Germs, or microbes, are found everywhere - in the air, soil, and water. There are also germs on your skin and in your body. Many of them are harmless, and some can even be helpful. But some of them can make you sick. Infectious diseases are diseases that are caused by germs.

There are four main types of germs:

• Bacteria are one-celled germs that multiply quickly. They may give off toxins, which are harmful chemicals that can make you sick. Strep throat and urinary tract infections are common bacterial infections.
• Viruses are tiny capsules that contain genetic material. They invade your cells so that they can multiply. This can kill, damage, or change the cells and make you sick. Viral infections include HIV and the common cold.
• Fungi are primitive plant-like organisms such as mushrooms, mold, mildew, and yeasts. Athlete's foot and yeast infections are common fungal infections.
• Parasites are animals or plants that survive by living on or in other living things. Malaria and head lice are infections that are caused by parasites.

There are many different ways that you can get an infectious disease, depending on the type of germ. They can include:

• Through direct contact with a person who is sick. This includes kissing, touching, sneezing, coughing, and sexual contact. Pregnant people can also pass some germs along to their babies.
• Through indirect contact, when you touch something that has germs on it. For example, you could get germs if someone who is sick touched a door handle, and then you touch it.
• Through insect or animal bites.
• Through contaminated food, water, soil, or plants.

Infectious diseases can cause many different symptoms. Some are so mild that you may not even notice any symptoms, while others can be life-threatening.

There are treatments for some infectious diseases, such as antibiotic, antiviral, antifungal and anti-parasitic medicines. But for other infections, such as some caused by viruses, you can only treat your symptoms while you wait for your immune system to fight off the germ.

You can take steps to help prevent many infectious diseases:

• Get vaccinated.
• Wash your hands often.
• Pay attention to food safety.
• Avoid contact with wild animals.
• Use a latex condom every time you have sex. If your or your partner is allergic to latex, you can use polyurethane condoms.
• Don't share items such as toothbrushes, combs, and straws.