. At the Food and Drug Administration, a shutdown could slow down drug approvals and affect food inspections, and at the National Institutes of Health, it could mean that patients hoping to enroll in clinical trials won't be able to.