Medically Reviewed by Carol DerSarkissian, MD on October 21, 2020

Contagious or Not?

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Some germs are contagious. That means they spread from person to person. But there are many types of infections you won’t get from another person. You might pick up germs by touching surfaces, or by eating or drinking things that have bacteria or viruses in them. Some diseases spread only through infected insects or other animals. Sometimes, microbes that live in or on your body can start to grow out of control and cause an infection.

Legionnaires Disease

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It’s a type of pneumonia that you get when you breathe in droplets of water or accidentally inhale water that has Legionella bacteria. Legionella live in lakes and streams. But people can become infected if the bacteria make their way into water systems and start to grow there, such as in shower heads, sink faucets, hot tubs, water heaters, or pipes.

Ear Infections

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They usually happen when an illness or allergies cause congestion in your nose, throat, and Eustachian tubes, which run from each ear to the back of the throat. The fluid that builds up in your middle ear allows germs to grow. While contagious cold and flu bugs sometimes lead to an ear infection, you can’t catch one from someone else.

Urinary Tract Infection

4/13

A UTI starts when bacteria from the rectum or somewhere else on the skin get into the urinary tract through the urethra. Women get UTIs more often than men mainly because their urethra is closer to the rectum. Some people get these infections after sex, when bacteria from a partner make their way into the urethra. You can help prevent this by peeing right after sex. But you don’t have to have sex to get this type of infection.

Vaginal Yeast Infection

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It happens when the normal balance of microbes, including yeast and bacteria, in your vagina is thrown off. That means yeast can start to grow too much, causing itching, burning, and irritation. You might be more likely to get them if you’re taking antibiotics, you’re pregnant, you have uncontrolled diabetes, or a weakened immune system. Some birth control pills can cause them too. You can’t give a yeast infection to another person.

Sinus Infection (Sinusitis)

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Like an ear infection, sinus infections happen when mucus builds up in your sinuses and germs start to grow there. The common cold, which is a viral infection, is most often the cause of sinus infections. Sometimes, a bacterial infection is behind sinusitis.  If a virus is the cause, the infection is contagious. But, it’s more likely you’ll spread the cold than the sinus infection itself

Salmonella

7/13

This type of bacteria can cause an infection in your intestines. If you eat raw or undercooked food containing salmonella bacteria -- often meat, eggs, or poultry -- you can get a salmonella infection. Salmonella can end up on countertops and kitchen gadgets and then contaminate other food. Thorough cooking kills this bacteria. Symptoms of salmonella infection can include nausea, vomiting, diarrhea, cramps, fever, chills, and headache. 

E. coli

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It’s normal to have this type of bacteria in your intestines. But some strains of E. coli make people sick. People usually get them by eating food or drinking water that has the bacteria. It’s more common with raw vegetables or undercooked ground beef. The infection can cause severe, bloody diarrhea, nausea, vomiting, and stomach cramps.

Naegleria fowleri

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You might have heard it called a brain-eating amoeba. Naegleria fowleri causes a rare deadly brain infection. This tiny organism, or amoeba, gets into your brain through your nose. It lives in warm lakes or rivers,  or naturally hot water. Swimming pools without enough chlorine can host them too. The infection, which causes seizures, confusion, and hallucination, can kill people in as little as 5 days.

Rabies

10/13

You get rabies when an animal that carries the virus  bites you. Most cases involve infected bats, coyotes, dogs, and cats. Rabies is deadly, but it’s rare for people to get it. If you are bit or scratched by an animal that might have rabies, a doctor can give you a vaccine to protect you from the virus.

Infections From Ticks

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Ticks can pass many different bacteria and viruses to people through a bite. Some bacterial infections that ticks carry include Lyme disease and Rocky Mountain spotted fever. Some well-known viruses are Colorado tick fever and Bourbon virus. If a tick burrows into your skin, remove it with tweezers, not a lit match. If possible, seal the tick in a container and freeze it. If you get sick in the next few days, see a doctor. If possible, bring the tick. 

Infections From Mosquitoes

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Mosquitoes carrying viruses, including malaria, Zika, West Nile, yellow fever, dengue fever, and chikungunya, can pass them to people through a bite. These infections tend to happen in specific parts of the world. 

Infections From Rodents

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These usually happen when people are in contact with waste from infected rats, mice, or other rodents. You can also breathe dust that’s carrying specks of rodent droppings or urine. You can get hantavirus, hemorrhagic fever, and other illnesses. If you need to clean up droppings, don’t stir up dust with a broom or vacuum cleaner. Put on gloves, spray the area with disinfectant, and wipe it clean. Then take care of the rodent that left the droppings. 

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SOURCES:

Mayo Clinic: “Infectious Diseases,” “Ear Infections,” “Urinary Tract Infections,” “Yeast Infection,” “Salmonella,” “E. coli,” “Rabies.”

Harvard Women’s Health Watch: “When urinary tract infections keep coming back.”

CDC: “Legionella,” “Sinus Infection (Sinusitis)”, “Naegleria fowleri,” “Ticks,” “Mosquito-Borne Diseases,” “Rodents.”

Planned Parenthood: “Urinary Tract Infections (UTIs).”

Tufts Medical Center: “Are Sinus Infections Contagious?”

University of Rochester Medical Center: “In the Kitchen: Prevent the Spread of Infection.”