Infectious Diseases
Chapter 20, section 2
Disease is a major focus of
environmental health
Two categories:
• transmissable (or infectious) disease – can
spread from one person to another; ex. malaria,
flu, TB
• nontransmissable disease – cannot be
transmitted from one person to another; ex.
cancer, heart disease, respiratory disorders
Despite our technology, disease kills most of us
Disease has a genetic and environmental basis
–
Poverty and poor hygiene can foster
illnesses
Q1. What is the difference between a transmissible and
nontransmissable disease?
Q2. Give two examples of each.
Q3. What are the top three leading causes of death
worldwide, according to the pie graph at right?
Infectious diseases kill millions
• Infectious diseases kill 15 million
people per year
– Half of all deaths in developing
countries
– Developed countries have better
hygiene, access to medicine, and
money
• Vector = an organism that transfers
pathogens to a host (Ex: mosquito,
snail, fly)
• Pathogen – something that causes
disease (bacteria, fungus, virus)
Q4. Refer to the figure above. What are the six
deadliest infectious diseases for people in order of
the number of deaths they cause each year?
Q5. Define and give an example of a pathogen.
Q6. Define and give an example of a vector.
Pathogens that cause disease:
Viruses
HIV
(AIDS)
Smallpox
Protozoa
Hepatitis B
Ebola
On this scale, a human hair would be 6 meters (20 feet) wide
Plasmodium
(malaria)
1 micrometer
10 micrometers
Bacteria
Vibrio cholerae
(cholera)
Treponema pallidum (syphilis)
6 micrometers
Myobacterium
tuberculosis
(tuberculosis)
Q7. List four pathogens
that are viruses.
Q8. List three
pathogens that are
bacteria.
Ways infectious diseases spread
Pathogens can infect people through different routes:
• Through the air
• Through contaminated water
• Through contaminated food
• By a vector
• Through the skin
• From mother to fetus/newborn
• By contact with an infected person’s bodily fluids
Q9. List a disease caused by each of the above
transmission routes. You may use your disease
flashcards.
How do the cause of deaths for rich
and poor countries compare?
Lung
cancer
Q10. List the top three causes of death for high
income countries. Are any of these infectious
diseases? If so, which ones?
Q11. List the top three causes of death for low
income countries. Are any of these infectious
diseases? If so, which ones?
What factors have reduced infectious
disease in high income countries?
• Vaccinations
• Better sanitation – clean water
• Antibiotics and other medicines
Q12. Can you list four infectious diseases that YOU
have been vaccinated against?
Q13. What type of pathogen is affected by antibiotics?
Anopheles mosquito (vector)
in aquatic breeding area
eggs
adult
larva
pupa
1. Female
mosquito bites
infected human,
ingesting blood
that contains
Plasmodium
gametocytes
4. Parasite invades
blood cells, causing
malaria and making
infected person
a new reservoir
2. Plasmodium
develops in
mosquito
3. Mosquito injects Plasmodium
sporozoites into human host
“Malaria is a mosquito-borne
disease caused by a parasite.
People with malaria often
experience fever, chills, and flulike illness. Left untreated, they
may develop severe
complications and die. In 2010
an estimated 219 million cases
of malaria occurred worldwide
and 660,000 people died, most
(91%) in the African Region.”
(CDC website)
Q14. What vector carries
malaria?
Q15. What organism infects
the blood and actually causes
malaria
Q16. What are the symptoms
of malaria?
How to reduce malaria –
• Eliminate breeding grounds for mosquitos (reduce standing water)
• Kill mosquitos with insecticides
• Avoid getting bitten – use insect repellent and mosquito nets for sleeping
• Take anti-malarial drugs if traveling to areas affected by malaria
Q17. How could an individual protect
themselves from getting malaria?
Q18. How could a community reduce
the number of cases of malaria?
Many diseases are increasing
• Tuberculosis, acquired
immunodeficiency syndrome
(AIDS), and the West Nile virus
have increased in recent years
• Our mobility spreads diseases – the
more globalization occurs, the
more people travel and contact
other people
Q19. List three infectious diseases that are
increasing worldwide.
Q20. When did the highest number of cases
of West Nile virus occur in the U.S.? What
part of the U.S. had the disease first?
Q21. How does globalization affect the
spread of disease?
Some diseases cross from animals to
humans
Avian flu – people in Asia who work with live
birds (ducks, geese) can get the virus
Swine flu – also called H1N1
Q22. Name two animals from which people can contract a type
of flu virus.
Current issues with infectious diseases
• Drug-resistant strains of bacteria have
developed in response to the increased use of
antibiotics
Original pop treated with antibiotic:
Q23. Using the diagram above,
explain how the final population
became more resistant after the
use of an antibiotic.
Q24. MRSA, a drug-resistant
form of staph bacteria, was ___%
resistant to antibiotics by 2001.
Current issues with infectious diseases
Climate change will expand the range of
diseases
Q25. How could warmer global temperatures affect the spread
of diseases such as dengue fever and malaria, which are
spread by mosquitos?
Solutions
Infectious Diseases
Increase research on tropical
diseases and vaccines
Reduce poverty
Q26. List five ways to
prevent or reduce the
incidence of infectious
diseases throughout the
world.
Decrease malnutrition
Improve drinking water quality
Reduce unnecessary use of antibiotics
Educate people to take all of an
antibiotic prescription
Reduce antibiotic use to promote
livestock growth
Careful hand washing by all
medical personnel
Immunize children against major viral
diseases
Oral rehydration for diarrhea victims
Global campain to reduce HIV/AIDS
Q27. One textbook
says that this is the
best weapon to fight
the spread of viruses.
Write down the
solution that the
arrow indicates.
Bioterrorism
From the CDC website:
“A bioterrorism attack is the deliberate release of viruses,
bacteria, or other germs (agents) used to cause illness or
death in people, animals, or plants. These agents are typically
found in nature, but it is possible that they could be changed
to increase their ability to cause disease, make them resistant
to current medicines, or to increase their ability to be spread
into the environment. Biological agents can be spread through
the air, through water, or in food. Terrorists may use biological
agents because they can be extremely difficult to detect and
do not cause illness for several hours to several days. Some
bioterrorism agents, like the smallpox virus, can be spread
from person to person and some, like anthrax, can not. ”
Bioterrorism using pathogens
Q28. What are six agents that could be used by bioterrorists?
Q29. What are two ways to reduce threats from bioterrorists?
Category
A
B
C
Definition
Pose the highest risk
to national security
because they
•Can be easily
disseminated or
transmitted from
person to person
•Result in high
mortality rates
•Have potential to
cause public panic
and social disruption
•Require special
preparedness
actions
Pose the second
highest risk because
they
•Are moderately
easy to disseminate
•Result in low
mortality rates
•Require
enhancement of
diagnostic and
surveillance
capability
Emerging pathogens
that could be
engineered for mass
dissemination
because they:
•Are available
•Are easily produced
and disseminated
•Have potential for
high mortality rates
Examples
•Anthrax
•Botulism
•Plague
•Smallpox
•Tularemia
•Viral hemorrhagic
fevers (e.g. Ebola,
Marburg)
•West Nile Virus
•Caliciviruses
•Hepatitis A
•Ricin toxin
•Salmonella
•Diarrheagenic E.
coli
•Influenza
•SARS
•Rabies
•Multi-drug resistant
tuberculosis
•Yellow fever
•Tickborne
hemorrhagic fever