Pathogenic A pathogenic organism causes disease or illness

Pathogenic A pathogenic organism causes disease or illness to its host by disrupting normal physiology BACTERIA V. cholerae M. tuberculosis VIRUSES smallpox flu TMV PROTOCTISTA P. falciparum

Infectious TRANSMITTED BY M NO NY SY ION breathing touching eating & drinking animal & insect bites kissing sexual contact T EN EV contagious communicable transmittable transmissible transferable conveyable spreading PR S Infectious diseases are transmitted to other people vaccines hand washing medicines

Disease reservoir Long term host of a pathogen, with few or no symptoms, which remains a potential source of disease outbreak. EXAMPLES Cholera in shellfish Rabies in bats Ebola in some primates Tapeworms in pigs Bird flu in ducks Carriers are infectious even though they do not have the symptoms of disease e. g. Typhoid Mary Vectors transmit disease e. g. malaria transmitted in a mosquito bite

Carrier A carrier is an infected person, or other organism, who shows no symptoms but can infect others. Typhoid Mary Herpes simplex virus can be transmitted before cold sores develop C. difficile can be transmitted e. g. in care homes by people with no symptoms HIV may have a long period of bring infectious, before symptoms appear

Endemic Disease occurring frequently, at a predictable rate, in a specific location or population. GENETIC US IO CT IN FE E RN BO Tay-Sachs disease occurs with higher frequency among Jews and French Canadians than other groups OD FO Chicken pox has a high, predictable rate in school children Liver fluke disease especially in east & southeast Asia, and central & south America

Epidemic The rapid spread of infectious disease to a large number of people within a short period of time, usually two weeks. Altered ecology allows new pathogen to make contact with population e. g. HIV in 1950 s Genetic change in pathogen allows it to increase its infectivity e. g. Spanish flu in 1918

Pandemic An epidemic over a very wide area, crossing international boundaries, usually affecting a large number of people. Characteristics: • infects humans • causes disease in humans • spreads between humans quite easily Mild: swine flu (2009) Serious: Polio (1950 s) Malaria 500 M deaths annually

Vaccine An antigenic substance prepared from a disease-causing organism, or a synthetic substitute, used to provide immunity against disease. Often made from: • weakened or killed microbe • its toxins • one of its surface proteins. Stimulates the body's immune system to: • recognize the agent as a threat • destroy it • keep a record of it Provides active acquired immunity to a particular disease

Antibiotics Substance produced by a microorganism that selectively kills or inhibits the growth of bacteria Antibiotics kill sensitive bacteria but mutant, resistant bacteria grow and multiply. Methicillin-resistant Staphylococcus aureus (MRSA) causes infections that are resistant to several common antibiotics. • Don't use antibiotics for virus infection • Finish the course: some bacteria may survive and cause re -infection

Antigen Any substance that causes your immune system to produce antibodies against it The body distinguishes “self” from “non-self”. “Non-self” molecules are antigens. e. g. a foreign substance from the environment including chemicals, bacteria, viruses, pollen e. g. molecule formed inside the body including bacterial toxins, tissue cells.

Antibody A protein produced by the body's immune system in response to antigens. An antibody is an immunoglobulin (Ig), a large, Y-shape protein. The forks of the Y are the ‘variable regions’ An antibody recognises an antigen at the variable region. In an autoimmune disease, antibodies are made against the body’s own cells.

Resistance Microbes that are not killed by antimicrobial agents such as antibiotics show resistance. Microbes which are resistant to several antimicrobials are ‘multidrug resistant’ (MDR). All classes of microbes can develop resistance AA Antimicrobial resistance is often acquired as a new mutation or transfer of genes Resistance causes millions of deaths ever year.

Vector A person, animal or microbe that carries and transmits an infectious pathogen into another living organism • Vector feeds on infected vertebrates • Microbe multiplies in vector • Microbe transmitted to new host when vector feeds again. Vector-borne diseases are often tropical & sub-tropical and where access to safe drinking-water and sanitation systems are problems. Education and sanitation are important preventative measures. Spread by • climate change • international trade • International travel

Toxin A toxin is a poisonous substance produced within living cells or organisms Toxins include small molecules, peptides and proteins Toxins cause disease following contact with or absorption by body tissues Toxins affect biological macromolecules such as enzymes and cellular receptors

Antigenic type Different individuals of the same pathogenic species may have altered surface proteins. These individuals are ‘antigenic types’ or ‘serotypes’. Different antigenic types may not recognised by host’s immune system. Having many serotypes is useful for pathogens that • Have long-lived hosts • Infect a single host repeatedly • Are easily transmissible No long-term vaccines for pathogens with frequent changes of surface protein e. g. flu, rhinovirus Pathogens with serotypes: Protoctista e. g. Plasmodium Bacteria e. g. Neisseria gonorrhoea Viruses e. g. influenza, HIV