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. Spores are harder to kill than active bacteria because of their outer coating. 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. Antibodies produced by the immune system attach to the bacteria and help in their destruction.
They may also inactivate toxins produced by particular pathogens, for example tetanus and diphtheria. Immunisation is available to prevent many important bacterial diseases such as Hemophilus influenza Type b Hib , tetanus and whooping cough.. A virus is a miniscule pocket of protein that contains genetic material. If you placed a virus next to a bacterium, the virus would be dwarfed. For example, the polio virus is around 50 times smaller than a Streptococci bacterium, which itself is only 0.
The four main types of virus include:. This makes it difficult for antibodies to reach them. Some special immune system cells, called T-lymphocytes, can recognise and kill cells containing viruses, since the surface of infected cells is changed when the virus begins to multiply.
Many viruses, when released from infected cells, will be effectively knocked out by antibodies that have been produced in response to infection or previous immunisation. Antibiotics are useless against viral infections.
This is because viruses are so simple that they use their host cells to perform their activities for them. So antiviral drugs work differently to antibiotics, by interfering with the viral enzymes instead. Antiviral drugs are currently only effective against a few viral diseases, such as influenza, herpes, hepatitis B and C and HIV — but research is ongoing. A naturally occurring protein, called interferon which the body produces to help fight viral infections , can now be produced in the laboratory and is used to treat hepatitis C infections.
It is possible to vaccinate against many serious viral infections such as measles, mumps, hepatitis A and hepatitis B. An aggressive worldwide vaccination campaign, headed by the World Health Organization WHO , managed to wipe out smallpox. However, some viruses — such as those that cause the common cold — are capable of mutating from one person to the next.
This is how an infection with essentially the same virus can keep dodging the immune system. Vaccination for these kinds of viruses is difficult, because the viruses have already changed their format by the time vaccines are developed. Examples of bacteria that cause infections include Streptococcus , Staphylococcus , and E.
Antibiotics are the usual treatment. When you take antibiotics, follow the directions carefully. Each time you take antibiotics, you increase the chances that bacteria in your body will learn to resist them causing antibiotic resistance.
Later, you could get or spread an infection that those antibiotics cannot cure. The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health. Bacterial Infections. Homepage Why Microbiology Matters What is microbiology?
Microbes and the human body Microbes and disease. An infection is the invasion and multiplication of pathogenic microbes in an individual or population. An infection does not always result in disease! Microbes can enter the body through the four sites listed below: Respiratory tract mouth and nose e.
Gastrointestinal tract mouth oral cavity e.
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