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Environmental Hazards and Human Health, Part 2
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Transcript of Environmental Hazards and Human Health, Part 2
Environmental Hazards and
Human Health, Part 2
Causes of global deaths
Infectious diseases
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 18-4Figure 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
• 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