The surge of influenza outbreaks in Minnesota schools this month is an alarming reminder of how quickly this virus can spread in places where people are gathered.

During the first week of December, 14 schools around the state reported outbreaks, meaning 5% absenteeism or higher. A week later, the number of schools reporting this level of illness increased to 60. Health officials are also reporting a higher-than-usual number of kids requiring hospitalization.

This is a sobering place to be so early in the annual winter flu season, which usually stretches into March and typically peaks in February. Although imperfect, the flu shot, which is recommended for everyone over the age of 6 months, remains the best defense against the circulating virus. That reminder should not only spur parents into action, but also a federal agency — U.S. Customs and Border Protection (CBP).

CBP’s mission is to secure the nation’s borders. As part of that work, it takes migrants into custody, including young children and teens, holding them in crowded conditions ideal for spreading the flu virus. While these detainment facilities are generally near the nation’s southern border, the flu virus isn’t contained by fences or distance.

Outbreaks, no matter where they happen, threaten public health. Influenza vaccinations should be administered as soon as possible to those CBP takes into custody. Unfortunately, the agency’s leaders have been derelict in shouldering this vital responsibility.

This failure requires immediate remedy. It puts those in CBP’s custody at risk and creates a broader public health threat because of the ease with which the flu virus can spread. CBP employees, for example, could become ill with the flu and infect their families and communities.

A Dec. 16 letter signed by 65 members of Congress (including Minnesota Sen. Amy Klobuchar) underscored concerns about CBP’s flu shot inaction. Lawmakers have been urging the agency for months to vaccinate migrants but the agency continues to resist doing so.

CBP officials’ communications to Congress have cited “operational challenges.” Another reason: Its policy is not to hold detainees longer than 72 hours. Last week, CBP told an editorial writer that “we stand by our process” and said that other agencies, such as Immigration and Customs Enforcement, can provide “vaccinations as appropriate” to those in custody.

But the Dec. 16 letter reveals that this policy ignores recommendations from one of the world’s pre-eminent health agencies: the U.S. Centers for Disease Control and Prevention (CDC). The lawmakers’ missive said that the CDC for months has recommended vaccination “at the earliest feasible point of entry for all persons at least six months of age.”

The letter also states that prolonged detention times at CBP occur, with detainees sometimes held at its facilities for up to three weeks. Thus, CBP’s argument that vaccination isn’t necessary due to the short holding times simply doesn’t hold up. The same is true about its objections due to “operational difficulties.”

If it lacks staff, it can partner with local and regional public health agencies to provide the shots. Another option: Seek out medical volunteers. One organization, Doctors for Camp Closure, recently offered to provide shots and the agency declined.

The vaccination inaction reflects poorly on CBP and its leadership. It’s time to end the excuses and start taking the agency’s public health obligations seriously.