Infections

An act or process of infecting is called infection. Infections are the most common cause of disease and they can take on a wide range of forms. Infections are caused by tiny living things (organisms) that get into our body and start multiplying. Some organisms are harmless and help our bodies to work properly. But others cause disease and the different types of organisms includes:

Bacteria are generally spread from an already infected person to the newly infected person. The most common invasion routes are inhalation of airborne bacteria, ingestion into the stomach from dirty hands or utensils, or through contaminated food or water, direct contact with an infected area of another person's body, contaminated blood, or by insect bite.

Viruses
Viruses are tiny particles that can't live on their own. To reproduce, they need to infect a living cell, such as a cell in a human body. It is a virus that causes flu. Viruses usually infect one particular type of cell. For example, cold viruses infect only cells of the upper respiratory tract. Additionally, most viruses infect only a few species of plants or animals; some infect only people. Viruses are transmitted in a variety of ways. Some are swallowed, some are inhaled, and some are transmitted by the bites of insects and other parasites (for example, mosquitoes and ticks).

Probably the most common viral infections are those of the nose, throat, and airways. These infections include sore throat, sinusitis, the common cold, and influenza. Doctors often refer to these as upper respiratory infections (URIs). In small children, viruses also commonly cause croup and inflammation of the windpipe (laryngitis) or other airways deeper inside the lungs (bronchiolitis, bronchitis.)

Fungal infections
Fungi can live in our bodies without causing any problems. But if a fungal infection occurs when your immune system is weak, it can cause problems. The most common fungal infections are:

Tinea which is a type of fungal infection of the hair, skin, or nails. When it's on the skin, tinea usually begins as a small red area the size of a pea. As it grows, it spreads out in a circle or ring. Tinea is often called ringworm because it may look like tiny worms are under the skin. Because the fungi that cause tinea (ringworm) live on different parts of the body, they are named for the part of the body they infect. Scalp ringworm is found on the head, and body ringworm affects the arms, legs, or chest.

Athlete's foot is another type of fungal infection that usually appears between the toes but can also affect toenails and the bottom or sides of the feet.

Jock itch is a fungal infection of the groin and upper thighs. You might think only men and boys get it, but girls and women can get it, too.

Candida is a yeast, similar to a fungus. It most often affects the skin around the nails or the soft, moist areas around body openings. Diaper rash in babies is one type of candidal infection, as is thrush (white patches often found in the mouths of babies.) Older girls and women may develop another form of candidal infection in and around the vagina. This is called a yeast infection.

Protozoal infections Protozoa are microscopic organisms that consist of a single cell, but are larger than bacteria. Free-living protozoa, like amoebas, are found in ponds and rivers and rarely cause disease in animals and humans. Two kinds of protozoan parasites, giardia and coccidia, have the potential to cause disease, and occur in animals nearly as commonly as the intestinal worms.

Giardiasis is contracted by ingestion of feces or contact with an environment or body of water contaminated with feces from an animal with the disease. Signs, if they occur, may show up in as little as 5-7 days, but the organism may not be detected in a stool sample for several weeks.

Coccidiosis, on the other hand, is more species specific, so that each species of coccidia usually cause disease in only one species of animal. Similar to giardia, infection is usually achieved by a fecal-oral route. However, coccidia have the potential to form cysts in the host animal’s intestines and other organs, sometimes animals of different species. This means that small mammals, including rabbits, may act as carriers of canine coccidia. As with giardia, coccidia infection can exist with no clinical signs.