The star of ER and The Good Wife is back – as a doctor fighting to save humanity. She gives her bodyguard the slip to talk about our imperilled planet – and her love of Sussex A-roads

Before I meet Julianna Margulies, I spend three days staring at her bodyguard. He’s impossible to miss: one of those men whose every attempt to blend in flounders. Margulies and I are in Lille, judges at the Series Mania television festival, although our experiences differ a little. My cloak of anonymity allows me to roam the city unpestered. Margulies, however, has been a TV mainstay for 25 years, with roles in two juggernaut shows, ER and The Good Wife. Everybody knows who she is, hence Muscles.

He’s even there at the start of our interview, looming in the doorway of our room at the Chamber of Commerce. As I ease past and close the door, I ask if it isn’t a pain being constantly tailed. She smiles and says: “Three years ago, I was the guest of honour when they held this festival in Paris. When I get there, they say, ‘We have detail for you.’ I say, ‘Guys, I don’t need a bodyguard.’ But they won’t budge. We get to the hotel and I say to my bodyguard, ‘My husband and I are going out to lunch. You go home, please.’ So we left the hotel and I’ve never seen anything like it. People were everywhere. We backed into the hotel and my husband called the bodyguard and said, ‘We made a mistake!’ He said, ‘I know – I’m just around the corner.’”

Life’s not like that for Margulies in New York, though. “Honestly,” she says, “I move around just like you. I ride the subway and go to the grocery store – 100%. I don’t think anyone knows who I am, and I’m not just saying that because I’m humble. New York is like London: it’s metropolitan and nobody cares. Now, if I go to Ohio or a mall in Iowa, you can forget about it.”

Facebook Twitter Pinterest ‘Only six episodes – I love that!’ … Margulies in The Hot Zone. Photograph: Amanda Matlovich/National Geographic/Amanda Matlovich

Given her reputation for playing powerful women, I’m struck by how slight she seems, although this may be exacerbated by a recent bout of food poisoning. “It happened yesterday in the middle of a TV interview,” she says. “I ran into the men’s room. I’m projectile vomiting and I know they can all hear it. I’m mortified. But I went back and did the interview.”

Margulies, 52, is no stranger to France. Although she was born in Spring Valley, New York, to a ballet dancer mother and an advertising executive father (who helped develop Alka-Seltzer’s “Plop-plop, fizz-fizz” slogan), she bounced between countries as a child. First came Israel, then Europe. “Even though my parents were separated, my mom was like, ‘Let’s go to Paris.’ So he lived on the Right Bank and we lived on the Left.”

Two years later, they moved to Britain. “My dad was in London. We were in Sussex for three years and then we all moved back to the States. Then my mom moved us back to Sussex for another two years. Two years later, my dad moved back to London. It was a lot of back and forth.” Which part of Sussex? “Forest Row, darling,” she says in just about the right accent. When I tell her I have family who live nearby, she lights up and starts rattling off all the local A-roads.

Did this rootless upbringing affect her? “I hated it then, but I love it now,” she says. “I think kids always want to be the same as everyone else. I remember coming back to America and kids saying, ‘Talk, talk!’ – because my English accent was so thick. My middle sister had a weird French-English accent, and my eldest had a weird American-English-French accent, but mine was English.”

Facebook Twitter Pinterest Rift rumours … Archie Panjabi and Margulies in The Good Wife. Photograph: CBS Photo Archive/CBS via Getty

Margulies’ most memorable role has been in The Good Wife. At a time when TV was defined by the Don Drapers and Walter Whites – dark, brooding, male antiheroes – Alicia Florrick stood out. A subversion of the put-upon wife, Florrick was driven and complicated, as both a lawyer and mother. She could often be flat-out unlikable, getting a slap for betraying her boss in the final episode.

True, towards the end, the soapier elements started to overwhelm the show, and then it came to light that Margulies and co-star Archie Panjabi reportedly disliked each other so much that some of their scenes together had to be shot separately. Elements still clearly niggle: shortly after we meet, Margulies reveals that she hasn’t appeared on the show’s acclaimed spin-off The Good Fight because CBS isn’t willing to pay her more than a regular guest fee. “If Jon Hamm came back for a Mad Men spinoff,” she said, “or Kiefer Sutherland wanted to do a 24 spinoff, they would be paid.”

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It seems especially harsh given that Margulies was pivotal to every episode of The Good Wife. In just seven years, The Good Wife churned out 156 shows, 22 at a time, with Margulies front and centre throughout. Compare that to Breaking Bad, which had 62 episodes over five series, and Mad Men 92 over seven.

She has spoken before about working 14-hour days and being pumped full of steroids and vitamins whenever she fell ill, just so she could perform. This might explain the appeal of her new project, The Hot Zone, which only runs to six episodes. Margulies sighs. “Six. I love that. It’s a miniseries.”

Is this preferable to a network show? “On ER and The Good Wife, I got lucky with great writing. However, you can’t really make 22 home runs out of 22 balls. It’s so hard on the writers. But a miniseries gives writers time and you get to prepare.”

Facebook Twitter Pinterest Love diagnosis … Margulies in ER with George Clooney. Photograph: AF archive/Alamy Stock Photo/Alamy Stock Photo

In The Hot Zone, Margulies plays a real-life doctor named Nancy Jaax who is trapped in a race against time to stop an incurable virus from infecting all of humanity. It all sounds rather improbable but it’s rooted in fact, based on Richard Preston’s bestselling 1994 book of the same name. The Hot Zone was originally envisioned as a movie 25 years ago, to be directed by Ridley Scott and starring Robert Redford and Jodi Foster, until a rival producer cut the production off at the knees by rush-releasing the similar Outbreak.

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“I’m pleased it fell apart,” says Margulies. “The story is too vast to tell in a movie.” She found the book a page-turner and makes the same claim for the show. “You’re like, ‘Wait, what? What?’ Then you suddenly realise this all actually happened, and it’s still happening. More than 800 deaths from a single outbreak in the Democratic Republic of Congo since just last August.”

It’s a terrifying subject and it’s only getting worse, as a glance at recent headlines show: last week, the Guardian reported that the number of infected people in North Kivu province had reached 1,600. “We had Ebola on US soil and it’ll be on European soil at some point,” Margulies says. “It’s not a matter of if, it’s a matter of when. There’s still no protocol. There’s still no cure.”

Facebook Twitter Pinterest Don’t shake hands … Margulies as Dr Nancy Jaax in The Hot Zone. Photograph: Amanda Matlovich/National Geographic

Curiously, Ebola is sometimes credited with kickstarting Donald Trump’s political career. In 2014, as west Africa was buckling under the largest outbreak in history, two sick workers were flown back to the US for treatment. “And the schmuck who’s now in the White House said, ‘Don’t let those people back in our country.’” Margulies, an avowed liberal, uses Donald Trump poop bags to clean up after her dog. Trump tweeted about Ebola on a near-daily basis for three months, strengthening the differences between himself and Barack Obama. This, Margulies said, affected morale in the field.

“One of the doctors said to me, ‘Do you know what those tweets did for us? We were putting our lives on the line, and this rich asshole is texting not to let us back in the country when we’re there to protect our country.’ Ebola can have a 90% fatality rate. It can wipe out a village. It’s fatal. And they went to figure out how to get a cure, right, so that it doesn’t happen in the rest of the world?”

She laughs self-consciously. “Oh, I know way too much. I don’t want to ruin your life, but you’ll never see an infectious disease specialist touch their face, while a normal person will touch their face over 100 times a day. They also don’t shake hands. They either fist-bump or hip-bump or elbow-bump.” I apologise for shaking her hand on the way in. “Don’t worry, look at this,” she says, motioning towards a handbag stuffed with disinfectant.

Margulies has rarely returned to projects. She left ER while the series was in its prime, she won’t appear in The Good Fight, and shows no desire to step back on the network treadmill. Yet The Hot Zone does count as a return of sorts. Almost two decades after quitting ER, she’s back playing a medic.

“I don’t think I thought it through enough before I signed on,” she sighs. “In my head, it was scientific rather than medical, but I still had the hardest medical jargon to memorise. You don’t know what you’re saying. And then you’re in the hazmat suits with fans to keep the air circulated, so I couldn’t hear anything. I was in a panic every time they zipped me in.”

It doesn’t sound ideal, I say. “Never again,” she replies.

• The Hot Zone premieres in the US on National Geographic Channel on 27 May. It will screen in the UK later this year.