Contagious
adjective
Definition
1. Able to spread from one person to another through direct or indirect contact.
2. Describing a disease or illness that can be transmitted.
3. Spreading easily from person to person, especially emotions, behaviors, or attitudes.
2. Describing a disease or illness that can be transmitted.
3. Spreading easily from person to person, especially emotions, behaviors, or attitudes.
Context Alive
The doctor stepped back from the examination and removed her gloves carefully. The child’s symptoms were unmistakable, and she needed to act quickly. She explained to the worried parents that the infection was highly contagious and that their son would need to stay home from school for at least a week, avoiding contact with his younger siblings to prevent the illness from spreading through the entire household.
Meanings
5 meanings
1
Able to spread disease from person to person (Adjective) — VERY COMMON
Common
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This is the most common and literal meaning of the word. When an illness is contagious, it can pass from a sick person to a healthy person through touch, air, or shared objects. Think about catching a cold from a coworker who kept sneezing in the office — the virus was contagious, jumping from person to person until half the team was sick and working from home with tissues and tea. Or imagine a parent keeping their child home from school because the flu going around is extremely contagious, and one sick kid in a classroom can infect twenty others within days. The word makes you think about distance, hand-washing, and staying away from people who are unwell.
Vivid ExampleThe nurse warned that the patient was still contagious and would need to remain in isolation for another forty-eight hours, with visitors required to wear masks and gloves before entering the room.
2
Describing emotions that spread easily to others (Adjective) — VERY COMMON
Common
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This is an equally common but figurative use of the word. Emotions like laughter, enthusiasm, or even fear can be contagious, spreading through a group almost like a virus. You know when someone starts laughing uncontrollably and suddenly everyone around them is laughing too, even if they don’t know what’s funny? That laughter is contagious, passing from person to person until the whole room is infected with giggles. Or think about a nervous feeling spreading through a crowd waiting for exam results — one person starts pacing anxiously, and soon that anxiety becomes contagious, with everyone fidgeting and checking their phones obsessively.
Vivid ExampleHer excitement about the trip was absolutely contagious, and within minutes her whole family had caught her enthusiasm, rushing to pack bags and make plans they hadn’t even considered an hour earlier.
3
Describing behaviors or attitudes that spread through groups (Adjective) — COMMON
Common
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Beyond emotions, contagious can describe behaviors, attitudes, or ideas that spread from person to person in social settings. Picture a workplace where one employee starts arriving late, and soon that careless attitude becomes contagious, with more and more people drifting in after the official start time because nobody seems to care anymore. Or imagine a positive example — a new team leader brings incredible energy and dedication, and that work ethic proves contagious, inspiring everyone around her to raise their own standards. Whether good or bad, behaviors can infect groups just like diseases do.
Vivid ExampleThe captain’s calm confidence under pressure was contagious, spreading through the nervous team until every player walked onto the field believing they could win against the heavily favored opponents.
4
Describing a smile or expression that makes others react similarly (Adjective) — COMMON
Common
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You’ll often hear people describe someone’s smile or energy as contagious, meaning it naturally makes others smile or feel the same way. Think about meeting someone with such a warm, genuine smile that you can’t help but smile back — their expression is contagious, lifting your mood without them saying a single word. Or imagine a baby laughing in a grocery store, and suddenly strangers are stopping, grinning, and laughing along because that pure joy is so contagious that even tired adults can’t resist catching it. This usage is almost always positive, describing people who brighten every room they enter.
Vivid ExampleThe little girl had the most contagious giggle anyone had ever heard, and within seconds of her laughing at the playground, children and parents alike were chuckling without even knowing what was so funny.
5
Likely to spread rapidly or widely (Adjective) — LESS COMMON
Common
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In broader contexts, contagious describes anything that spreads quickly and widely, including ideas, trends, or information. Imagine a video going viral on social media — something about it is contagious, making people feel compelled to share it with everyone they know until millions have watched. Or think about how rumors in a small town can be dangerously contagious, starting with one whispered conversation and spreading house to house until everyone believes something that may not even be true. This meaning emphasizes the speed and ease of spread rather than the personal contact of the medical meaning.
Vivid ExampleThe conspiracy theory proved frighteningly contagious on social media, spreading from a single post to millions of believers within weeks despite fact-checkers repeatedly debunking its claims.
Examples from the Street
“Stay home if you’re sick — you might be contagious.”
Don’t come in if you’re unwell — you could pass it on to others
“Her laughter is so contagious — everyone starts giggling when she does.”
Her amusement spreads to everyone around her; you can’t help but join in
“Fear can be contagious — one person panics and suddenly everyone does.”
Anxiety spreads quickly through a group; one scared person triggers others
Common Patterns
be contagious → able to spread to others through contact
highly/extremely contagious → spreading very easily from person to person
contagious disease/illness/virus → a sickness that spreads between people
still contagious → still able to infect others
no longer contagious → no longer able to spread the illness
contagious laughter/smile → amusement that spreads to others
contagious enthusiasm/energy → excitement that infects those around you
contagious fear/panic → anxiety that spreads quickly through a group
something is contagious → an emotion or behaviour spreads easily
positivity/negativity is contagious → good or bad attitudes affect others
Collocations
4 collocationshighly contagious
spreading very easily from person to person
contagious laughter
laughter that makes others laugh too
contagious enthusiasm
excitement that spreads to those around you
contagious disease
an illness that passes easily between people
Example Sentences
12 examples
1
The doctor said I’m still contagious and should stay home for another few days
The physician told me I can still pass on the illness and must remain indoors a bit longer.
2
Covid-19 proved to be highly contagious, spreading rapidly across the globe
The virus turned out to transmit extremely easily, moving quickly around the world.
3
Children with chickenpox are contagious until all the spots have crusted over
Young ones with that spotty illness can infect others until every mark has dried up.
4
Once the fever breaks, you’re usually no longer contagious
After your high temperature goes down, you typically can’t spread the sickness anymore.
5
She has such a contagious laugh — you can’t help but smile when you hear it
Her giggles are so infectious — it’s impossible not to grin when she starts.
6
His contagious enthusiasm for the project motivated the entire team
His excitement about the work spread to everyone and inspired the whole group.
7
Yawning is contagious — if one person yawns, others usually follow
Opening your mouth widely in tiredness spreads easily — when someone does it, the rest tend to copy.
8
In a crisis, panic is contagious — that’s why leaders must stay calm
During emergencies, fear spreads rapidly — that’s why those in charge must remain composed.
9
A positive attitude can be just as contagious as a negative one
An optimistic outlook can spread to others just as easily as a pessimistic one.
10
Her passion for music was contagious — she made everyone want to learn an instrument
Her love of playing tunes spread to those around her — she inspired everyone to pick up something to play.
Learner Examples
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A teacher’s enthusiasm for the subject is contagious — if you’re excited about English, your students will be too
An instructor’s passion for what they teach spreads easily — if you love the language, your learners will catch that feeling.
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Unfortunately, boredom in the classroom can also be contagious — one distracted student can affect the whole group
Sadly, lack of interest during lessons spreads quickly too — a single unfocused learner can influence everyone else.
Phrasal Verbs & Idioms
1 items Idioms & Expressionslaughter is contagious — laughter spreads to others easily
Her giggles proved that laughter is truly contagious.
Synonyms & Antonyms
6 items
Synonymsinfectious
spreading easily to others
catching
informal, easy to catch
spreadable
able to pass from person to person
transmissible
medical, can be transmitted
Antonymsnon-contagious
cannot be spread
harmless
not dangerous to others