We often think of contagious diseases as being caused by viruses, bacteria, or parasites. When someone we know gets sick with a cold, the flu, or something else, we tend to keep our distance. However, there are many other things that can be passed from person to person that you might not even realize. Some of these are quite surprising, going far beyond the typical illnesses. Get ready to find out about some unexpected things you can ‘catch’ from others—no hand sanitizer can help you with these!
10. Heart Disease
Heart disease is often thought to be caused by genetics and lifestyle. However, recent research suggests it can also be contagious. Scientists have discovered that heart disease, along with conditions like IBS and type 2 diabetes, can spread through altered microbiomes—the mix of bacteria, fungi, and parasites in our gut.
When these unhealthy microbiomes are transferred to animal models, they cause disease in the new host, much like a stomach bug. Research is ongoing to determine if healthy microbiomes can also be passed from one person to another.
9. Loneliness
It might seem strange, but loneliness can be contagious. A long-term study involving over 5,000 people and their social connections showed that loneliness can spread from person to person. People often start feeling lonely before they become completely isolated.
This means they’re still interacting with friends and family, unintentionally sharing their feelings of loneliness. These feelings can then take root in others, creating a cycle of loneliness. Interestingly, you’re more likely to catch loneliness from friends than family, and women are generally more susceptible than men.
8. Ulcers
For a long time, stress and spicy foods were blamed for causing peptic ulcers. However, the real culprit is a bacterium called Helicobacter pylori. Over half the world’s population is infected with this bacterium.
While some people with H. pylori never experience symptoms, others develop peptic ulcers in the stomach and small intestine. This bacterium spreads through saliva and fecal matter, so sharing saliva and not washing hands properly can increase your risk of developing an ulcer.
7. Feeling Cold
Believe it or not, you can catch the feeling of being cold. Researchers at the University of Sussex found that people can experience temperature contagion, where watching someone in a cold situation can actually lower your own body temperature.
In a study, participants watched a video of someone putting their hand in ice water. Viewers not only said they felt colder, but their hand temperature also decreased. Interestingly, this effect was only observed with coldness, not warmth.
6. Happiness
We all know that being around happy people tends to lift our spirits, while being around negative people can bring us down. It turns out that happiness is influenced by more than just our immediate circle of friends and family.
The mood of your neighbors can significantly affect your own happiness. Studies show that having a cheerful sibling nearby can increase your odds of happiness by 14%, while a happy next-door neighbor can increase them by 34%. A happy friend living close by can boost your happiness by over 40%.
5. Cancer
While it’s rare, cancer can be contagious in certain situations. There are currently three animals that can transmit cancer: Tasmanian devils (through bites), dogs (through sexual contact), and soft-shelled clams (through seawater).
In humans, there have been rare cases of cancer spreading through organ transplants from donors with undiagnosed cancer. However, these cases typically involve individuals with compromised immune systems. Contagious cancer is highly unlikely in humans outside of these unusual circumstances.
4. Bad Behavior
Being around people who break the rules can influence us to do the same. Research shows that exposure to rule-breaking behavior can make us more likely to break rules ourselves, even in different situations.
For instance, if you see others littering, you might be more likely to litter as well. This exposure to breaking social norms can also lead to other bad behaviors, such as stealing snacks from the office or not cleaning up after your pet.
3. High Blood Pressure
High blood pressure, usually linked to poor diet and lifestyle, has also been connected to a common contagious virus. Researchers found that mice infected with cytomegalovirus (CMV) developed higher blood pressure than those without the virus.
Mice with CMV that also ate high-cholesterol foods had the highest blood pressure rates. Human cells infected with CMV produce a protein that contributes to high blood pressure. CMV affects a large percentage of adults worldwide and is transmitted through bodily fluids, staying in the body for life.
2. Goals
We can unintentionally adopt the goals of people we interact with through a phenomenon called goal contagion. We often subconsciously pick up on others’ goals through their behavior, body language, and conversation topics.
If someone is trying to relax and enjoy themselves, we’ll likely adopt that goal as well. Conversely, if someone is eager to leave an event early, we might find ourselves feeling the same way. Goal contagion is stronger with people in our inner circle and less likely when the goal is seen as inappropriate.
1. Cavities
Cavities are caused by bacteria in our mouths that convert sugar into acid, which eats away at the tooth enamel. Even with regular brushing and flossing, kissing someone with poor dental hygiene can introduce cavity-causing bacteria into your mouth.
Children are particularly vulnerable because they haven’t built up immunity to these bacteria. Adults can pass these bacteria to children by kissing them, sharing utensils, or cleaning pacifiers with their mouths.
