Christine Zimmermann is content marketing manager at Startup Institute. Startup Institute trains innovative and passionate people to get jobs and thrive at startup and scale up companies.

Catching the flu is miserable. The symptoms are clear: you wake up in the morning with a foggy brain, aching muscles and extreme fatigue — you are going to be down for the count for a week, but you know what you need to do to take care of it. There are other, more insidious afflictions that take hold more slowly, are harder to diagnose and more ambiguous to treat. This type of disease is often the most catastrophic.

The same is true of harmful employees within your company.

Underperforming, sarcastic or complaining. Unproductive and apathetic. Unwilling-to-compromise, or the perpetrator of an egregious act. These symptoms are likely to be clear and comprehensible to all members of your team. Whether the issue is cultural, or a misalignment of skills. It’s never pleasant to let anyone go, but when the decision is easy, the process can be too. Most importantly, your team gets it. They may even be grateful.

A toxic employee, on the other hand, can be like a cancer to a happy and thriving team, and they pose a serious risk to the success of the business. These people can take time to identify, are a challenge to get rid of and are extremely detrimental to your company’s culture.

Diagnosing the Problem

Toxicity is a subtle and subversive undercurrent through which the employee injects negative opinions about the company. It manifests in gossip and manipulation, and frequently vocalized critiques — not in the way of voicing a concern or constructive feedback of their supervisor, but under the radar, with the intent to influence their peers. When the solutions they suggest are not implemented, the toxic employee will attribute this to incompetency on the part of the team and leadership.

The toxic employee can often appear friendly, charismatic and might even be popular amongst their peer group. It’s possible that their skillset adds value to the team. They may have been great employees at one time, but soured on the job over time. Symptoms of toxicity aren’t overt, but they exist. These employees will abuse paid time off and privileges to work from home. They may hoard information in an attempt to emphasize their importance in the organization, and they’ll instigate gossip among peers.

Dealing with a Toxic Employee

Once you’ve identified an employee as toxic in your organization, the sad truth is that it’s unlikely they’ll be able to turn it around. Because the behavior is intangible and largely under the radar — perhaps more tonal than any clear offense that you can point to — it’s difficult to articulate as actionable feedback. This person sees themselves as indispensable to the team, and chances are slim that they’d be open to such feedback.

If this person were an underperforming complainer, you could let them go and your team would get it — they just weren’t a culture fit. But, in the eyes of their peers, they are a loved and respected contributor. It isn’t easy to let them go; you need to build a case. Document everything.

The minute you hear gossip or experience negativity, call a meeting with the employee and ask them to explain their actions directly. Don’t allow room for debate, simply state that you are aware of what is happening and that you will not tolerate the activity. Send a follow-up email detailing your discussion and expectations for change in writing. In rare cases, this can turn a person around, but more often the behavior will continue — and worsen. The employee must be let go swiftly.

Recovery

More challenging than finally ridding your organization of the toxic employee is damage control. Remember: these people were well-liked. By letting go of a person who your team believed to be a valued contributor, you risk their trust. It’s critical that you appreciate that this will be confusing and emotional, and communicate the news in a way that is sensitive. Be transparent about what the issues were and openly address questions without saying anything bad about that person.

Unfortunately toxicity can and often does spread. Reestablishing the trust of your team — which will be shaken to some degree — is the number one thing you can do to move forward.

Most importantly, remember that the culture and success of an organization goes top-down. If you want to cultivate a culture of passionate, driven and optimistic employees, then you can’t focus your energy on the negative people. Focus on developing your employees who exhibit this passion, drive and optimism. Give them the opportunities and feedback they need to grow, and show appreciation for what they bring to your team.

This is preventative care.