Vibrio cholerae which causes cholera. Urogenital tract e. Escherichia coli which causes cystitis. Breaks in the skin surface e.
Clostridium tetani which causes tetanus. Immune system An infection can be seen as a battle between the invading pathogens and host. Routes of transmission Find out how you can pick up germs and pass them on to others.
Vaccination Just a shot in the arm — what do vaccines do? Infections — bacterial and viral. Actions for this page Listen Print. Summary Read the full fact sheet. On this page. How bacteria and viruses enter the body To cause disease, pathogenic bacteria must gain access into the body. The range of access routes for bacteria includes: Cuts Contaminated food or water Close contact with an infected person Contact with the faeces of an infected person Breathing in the exhaled droplets when an infected person coughs or sneezes Indirectly, by touching contaminated surfaces — such as taps, toilet handles, toys and nappies.
Viruses are spread from one person to another by: Coughs Sneezes Vomits Bites from infected animals or insects Exposure to infected bodily fluids through activities such as sexual intercourse or sharing hypodermic needles. Bacteria types Bacteria that cause disease are broadly classified according to their shape. The four main groups include: Bacilli — shaped like a rod with a length of around 0.
Illnesses such as typhoid and cystitis are caused by bacilli strains. Cocci — shaped like a sphere with a diameter of around 0. Depending on the sort, cocci bacteria group themselves in a range of ways, such as in pairs, long lines or tight clusters.
Examples include Staphylococci which cause a host of infections including boils and Gonococci which cause the sexually transmissible infection gonorrhoea. Spirochaetes — as the name suggests, these bacteria are shaped like tiny spirals. Spirochaetes bacteria are responsible for a range of diseases, including the sexually transmissible infection syphilis. Vibrio — shaped like a comma. The tropical disease cholera, characterised by severe diarrhoea and dehydration, is caused by the vibrio bacteria.
Characteristics of the bacterium Most bacteria, apart from the cocci variety, move around with the aid of small lashing tails flagella or by whipping their bodies from side to side. Curing a bacterial infection The body reacts to disease-causing bacteria by increasing local blood flow inflammation and sending in cells from the immune system to attack and destroy the bacteria.
Virus types A virus is a miniscule pocket of protein that contains genetic material. The four main types of virus include: Icosahedral — the outer shell capsid is made from 20 flat sides, which gives a spherical shape. Most viruses are icosahedral.
Helical — the capsid is shaped like a rod. Enveloped — the capsid is encased in a baggy membrane, which can change shape but often appears spherical. Complex — the genetic material is coated, but without a capsid. Curing a viral infection Antibiotics are useless against viral infections. Immunisation against viral infection is not always possible It is possible to vaccinate against many serious viral infections such as measles, mumps, hepatitis A and hepatitis B.
Where to get help Your doctor Your pharmacist Things to remember Many human illnesses are caused by infection with either bacteria or viruses. Most bacterial diseases can be treated with antibiotics, although antibiotic-resistant strains are starting to emerge. It is possible to be vaccinated against some of the major disease-causing viruses such as measles and polio , as well as bacterial diseases such as Hemophilus influenza Type b Hib , tetanus and whooping cough.
For instance, Lactobacillus acidophilus — a harmless bacterium that resides in your intestines — helps you digest food, destroys some disease-causing organisms and provides nutrients. Many disease-causing bacteria produce toxins — powerful chemicals that damage cells and make you ill.
Other bacteria can directly invade and damage tissues. Some infections caused by bacteria include:. Viruses are much smaller than cells. In fact, viruses are basically just capsules that contain genetic material. To reproduce, viruses invade cells in your body, hijacking the machinery that makes cells work.
Host cells are often eventually destroyed during this process. There are many varieties of fungi, and we eat several of them. Mushrooms are fungi, as are the molds that form the blue or green veins in some types of cheese.
And yeast, another type of fungus, is a necessary ingredient in most types of bread. Other fungi can cause illness. One example is candida — a yeast that can cause infection. Candida can cause thrush — an infection of the mouth and throat — in infants and in people taking antibiotics or who have an impaired immune system.
Fungi are also responsible for skin conditions such as athlete's foot and ringworm. Protozoans are single-celled organisms that behave like tiny animals — hunting and gathering other microbes for food. Many protozoans call your intestinal tract home and are harmless. Others cause diseases, such as:. Protozoans often spend part of their life cycles outside of humans or other hosts, living in food, soil, water or insects. Some protozoans invade your body through the food you eat or the water you drink.
Others, such as malaria, are spread by mosquitoes. Helminths are among the larger parasites. The word "helminth" comes from the Greek word for worm. If these parasites — or their eggs — enter your body, they take up residence in your intestinal tract, lungs, liver, skin or brain, where they live off your body's nutrients.
Helminths include tapeworms and roundworms. There's a difference between infection and disease. Infection, often the first step, occurs when bacteria, viruses or other microbes that cause disease enter your body and begin to multiply. Disease occurs when the cells in your body are damaged — as a result of the infection — and signs and symptoms of an illness appear. In response to infection, your immune system springs into action.
An army of white blood cells, antibodies and other mechanisms goes to work to rid your body of whatever is causing the infection. For instance, in fighting off the common cold, your body might react with fever, coughing and sneezing. What's the best way to stay disease-free?
Prevent infections. You can prevent infections through simple tactics, such as washing your hands regularly, avoiding close contact with people who are sick, cleaning surfaces that are touched often, avoiding contaminated food and water, getting vaccinations, and taking appropriate medications. Your doctor can perform diagnostic tests to find out if you're infected, the seriousness of the infection and how best to treat that infection.
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