Bacteria are tiny organisms (living things) that have only one cell. Under a microscope, they look like balls, rods, or spirals. They can be found almost everywhere on Earth. There are lots of bacteria in and on your body. In fact, your body has about 10 times more bacteria cells than human cells.

There are many different types of bacteria. Most types don't make you sick. Some types are helpful. For example, "good" bacteria in your digestive system can help your body digest food and absorb vitamins and minerals. They can help protect you from getting sick. Bacteria are also used in making foods like yogurt and cheese.

But some types of bacteria can cause an infection and make you sick. They are called infectious bacteria. These bacteria can reproduce quickly in your body. Many of them give off toxins (poisons) that can damage your cells and make you sick. Other types can move into and damage your tissues. A few examples of bacteria that cause infections include Streptococcus, Staphylococcus, and E. coli.

There are different ways that bacterial infections may spread:

• Through droplets and particles that are breathed out by someone who has the infection. You might breathe in the droplets or particles, or they could land on your mouth, nose, or eyes.
• By touching surfaces or objects that have the bacteria on them and then touching your mouth, nose, or eyes.
• Through cuts, scrapes, and skin-to-skin contact with someone who has the infection.
• From the pregnant parent to the baby during pregnancy.
• Through contaminated food or water.
• By being bitten by an infected insect or animal.
• Through sexual contact (usually vaginal, anal and oral sex) with someone who has the infection.

Sometimes your immune system may be able to fight off a bacterial infection. But when you do need treatment, it will be with antibiotics.

You can help prevent some bacterial infections by:

• Getting vaccines that protect against bacterial infections.
• Having good hygiene habits. These include washing your hands often and covering your mouth and nose when coughing or sneezing.
• Paying attention to food safety.
• Cleaning and disinfecting surfaces that your frequently touch.
• Preventing insect bites by using a U.S. Environmental Protection Agency (EPA)-registered insect repellent. when you go outdoors. If you travel to an area that has a high risk of diseases from insect bites, also wear long pants, shirts, and socks.
• Practicing safe sex. This means using a latex condom every time you have anal, vaginal, or oral sex. If your or your partner is allergic to latex, you can use polyurethane condoms.
• Avoiding close contact with people who are sick.