Infection happens when germs (small living things) invade and grow in a person’s body. Those germs can be bacteria, viruses, fungi or parasites. When people get infections, their immune systems try to stop the organisms from harming them. If the infection is serious, illness or death can result.
Most organisms that cause infections are too small to see with the naked eye. They live in and on the body in many different places, including the mouth, nose and eyes, and in the bowels. Normally, they’re harmless or even helpful. But under certain conditions, these microorganisms can become pathogens and make you sick.
There are trillions of bacteria in and on us, and most don’t cause sickness. But if too many bacteria are present, they can overgrow and create an imbalance with other types of bacteria that keep you healthy. This overgrowth can then lead to disease. Bacterial diseases include skin infections (abrasions, blisters and ulcers), digestive tract infections like diarrhea and vomiting, and lung infections such as bronchitis and pneumonia.
Other types of infection include viral infections, fungi and protozoal infections. Viruses, fungi and protozoa all have the potential to make you very sick or possibly die. Viral infections happen when tiny particles called viruses infiltrate cells, either killing the cell or turning its cellular machinery over to produce more virus particles. Fungi have a similar life cycle. Parasites are larger multi-celled organisms that live inside other cells or outside the cell. They often spread through blood, saliva or urine, and they can also be carried by fleas, mites, ticks, rats and snails.
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