The physical and emotional exhaustion that turns into workplace burnout doesn’t happen overnight. It’s the result of hundreds of microstressors on the job that ultimately lead to employees hitting the wall, mentally checking out, or even quitting their jobs entirely.

And it’s happening to workers today at an alarming rate. As much as 89% of U.S. professionals surveyed in September by global consulting firm Korn Ferry, said they are suffering from burnout, and 38% said they were “burned out to a great extent.”

That exhaustion is having major consequences on the workforce. Employers, already facing a severe labor shortage, are under increased pressure to keep their workers from flaming out, even though employees are working longer hours during the COVID pandemic.

Workplace experts say employers should watch for behavior among employees, and negative patterns within their organizations that lead to chronic stress, and workers leaving. Here’s what happens right before burnout leads to quitting:

Employees look dead on Zoom

If managers find there’s little small talk before a meeting gets started, that could be a red flag. The same goes for an usually chatty employee who now keeps his camera off and contributes less to the conversation.

“If there’s lack of any spontaneous discussions or if someone raises a controversial subject and no one says much, you know they’re dead,” says Peter Cappelli, a professor of management and Wharton’s director of the center for human resources at the University of Pennsylvania.

That dead look on Zoom could be tied to boredom, Capelli says, and boredom is a big predictor of burnout. When people are working from home, they might take a break and go to the kitchen, but they don’t get the social interactions and engagement they would get in an office.

Research shows that people who have friends at work, or who feel supported by their peers, tend to stave off burnout better than those who don’t. Employees who feel like they belong and whose values align with their work also feel more energized, says Jennifer Moss, journalist and author of the Burnout Epidemic.

Leaders stop giving praise or appreciation—or they recognize the wrong people

If managers haven’t been saying thank you much, or giving positive feedback to their team, they just might be crushing workplace morale. In fact, lack of recognition is one of the root causes of burnout, says Moss.

Case in point: Employees at a McDonald’s in Bradford, Pennsylvania, complained about long hours and feeling under-appreciated before they walked out en masse in October, part of a broader trend of “rage-quitting” across the nation. Ad agencies are among numerous companies scrambling to prevent a white collar exodus as well.

“People are saying there is more to life than a paycheck,” says Gena Cox, an organizational psychologist and founder of executive coaching firm Feels Human Inc. in Tampa, Florida. “They want organizations to see them as the individuals they are.”

Managers should consider whether they’re doing enough to make people feel appreciated, she says, which is even more important today because of higher worker demands during the pandemic.

And when managers do recognize people publicly or hand out awards, they should make sure they’re fair about it. Discriminatory behaviors like sexism and racism can further demoralize the troops. “When the same people get promoted, particularly if they all act, sound, and look the same, we run the risk of being exclusive, which leads to burnout,” says Moss.

Irritation can also brew within teams when people who do sloppy work are rewarded, or when people are given awards instead of pay raises, according to Christina Maslach, a social psychologist at the University of California, Berkeley. Those feelings of unfairness can be “pebbles,” or small stressors that grow into major burnout factors.

Managers send emails on weekends and at odd hours—and don’t hire more people to pick up the slack

It’s no surprise that since we shifted to remote work in the pandemic, employees are feeling overtaxed. More than half of people surveyed by job site Indeed.com said they were working longer hours, making it much harder to unplug from work. Nearly a quarter of those people did not feel they could unplug at all from work.

When managers don’t respect boundaries between work and personal life— sending late-night or weekend emails, having unrealistic expectations about how much people should work, or not supporting caregivers’ needs for flexible schedules—that sends a subtle message to people that they cannot turn off work and that they’re cogs in a machine and not valued as human beings.

Overworking has a severe impact on our mental and physical health, says Moss, and when people become “overcommitted” at work, they’re at high risk for cynicism and exhaustion—and eventually burnout. Being overworked also leads to mistakes, poor productivity, anxiety, depression, and alcohol and drug use, according to Moss.

“You can handle chronic stress for one to two years, but then you hit a wall,” says Moss. “And it can be catastrophic

Leadership micromanages people

Employees who experience burnout are far more likely to say they feel micromanaged.

Peering-over-the-shoulder behavior might be okay for a short period of time, like when managers are training new employees or trying to boost underperformers, but it can have huge costs when it’s exorbitant. The micromanagers themselves are also at risk of burnout, because they don’t delegate and they end up working too much. Now, more than ever, people want autonomy in their jobs.

“They want more control, and to feel they have a greater sense of purpose and self-actualization,” says Cox.

Leaders aren’t about talking how people really feel

If managers are telling employees that the company values their mental health, but aren’t regularly asking them how they are feeling or what support they need, that could be a problem. As much as 90% of U.S. workers surveyed by Ernst & Young in October said empathetic leadership leads to higher job satisfaction, and 79% said it decreases employee turnover. And lack of empathy from a boss is a key reason why more than half of those surveyed said they quit a job.

Regular check-ins can be helpful, and managers should get informed about mental health, mental illness and the impact of chronic stress on their employees, says Moss. They should know how to have a conversation and provide support tools to workers.

Workers start having side conversations

If an employee doesn’t feel comfortable talking about their mental health or work frustrations with a manager or leader, they’ll start to talk privately with their peers. It lets them blow off some steam and find out if similar behaviors are eating at other people too, says Cox.

“They are going to one another for some mirroring, and they might be talking less to their managers,” Cox told Fortune, referring to the need to see their own frustrations, experiences and emotions reflected in their peers. This is especially true if the employees do not feel safe expressing their concerns to managers.

Managers should be paying attention and talk with people who have special relationships and trust with team members. Cox calls them “culture carriers,” and says it’s important for managers to connect with them to understand what’s happening within the group, and what people are concerned about.

Workplace experts say it’s vital for employers today to identify early on the signs that a team may be on the verge of burnout and how the leadership can unknowingly drive them there. Pay attention to people’s demeanor, noting whether they lack enthusiasm, and to whether people are complaining about work to each other privately. Leaders should also note whether they have unrealistic expectations about workloads and if managers aren’t empathetically connecting with or appreciating people. It’s vital for organizations to ensure employees don’t slide into burnout.

“Once a person becomes burned out,” Cox says, “it’s almost impossible to turn that around.”