There’s an epidemic going around your office—and everyone is vulnerable. No, it’s not that dreaded springtime cold, but it is highly contagious: It’s called secondhand, or “transmitted,” stress, and you catch it from the people around you.

“Transmitted stress is when we experience the physiological response another person has to a stressor without experiencing the stressor ourselves,” says Dr. Mithu Storoni, author of Stress-Proof: The Scientific Solution to Protect Your Brain and Body. In other words, “Stress is contagious.”

Why? The theory is that transmitted stress evolved from our tribal heritage as a way of keeping us safe, Storoni says. If one member of the tribe spotted a threat or predator, they needed others to be alert in an instant. There often wasn’t time for an explanation, so our brains became wired to ‘feel’ and react to others’ stress. This response is helpful when the threat is life-or-death but creates unnecessary tension when it amplifies day-to-day stress and ripples through a modern office.

We’ve all been there: You’re feeling good about your day…until a coworker comes in worrying about their sales numbers or upset about an angry customer service call. Your mood dives as you begin thinking about your own sales numbers or commiserating about the demands of the job and, just like that, your stress response is activated. The process then repeats with everyone you interact with—and snowballs from there.

“It’s a vicious cycle: The more stressed we are, the more likely we are to stress out others around us, increasing stress contagion and creating an overall more stressful environment for everyone,” says Dan Keating, author of Born Anxious: The Lifelong Impact of Early Life Adversity—and How to Break the Cycle.

The key is to boost your stress immunity so you can filter out others’ stress when it’s not serving you. Here’s how to protect yourself against secondary stress—and avoid contributing to the cycle yourself:

1. Change Your Response
Your reaction dictates whether or not you internalize others’ stress. First, try not to take it personally—people who cause secondhand stress are usually unaware of the impact they’re having on others, explains Heidi Hanna, Executive Director for the American Institute of Stress. Instead of joining in or getting frustrated when you witness secondhand stress, think of it as a chance to practice empathy, spread compassion, or help that person work through a challenge.

2. Be a Positive Influence
Positive emotions spread just like stress—so if you cultivate an upbeat energy, others will feel it, too. Here are some simple ways to do just that:

• Express gratitude: This activates the body’s “feel good” hormones and leads to a positive emotional state for both the giver and receiver.
• Be a role model: Respond to tense or closed-off body language with a smile or a nod of understanding.
• Up your positivity ratio: For every lousy thing that happens at work, name two things that are going well.
• Celebrate your wins: When something good happens—even if it’s small—share it one-on-one with someone who would appreciate it.

3. Stop Secondhand Stress Before it Spreads
Sometimes the best way to neutralize transmitted stress is to address it directly. Help the other person return to calm by encouraging them to take a deep breath, which activates the parasympathetic nervous system, balances out the sympathetic nervous system, and works to calm us down.

Then, ask them to verbalize what they’re feeling. Naming our worries can bring some much-needed clarity. Validate their experience (“That sounds difficult. I’m sorry you’re dealing with this.”) and then remind them of their own skills and abilities with a compliment: “You really showed great leadership in the meeting when we talked about budget limitations.” Before the conversation turns negative, offer your continued support and direct the conversation away from the emotional high stress (“I know you’re good at what you do and I’m here to give you a pep talk next time you need.”) Then, excuse yourself and head to the breakroom, take a stroll outside, or return to your desk to avoid getting pulled into the stress cycle.

Polly Campbell is a veteran author and speaker specializing in psychology, resilience, and wellness topics for more than 20 years. She is the author of three books: How to Live an Awesome Life: How to Live Well. Do Good. Be Happy; Imperfect Spirituality: Extraordinary Enlightenment for Ordinary People; and How to Reach Enlightenment. Tweet her @PLCampbell.