“If you were a scholar studying China but were not allowed to visit, that’s where you had to be,” recalls Zia, adding that the centre was partly funded by the US government and had the reputation of being a CIA outpost. “Much to the jealousy of the PhDs and professors there, I had a visa to go to China.”

Before her book, Zia says, nobody had written in English about the people who endured the mass migration from Shanghai, which came close on the heels of another traumatic event: Japan’s invasion of China. “From the Hong Kong perspective,” says Zia, quoting a friend from the city, “everybody knows somebody who fled Shanghai. So why write about such a thing?”

Social stigma, too, was a factor: “These were people who had not joined the [communist] revolution and were seen as bad elements.”

When Zia set out to research her book about 12 years ago, she realised that the literary amnesia extended to the academic world as well.

“Until my book, not even one PhD or undergraduate thesis had been written on the human cost behind the exodus from Shanghai,” she says. “From the point of view of American scholars, there is a stereotype about people from Shanghai – that they are wily, arrogant, braggarts from China. So there’s a feeling among academics that they’re not worth studying.

“To think that everyone who left Shanghai was rich, snobby or a Kuomintang official was just not true. Everybody had a different reason to flee and went through an agonising process. And then, when they became refugees, even in the US, they were not welcome.”

Zia’s own mother fled Shanghai – and it took her 70 years to talk about the ordeal.

“She would always say it was a bad memory, clearly indicating she did not want to go into any details,” Zia says. “I think it’s typical of people who live through traumatic times – there are so many scars, they don’t want to open them up.”

Zia found it heart-wrenching, yet inspiring, to hear the stories of people who had lived through the Japanese invasion of Shanghai only to be forced into exile following the city’s tumultuous takeover by communist forces. She was struck by “how the human spirit rises to the occasion – how people had such a strong will to not just survive but also do something with their lives.”

Zia conducted more than 100 interviews for her book, talking to people in Hong Kong, China, Taiwan and across the US, Canada, Australia, South America, Southeast Asia, India and Africa.

One of her biggest challenges was to find living survivors of the exodus. This was a critical factor in her reporting, because the Kuomintang, which controlled Shanghai before the communist takeover, had destroyed the city’s official records.

“Another challenge was that I’m an American-born Chinese who grew up not speaking Chinese because my parents believed I would face racism if I did,” Zia says. “So for me, the question was: how do I write a book when I can’t read Chinese?”

Fortunately, Zia won a Fulbright fellowship that allowed her to live in Shanghai and Hong Kong for a year. Shanghai’s municipal archives, housed in the city’s main library, turned out to be an invaluable resource. There, Zia found many newspapers in multiple languages, including Dutch and German, that chronicled life in Shanghai leading up to the revolution.

Zia’s first impression of China back in 1972, at the height of the Cultural Revolution, was how clean the country was.

“There were barefoot doctors [farmers who received minimal medical training and worked in rural areas] everywhere, and no signs of vices such as prostitution and drugs, which cities like Shanghai were infamous for,” she recalls. “The impression I had was that China was working very hard to meet the needs of people with limited resources.”

What Zia did not see were the brutal effects of the Cultural Revolution, which the world was generally unaware of at the time. “I was shielded from that and only saw what the Chinese government wanted to show to foreigners like me,” she says.

Zia was born and raised in the northeastern US state of New Jersey at a time when Asian-Americans numbered “maybe less than 1 per cent of the population”, she recalls. “Most of them lived in ghettos such as Chinatown, Little India and Manila Town, and were not allowed to move into different parts of the state.”

Zia often heard people in her town telling her to “go back to where you came from”. Because the US was fighting wars in Korea and Vietnam at the time, people of Chinese and East Asian descent were often looked upon as the enemy.

“If you went to the movies or turned on the news, everybody who needed to be killed had an East Asian face,” Zia recalls. “Americans had no idea who Asians were or what countries they came from. We all tended to be lumped together in one group.”

At university, Zia plunged into a variety of social movements. She marched against the Vietnam war. She advocated for the civil rights of African-Americans. She identified with “all the inequalities around women rights”.

And when The New York Times, relying on slim evidence and sources with an axe to grind, published a front-page “special report” in 1999 about China’s alleged attempts to steal US nuclear secrets, Zia was outraged.

The 4,000-word report implicated Wen Ho Lee, a Taiwan-born nuclear scientist at the US government’s Los Alamos National Laboratory, as a spy. The story captured the nation’s attention, setting the stage for what, by all accounts, was a politically motivated witch-hunt by the FBI.

Lee was charged with espionage and his career was shattered (all but one of the 59 charges against him were subsequently dropped). In 2001, Zia teamed up with Lee to co-author a book, My Country Versus Me: The First-Hand Account by the Los Alamos Scientist who was Falsely Accused of Being a Spy.

To this day, Zia says, FBI agents are rewarded for finding Chinese spies, although no investigation has reached the level of notoriety that caused Lee’s suffering.

“This goes hand in glove with Islamophobia and the fear of anyone who looks Muslim,” Zia says, alluding to the racial and religious discrimination that continues to plague America.

Zia is not optimistic about the near-term prospects of Sino-US ties, which have lately been fraught with military and trade tensions.

“The nationalism and hostility that has grown in the world has found a home both in the US and in China,” she says. “But I feel optimistic in the long run that civilised people will seek to have a world of peace in which different countries can engage their differences in a peaceful manner.”