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Environmental Hazards and Human Health, Part 2 Causes of global deaths 5% Cardiovascular diseases 8% 29% 9% Infectious diseases Cancers Respiratory and digestive diseases 10% Injuries 13% Maternal and perinatal conditions 26% Other Infectious diseases 8% 9% 6% 30% 12% 14% 21% Respiratory infections HIV/AIDS Diarrheal diseases Tuberculosis Malaria Childhood diseases Other Some definitions • Disease – Chronic – Acute • Epidemic • Pandemic Transmissible (infectious) disease: one that is caused by a living organism • Pathways for infectious disease in humans. Figure 18-4 Common Vectors That Transmit Disease Mosquito Tick Mouse Deer Examples of Vector-Borne Diseases • Mosquito-borne – West Nile Virus – Malaria – Dengue – Yellow Fever • Tick-borne – Lyme Disease – Rocky Mountain Spotted Fever • Hanta Virus (mice droppings) • Bubonic Plague (fleas) Characteristic bull rash caused by Lyme disease How Weather Affects Vector-Borne Diseases • Temperature • Humidity • Surface water • Tropical and subtropical regions How Weather Affects Vector-Borne Diseases • • • • • Tropical and subtropical regions Temperature Humidity Surface water What might happen with future predicted climate changes? Climate Change –Larger geographic area where disease is common –Intensity and duration of outbreaks –Altered seasonal distributions Examples • Mosquitoes develop more rapidly • Mosquitoes bite more frequently • Viral load in mosquitoes is higher • Because more people are infected, more mosquitoes become carriers that transmit disease Historic Infectious Diseases • Diseases of poor sanitation – Hepatitis – Cholera – Diarrheal • Plague • Malaria • Tuberculosis Plague • Bubonic plague, Black Death • Caused by a bacterium carried by fleas and thus their hosts Malaria – Death by Mosquito Tuberculosis • Caused by a bacterium that infects the lungs • Spread when someone coughs • Highly infectious • Bacterial cells can live in air for several hours Growing Global Threat from Tuberculosis • The highly infectious antibiotic-resistant tuberculosis (TB) kills 1.7 million people per year and could kill 25 million people by 2020. • Recent increases in TB are due to: – Lack of TB screening and control programs especially in developing countries due to expenses. – Genetic resistance to the most effective antibiotics. Growing Germ Resistance to Antibiotics Emergent infectious diseases • Previously not described, or • Have not been common for at least the previous 20 years • Examples: – HIV/AIDS – Ebola – Mad Cow – Avian flu – West Nile – SARS Emergent diseases Ebola hemorrhagic fever Bovine Spongiform Encephalopathy • Mad Cow Disease • Caused by prions Avian flu • H1N1 virus • In 1918 killed an estimated 40 million people • 2006 a closely related (H1N5) emerged from Asia, passed from domestic birds to people • 2010 a new emergence of H1N1 first found in Mexico (swine flu) SARS • Sudden Acute Respiratory Syndrome • Severe form of pneumonia first identified in 2003 • 8000 cases, 750 that year • Virus is passed from person to person through airborne and surficial means • Virus can live up to 6 hours in the open environment
