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Adams Environmental Science Chapter 20 Section 2 The Environment’s Role in Disease Infectious diseases are caused by pathogen, organisms that cause disease. These diseases spread through person to person contact through the air or drinking water. A host is an organism in which a pathogen lives all or part of its life. Waterborne Disease About ¾ of infectious diseases are transmitted through water. In developing countries, there is a shortage of water so the water supply is used for drinking, washing and sewage disposal. These are good breeding grounds for pathogens. Organisms that transmit diseases are called vectors. Cholera Deadliest waterborne diseases come from drinking polluted water by human feces. Cholera causes the body to lose water by diarrhea and vomiting. It causes the most infant mortality. Malaria Once the world’s leading cause of death. Caused by parasitic protists and is transmitted by a bite from female mosquitoes. No vaccine for malaria exists but there are preventative measures to control mosquitoes. Environmental Change and Disease We alter the environment to make it more suitable for pathogens to live and reproduce. Many organisms spread through soil that is contaminated with feces. Ex. Hookworm Adams Environmental Science Chapter 20 Section 2 People are infected by walking barefooted and contaminated food. Antibiotic Resistance Antibiotics cause pathogens to evolve Large quantities of antibiotics are feed to live stock to speed growth causing Salmonella and E.Coli to evolve. Treating human illnesses has also caused diseases such as pneumonia and tuberculosis to evolve Emerging viruses Viruses that was unknown 100 years ago. Ex. HIV/AIDS, ebola virus, West Nile virus. We do not have any effective drugs to treat viral diseases. Vaccines are only effective to a virus that is already present. Cross Species Transfers When pathogens cross over from its original host to a new host. Ex. HIV, West Nile Recent Examples include the bird flu and the swine flu.
