Add another public health crisis to the toll of the new coronavirus: Mounting data suggests that domestic abuse is acting like an opportunistic infection, flourishing in the conditions created by the pandemic.

There was every reason to believe that the restrictions imposed to keep the virus from spreading would have such an effect, said Marianne Hester, a Bristol University sociologist who studies abusive relationships. Domestic violence goes up whenever families spend more time together, such as Christmas and summer vacations, she said.

Now, with families in lockdown worldwide, hotlines are lighting up with abuse reports, leaving governments trying to address a crisis that experts say they should have seen coming.

The United Nations called Sunday for urgent action to combat the worldwide surge in domestic violence.

“I urge all governments to put women’s safety first as they respond to the pandemic,” Secretary-General António Guterres wrote on Twitter.

But governments largely failed to prepare for the way the new public health measures would create opportunities for abusers to terrorize their victims. Now, many are scrambling to offer services to those at risk.

But, as with the response to the virus itself, the delays mean that irreparable harm may already have occurred.

As cities and towns across China locked down, a 26-year-old woman named Lele found herself entangled in more and more arguments with her husband, with whom she now had to spend every hour in their home in Anhui province, in eastern China.

On March 1, while Lele was holding her 11-month-old daughter, her husband began to beat her with a high chair. She is not sure how many times he hit her. Eventually, she said, one of her legs lost feeling and she fell to the ground, still holding the baby in her arms.

A photograph she took after the incident shows the high chair lying on the floor in pieces, two of its metal legs snapped off — evidence of the force with which her husband wielded it against her. Another image documents Lele’s injuries: Nearly every inch of her lower legs was covered in bruises, a huge hematoma blooming on her left calf.

Lele — her full name is not being used for her safety — said that her husband had abused her throughout their six-year relationship, but that the COVID-19 outbreak made things far worse.

“During the epidemic, we were unable to go outside, and our conflicts just grew bigger and bigger and more and more frequent,” she said. “Everything was exposed.”

As quarantines take effect around the world, that kind of “intimate terrorism” — a term many experts prefer for domestic violence — is flourishing.

In China, a Beijing-based NGO dedicated to combating violence against women, Equality, has seen a surge in calls to its help line since early February, when the government locked down cities in Hubei province, then the outbreak’s epicenter.

In Spain, the emergency number for domestic violence received 18% more calls in the first two weeks of lockdown than in the same period a month earlier.

“We’ve been getting some very distressing calls, showing us clearly just how intense psychological as well as physical mistreatment can get when people are kept 24 hours a day together within a reduced space,” said Ana Bella, who set up a foundation to help other women after surviving domestic violence herself.

On Thursday, French police reported a nationwide spike of about 30% in domestic violence. Christophe Castaner, the French interior minister, said he had asked officers to be on the lookout for abuse.

“The risk increases due to confinement,” he said in an interview on French television.

In Spain, with the help of women’s associations, The New York Times contacted women stuck at home with an abusive husband or partner and conducted interviews over WhatsApp.

One of them, Ana — who asked that her full name be withheld — shares an apartment with her partner and says he has been regularly abusing her. He insists on total surveillance at all times. If she tries to lock herself in a room, he kicks the door until she opens it.

“I can’t even have privacy in the bathroom — and now I have to endure this in a lockdown,” she wrote in a message sent late at night, to hide the communication from her husband.

Judith Lewis Herman, a renowned trauma expert at Harvard University Medical School, has found that the coercive methods that domestic abusers use to control their partners and children “bear an uncanny resemblance” to those that kidnappers use to control hostages and that repressive regimes use to break the will of political prisoners.

“The methods which enable one human being to control another are remarkably consistent,” she wrote in a widely cited 1992 journal article. “While perpetrators of organized political or sexual exploitation may instruct each other in coercive methods, perpetrators of domestic abuse appear to reinvent them.”

In addition to physical violence, which is not present in every abusive relationship, common tools of abuse include isolation from friends, family and employment; constant surveillance; strict, detailed rules for behavior; and restrictions on access to such basic necessities as food, clothing and sanitary facilities.

Home isolation, however vital to the fight against the pandemic, is giving still more power to the abuser, Hester said.

“If suddenly people have got to be at home,” she said, “that gives him an opportunity, suddenly, to call the shots around that. To say what she should be doing or shouldn’t.”

The isolation has also shattered support networks, making it far more difficult for victims to get help or escape.

In Europe, one country after another seems to have followed the same grim path: First, governments impose lockdowns without making sufficient provisions for domestic abuse victims. About 10 days later, distress calls spike, setting off a public outcry. Only then do the governments scramble to improvise solutions.

Italy was first.

Its lockdown began in early March. Soon after that, domestic violence reports began to rise, but there was nowhere for newly desperate women to go. Shelters could not take them because the risk of infection was too great.

So the government said local authorities could requisition hotel rooms to serve as makeshift shelters where victims could quarantine safely.

Spain announced its lockdown March 14; France’s began three days later. About two weeks later, with abuse reports soaring, officials there announced that they, too, planned to turn vacant hotel rooms into shelters, among other emergency efforts.

Eventually, the lockdowns will end. But as the confinement drags on, the danger seems likely to intensify. Studies show that abusers are more likely to murder their partners and others in the wake of personal crises, including lost jobs or major financial setbacks.

With COVID-19 ravaging the economy, such crises are set to become much more frequent.

© 2020 The New York Times Company