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Unit 4, Key Area 3 & 4: What you should know 1. Infectious diseases caused by ___________________ such as bacteria and viruses are transmitted by many means including _________________ air, body fluids and ____________________ organisms. 2. _____________________, antisepsis, good ___________________, clean water and removal of vectors are some of the ways by which transmission of infectious diseases can be controlled. 3. The study of an infectious disease’s outbreak and the factors that affect its spread is called _________________________________. The spread of a disease that occurs occasionally is described as ______________________, one that occurs as a regular number of cases in a particular area as ____________________, one that occurs as an unusually high number of cases in an area as __________________________ and one that occurs as a global epidemic as _______________________. 4. Weakened or altered forms of an infectious pathogen or its __________________________ are used as ____________________________. These are administered to people by _______________________ so that they will develop active ___________________________ to the disease but not suffer the disease. 5. The safety and ________________ of new vaccines must be established by _______________ trials before they can be licensed for use. 6. A clinical trial ______________ is ___________________ and and double-blind placebo-controlled to to allow eliminate a valid ____________________ to be made. _____________________ error is reduced by using a very large number of people. 7. Within a population where most individuals are immune to an infectious disease, vulnerable ________________________ individuals are protected from it by ____________________ immunity. 8. The percentage of immune individuals in a population above which a disease no longer persists is called the herd immunity _______________________. It depends on the pathogen’s ______________________, the vaccine’s efficacy and the population’s contact _________________________. 9. Herd immunity _____________ can to be difficult afford mass to establish vaccination if or the if country the ______________________ by a large percentage of the population. is too vaccine is 10. By altering their antigens, some pathogens are able to ___________________ the immune responses made by their ______________________. 11. Extensive antigenic _______________________ in the pathogens that cause ______________ and trypanosomiasis has so far prevented scientists from developing a successful vaccine against them. Antigenic variation in the __________________ virus makes it necessary to keep developing new vaccines. 12. Some pathogens take advantage of some part of the human immune system and launch a direct ________________ on it. HIV attacks ___________________ and causes AIDS. Tuberculosis bacteria avoid immune ____________________ by surviving inside ________________________. o o o o o o o o o o o o antigens attack bias clinical comparison detection efficacy endemic epidemic epidemiology evade experimental o o o o o o o o o o o o helper T cells herd host hygiene immunity influenza inhaled malaria non-immune pandemic parameters pathogens o o o o o o o o o o o o phagocytes poor quarantine randomised rejected sporadic threshold toxin vaccination variation vector virulence