The bird flu may be entering a dangerous new phase. The risk that any given person will be sickened or die remains low, but the risk of this virus mutating into the next human pandemic is high enough to warrant action. That starts with much more aggressive measures to test and contain infected dairy herds.

“If we really don’t want this to come into people, we need to do something about the cows,” says Seema Lakdawala, an immunologist at the Emory University School of Medicine. And she’s right.

Every time the virus reaches a new host — bovine or human — it makes billions of new copies of itself and increases its odds of hitting on the combination of mutations it needs to start the next human pandemic.

Ever since the virus known as H5N1 was identified in dairy cows in March, it’s continued to spread around the country — turning up in 200 herds over at least 14 states. In Texas, a study of wastewater in September found the virus in 10 out of 10 samples. Scientists can’t be sure whether those signals are coming from animals or from people.

So far, only 14 people in the U.S. have tested positive for H5N1, but there’s very little testing taking place. A hospitalized patient in Missouri tested positive in September despite no known contact with birds or cows. A household contact of that person also tested positive. Two health care workers who were in contact with the hospitalized person reported flulike symptoms. (The workers recovered before they could be tested.)

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H5N1 has been killing domestic chickens and wild birds and threatening people since the 1990s. The current outbreak dates to late 2022 or early 2023, when it started killing mammal species around the world, including seals, sea lions, grizzly bears, foxes, cats, mice and mink.

In previous human outbreaks, H5N1 had a staggering 50% fatality rate. This latest variant appears to be milder, but as we saw with Covid, even a disease that’s less than 1% fatal can be devastating if it circulates widely.

Big gaps remain in scientists’ knowledge. They still don’t know if infected cows become immune or can get re-infected. They don’t know if some infections might be asymptomatic. They don’t know how long diseased cows can spread the virus.

We urgently need answers to those questions. That starts with a more aggressive posture from the U.S. Department of Agriculture, the Centers for Disease Control and Prevention, and state public health departments.

Most of the surveillance is currently being done through testing of pooled milk, said Lakdawala. While some infected cows show symptoms, others might be spreading the disease silently. Farmers whose pooled milk tests positive need the tools to follow up by testing each individual cow, enabling them to isolate the infected ones and stop further spread.

She said dairy farms often use machines to milk cows and these aren’t always sanitized. Research that her group has done showed that the virus persists for long periods of time on milking equipment. She says contaminated equipment is likely one of the primary routes of spread among cows.

She’s also worried about the contaminated milk that farmers have been sending down the drain. “We have reports that these cows can have as much as 100 million infectious virus particles in one little milliliter of milk,” she said. And dairy farmers are pouring away gallons. The infectious milk goes to manure lagoons, she said, where solids are separated out and liquids can go into irrigation fields. In some cases, they’re finding dead cats on these fields. (Cats are known to be susceptible to H5N1).

It’s possible to kill the virus by treating the milk with high heat, but farmers don’t always have the means to do that, she said, so her lab is working on less expensive ways to sanitize infectious milk before it’s discarded.

And cows are still being moved across the U.S., sometimes without sufficient testing, she says. “We need to have a temporary ‘stay at farm’ order where cattle are just not moved while we figure out which cattle are infected,” she said.

More testing in humans would also help monitor the situation, said epidemiologist Jennifer Nuzzo, director of the pandemic center at Brown University. “We’re not getting ahead of the problem.”

“The fact that farm workers continue to be infected in the course of their jobs means that this is a serious public health situation,” she said. “I don’t think we should wait for a farm worker to die before we get concerned about protecting them.”

The risk of a more dangerous variant emerging will rise with the start of the fall flu season. Different influenza viruses can infect the same person and exchange genetic material. Something new could emerge with the ability to spread easily from human to human — “our worst-case scenario,” she said.

If this virus were spreading in dairy farms in China rather than the U.S., she said, we’d be demanding more testing, more transparency about the extent of the disease, and the details of those mysterious cases in Missouri. “I’ve gotten assurances from CDC and local health that they’ve done contact tracing 1/8but3/8 there’s no data about it,” Nuzzo said. If we want other countries to be transparent with us, “we need to be transparent.”

Right now, scientists can’t put a number on the odds this virus will cause the next pandemic. But the risk goes up the longer the virus circulates in domestic animals. It’s time to lock down the cows.

F.D. Flam is a Bloomberg Opinion columnist covering science. She is host of the “Follow the Science” podcast.

A look at some of Friday’s top high school football games involving East Metro and western Wisconsin teams:

Mounds View (3-2) at East Ridge (3-2), 7 p.m.

Mounds View, Forest Lake and Stillwater are all 3-1 in Metro East subdistrict play heading into the final week of this subdistrict’s competition. Forest Lake and Stillwater are both heavy favorites Friday, meaning Mounds View likely needs to win if it aims to grab a piece of the “conference” championship. East Ridge won’t make it easy. OUR PICK: Mounds View 27, East Ridge 24

Anoka (3-2) at Centennial (3-2), 7 p.m.

St. Michael-Academy, Blaine, Centennial and Anoka are all dueling for second place in the Metro North subdistrict and, with it, a likely No. 2 seed in the Class 6A bracket. The winner of Friday’s game guarantees itself a a first-round home playoff game, and will likely receive a top-three seed. Centennial stopped Anoka’s high-flying passing attack a year ago, and appears to be finding its groove this season at just the right time. OUR PICK: Centennial 20, Anoka 16

Cretin-Derham Hall (1-4) at Mahtomedi (1-4), 7 p.m.

A game between 1-4 teams making the list? Absolutely, given what’s at stake. It’s a down year for Class 5A, Section 4. Tartan, Cretin-Derham Hall and Mahtomedi are all struggling, yet at the top of the list for potential byes and even the No. 1 seed in section playoffs. With a win at Mahtomedi, Cretin-Derham Hall would have wins over both, perhaps cementing itself in that top slot. Mahtomedi lost to Tartan last week, but a win over Cretin-Derham Hall to pair with a win over Central would muddy the conversation. OUR PICK: Cretin-Derham Hall 22, Mahtomedi 20

Johnson (2-2) at St. Agnes (3-2), at Concordia-St. Paul, 7 p.m.

A game chalk-full of playmakers on both sides if everybody is healthy, look for points to be scored in a potential fun one with Danny Plamann (St. Agnes) and Justice Moody (Johnson) matching one another with massive receptions. OUR PICK: St. Agnes 35, Johnson 22

WISCONSIN

Menomonie (5-1) at New Richmond (6-0), 7 p.m.

The Tigers rallied from a 9-point fourth-quarter deficit last week to snap Rice Lake’s 18-game winning streak and essentially lock up at least a share of a Big Rivers Conference title. But the only way for New Richmond to guarantee the throne all to itself is to topple Menomonie, which is still in the title hunt and has scored 35-plus points in four of its past five games via a balanced offensive attack. But after the Tigers proved they could slow down the Warriors’ ground game, there’s no reason to doubt New Richmond’s defense. OUR PICK: New Richmond 24, Menomonie 14

Blind drunk at closing time, Rona — a bright, late-20s graduate student majoring in biology — has again pushed her luck and, literally kicking and screaming, provoked the bartender into tossing her out of a London pub onto the sidewalk. Her purse’s contents scatter and roll. She has been here before, or thereabouts.

“The Outrun” tells her addiction and recovery story with clear-eyed and nicely unpredictable swerves. Saoirse Ronan does subtly spectacular work in every phase of this character’s odyssey. Rona is based on Amy Liptrot, whose memoir has been lightly fictionalized but not falsified in the script co-written by Liptrot and director Nora Fingscheidt. It’s a consistently absorbing movie, visually vibrant nearly to the point of self-consciousness, its blues and greens and hot neon dance-party memories colliding and coalescing throughout.

The narrative intersperses Rona’s heady London years with later parts of her life on the starkly beautiful Orkney Islands off Scotland’s northeastern coast. Watching “The Outrun,” its title referring to outlying farmland pasture, I found myself asking the Saoirse Ronan question that has come up many times and many films previously. What’s the secret to her easy gravity, the calm and storm and back again so effortlessly managed? That precise emotional stillness suddenly giving way to pure, kinetic expressivity?

Maybe there is no secret. Maybe Ronan, piercing blue eyes aside, simply is one of those actors who learned on camera, a lot, as a preteen and then became an adult and a famously reliable and compelling performer in the bargain. British roles, American parts, comedies, dramas, contemporary work, period pictures, all of it. Ronan’s camera presence has a studious air to it, sometimes. At her best, though, it’s careful listening and watching. In “The Outrun” she’s giving one of her truest, cleanest portrayals, which is an interesting paradox, since Rona is both a mess and, later, a conduit for reflection, her own and the audience’s.

After a violent, half-remembered assault following the film’s opening pub sequence, Rona returns to the Orkney Islands where she grew up. Recovery will not be easy, she realizes. Her alcoholism has informed her early adult years, indelibly. At one point, later than we want to hear it, she says with terse clarity, like a death sentence: “I can’t be happy sober.” The film doesn’t end there, but “The Outrun” makes nothing easy, or pat.

Rona’s sheep-farmer father (Stephen Dillane, excellent) lives in a mobile home at cliff’s edge; his mental health challenges have led him, reluctantly, in and out of institutions. Separated, Rona’s mother (Saskia Reeves, exceptional at subtle indications of how the past feeds the present) has turned to God for solace and purpose. Rona finds herself at odds with both parents. She’s itching to return to London, and all too plainly itching to drink again.

Counting her days of sobriety, she finds a makeshift Orkney community among the nonprofit Royal Society for the Protection of Birds, aka the RSPB. She’s assigned to study the prospects and conditions for a locally rare species, the corncrake, and canvases the local residents for their assistance. “The Outrun,” blessedly, treats the wildlife preservation activities the way director Fingscheidt treats everything else in Rona’s uncertain life: vividly but matter-of-factly, without a lot of fuss. Rona gradually rediscovers the things she loved about the islands as a girl, while discovering new ones. Part of the movie takes her to another, smaller Orkney Island, Papa Westray, where she relishes the isolation, the crazy gales and the joys of a swim in incredibly cold water.

The flashback interweaves of “The Outrun” recall Cheryl Strayed’s memoir “Wild,” the film version of which starred Reese Witherspoon. “The Outrun” has the edge, I think, in its editing acumen; in an eyeblink, we’re thrown back into Rona’s earlier life, and self, in London, with a boyfriend (Paapa Essiedu) increasingly overmatched by Rona’s addiction. In her character’s jagged-edge extremes, Ronan’s performance bears down, fiercely, without extraneous flourishes — in a heartbreaking leap, or stumble, her Rona trades raging belligerence (“You’re trying to tame me! You’re trying to control me!” for worlds of hurt found in a single line (“Whatever I did, I’ll never do it again, I promise”).

It’s not always easy to witness. But recovery stories that go easier are usually the ones lying about what’s happening, and how someone got there.

‘The Outrun’

3 stars (out of 4)

MPA rating: R (for language and brief sexuality)

Running time: 1:58

How to watch: In theaters Oct. 4

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