Transcript disease

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
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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