Infectious diseases are caused by microorganisms such as viruses, bacteria, fungi or parasites and can spread between individuals.
What is an infectious disease?
- Infectious diseases are caused by microorganisms such as viruses?, bacteria?, fungi or parasites?.
- Microorganisms that cause disease are collectively called pathogens.
- 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.
- 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.
- Infectious diseases are one of the leading causes of death worldwide.
- Many diseases become difficult to control if the infectious agents evolve resistance to commonly used drugs:
Scientists are currently searching for new approaches to treat infectious disease, focusing on exactly how the pathogens change and drug resistance evolves.
What causes an infectious disease?
- Viruses are tiny infectious agents that replicate only in the living cells of other organisms.
- They have a very simple structure consisting of genetic material in the form of DNA or RNA within a protein capsule.
- They can infect all types of life forms, from animals to plants and bacteria to amoebae.
- Viruses can be spread in many ways including:
- From plant to plant by insects that feed on plant sap. For example, Potato virus Y which is spread by aphids.
- From animal to animal by blood-sucking insects. For example, Dengue virus which is spread by mosquitos.
- Spread by aerosols (through coughing and sneezing). For example, influenza virus.
- Spread by not washing hands after going to the toilet. For example, norovirus or rotavirus.
- Spread by sexual contact. For example, HIV and Human Papillomavirus (HPV).
- Spread by exposure to infected blood. For example, Hepatitis B.
- Viruses can often be prevented through vaccines.
- Bacteria are single-celled microorganisms.
- They come in many shapes including ball-, rod- and spiral-shaped.
- Most bacteria are not harmful and some are actually beneficial. Less than one per cent of bacteria will actually make you ill.
- Infectious bacteria can grow, divide and spread in the body, leading to infectious disease.
- Some infectious bacteria give off toxins which can make some diseases more severe.
- Bacteria are spread in many ways including:
- Spread by aerosols (through coughing and sneezing). For example, Streptococcus.
- Spread by surface and skin contact. For example, Staphylococcus aureus, including MRSA.
- Spread through body fluids, such as blood and saliva. For example, meningococcal disease (meningitis).
- Antibiotics are usually given to treat severe bacterial infections.
- Antibiotic resistance in bacteria is a significant problem.