Ringworm: reddish, itchy, scaly rash usually on the skin and scalp.Athlete’s foot: itching, scaling or cracking of the skin.Some infections may also penetrate the body to affect organs and cause whole-body infections. Fungal infections often affect the lungs, skin or nails.Fungi reproduce by releasing spores that can be picked up by direct contact or even inhaled.Other fungi can be infectious and may lead to life-threatening diseases.Most fungi are harmless to humans and some are edible.Fungi are microorganisms characterised by cell walls made from a substance called chitin.Antibiotic resistance in bacteria is a significant problem.Antibiotics are usually given to treat severe bacterial infections.For example, meningococcal disease (meningitis). Spread through body fluids, such as blood and saliva.For example, Staphylococcus aureus, including MRSA. Spread by aerosols (through coughing and sneezing).Bacteria are spread in many ways including:.Some infectious bacteria give off toxins which can make some diseases more severe.Infectious bacteria can grow, divide and spread in the body, leading to infectious disease.Less than one per cent of bacteria will actually make you ill. Most bacteria are not harmful and some are actually beneficial.They come in many shapes including ball-, rod- and spiral-shaped.Bacteria are single-celled microorganisms.Image credit: Ben Taylor, via Wikipedia commons Viruses can often be prevented through vaccines.For example, HIV and Human Papillomavirus (HPV). Spread by not washing hands after going to the toilet.For example, influenza virus or the novel coronavirus SARS-CoV-2. For example, Dengue virus which is spread by mosquitos. From animal to animal by blood-sucking insects.For example, Potato virus Y which is spread by aphids. From plant to plant by insects that feed on plant sap.Viruses can be spread in many ways including:.They can infect all types of life forms, from animals to plants and bacteria to amoebae.Viruses have a very simple structure consisting of genetic material in the form of DNA or RNA within a protein capsule.Viruses are tiny infectious agents that replicate only in the living cells of other organisms.Scientists are currently searching for new approaches to treat infectious diseases, focusing on exactly how the pathogens change and drug resistance evolves.
For example, bacteria can accumulate mutations in their DNA or acquire new genes that allow them to survive contact with antibiotic drugs that would normally kill them.Many diseases become difficult to control if the infectious agents evolve resistance to commonly used drugs:.Infectious diseases are one of the leading causes of death worldwide.Infectious diseases can be spread from one person to another, for example through contact with bodily fluids, by aerosols (through coughing and sneezing), or via a vector, for example a mosquito.Ĭlose up of a mosquito feeding on human blood.Pathogens cause disease either by disrupting the bodies normal processes and/or stimulating the immune system to produce a defensive response, resulting in high fever, inflammation and other symptoms.Microorganisms that cause disease are collectively called pathogens.Infectious diseases are caused by microorganisms such as viruses, bacteria, fungi or parasites.
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