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VIRUSES OF PUBLIC HEALTH
IMPORTANCEMarch 2012
PUBLIC HEALTH“protecting and improving health through education and promotion of
healthy lifestyles and research for disease and injury prevention”
Saturday, March 3, 2012
EMERGING INFECTIONS
Saturday, March 3, 2012
EMERGING INFECTIONS
Saturday, March 3, 2012
FACTORS THAT LED TO EMERGENCE
• Introduction of the agent into a new host population, originating from:
• environment
• another host species
• variant of an existing human infection
• Establishment and further dissemination within the new host population
Saturday, March 3, 2012
FACTORS THAT LED TO EMERGENCE
• Microbial adaptation
• Mutation
• Natural selection
• antibiotic-resistant bacteria
• Evolutionary progression
• Virulence factors
Saturday, March 3, 2012
FACTORS THAT LED TO EMERGENCE
• Human Susceptibility
• immune status
• nutrition
• age
• occupation, etc.
• Human behavior and demographics
• Affect disease dissemination
Saturday, March 3, 2012
FACTORS THAT LED TO EMERGENCE
• Changing ecosystems / land use
• Argentine, Bolivian hemorrhagic fever
• changes in agriculture (grassland to maize) favoring rodent host
• Hantaviruses
• Ecological or environmental changes increasing contact with rodent hosts
• Rift Valley fever
• agriculture, irrigation
Saturday, March 3, 2012
FACTORS THAT LED TO EMERGENCE
• Economic development
• Dengue/DHF
• urbanization favoring mosquito vector
• Lassa fever
• urbanization favoring rodent hosts, increasing exposure
• Rift Valley fever
• dam building
Saturday, March 3, 2012
FACTORS THAT LED TO EMERGENCE
•Technology and industry
• Hepatitis B and C
• transfusions, organ transplants
• Influenza (pandemic)
• possibly pig-duck agriculture facilitating reassortment
Saturday, March 3, 2012
FACTORS THAT LED TO EMERGENCE
• International travel and commerce
• Dengue/DHF
• Ebola, Marburg
• In Europe and US, importation of monkeys
• HIV
• Influenza (pandemic)
• SARS
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INFLUENZA
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THE BASICS...
• Influenza is an acute, viral respiratory infection
• When to suspect?
• Fever, chills, headache, aches and pains throughout the body, sore throat which may lead to bronchitis or pneumonia
• Vomiting and diarrhea may also occur
• Many deaths have been attributed to influenza
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3 TYPES
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PANDEMICS
• PANDEMIC: world wide spread of infection occurring in many countries simultaneously
• INFLUENZA PANDEMICS: occur approximately every thirty years
• REASON FOR OCCURRENCE: new strain of the virus emerges for which people have no immunity and there are no vaccines available
Saturday, March 3, 2012
Saturday, March 3, 2012
Saturday, March 3, 2012
THE ABILITY OF INFLUENZA TO CAUSE PANDEMICS
M1 protein
helical nucleocapsid (RNA plus NP protein)
HA - hemagglutinin
polymerase complex
lipid bilayer membrane
NA - neuraminidase
Saturday, March 3, 2012
• Haemagglutinin (H)
• attaches the virus to cells and allows the viral envelope to fuse with the cell membrane and enter cells
• Neuraminidase (N)
• allow the release of viruses to infect other cells
THE ABILITY OF INFLUENZA TO CAUSE PANDEMICS
Saturday, March 3, 2012
ANTIGENIC DRIFT & ANTIGENIC SHIFT
Saturday, March 3, 2012
ANTIGENIC DRIFT & ANTIGENIC SHIFT
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LIFE CYCLE & TRANSMISSION
• The virus is spread by inhalation or by direct contact
• Reservoirs of infection: primarily humans, but birds and pigs can act as reservoirs
• Multiple host status = mixing of flu types
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CONTROL & PREVENTION
• EDUCATION
• ISOLATION
• VACCINATION
• PROPER HYGIENE
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VACCINE (H) & CHEMOTHERAPY (N)
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VACCINE (H) & CHEMOTHERAPY (N)
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Saturday, March 3, 2012
DENGUE
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THE VECTOR: Aedes aegypti/albopictus
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INSIDE THE MOSQUITO & INSIDE
YOU...
Saturday, March 3, 2012
TRANSMISSION
Saturday, March 3, 2012
PATHOGENESIS1.The virus is inoculated into humans with the mosquito saliva.
2.The virus localizes and replicates in various target organs, for example, local lymph nodes and the liver.
3.The virus is then released from these tissues and spreads through the blood to infect white blood cells and other lymphatic tissues.
4.The virus is then released from these tissues and circulates in the blood.
Saturday, March 3, 2012
PATHOGENESIS5.The mosquito ingests blood containing the virus.
6.The virus replicates in the mosquito midgut, the ovaries, nerve tissue and fat body. It then escapes into the body cavity, and later infects the salivary glands.
7.The virus replicates in the salivary glands and when the mosquito bites another human, the cycle continues.
Saturday, March 3, 2012
WHY DENGUE
HAS EMERGED
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PREVENTION & CONTROL
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HIV
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THE VIRUS
Saturday, March 3, 2012
LIFE CYCLE
Saturday, March 3, 2012
DRUGS FOR HIV ARE BASED ON ITS LIFE
CYCLE
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HOW YOU CAN GET IT..
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DISEASE COURSE
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HEPATITIS
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HEPATITIS B
HEPATITIS C
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SARS
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THE OUTBREAK• In November 2002, highly contagious and severe
atypical pneumonia were observed in the Guangdong Province of southern China
• The virus was spread to Hong Kong in February 2003 by a doctor who died 10 days after admission into local hospital = a mysterious death
• Similar outbreaks occurred at different local communities subsequently
Saturday, March 3, 2012
THE HOT ZONES
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SEVERE ACUTE RESPIRATORY SYNDROME
(SARS)
• Cause : SARS CoV
• Highly infectious
• Mainly affects adults
• Superspreading events important in transmission process
• No reports of transmission occurring before onset of symptoms
Saturday, March 3, 2012
Saturday, March 3, 2012
Saturday, March 3, 2012
NATURAL RESERVOIRS
Saturday, March 3, 2012
TRANSMISSION
• Evidence of person to person transmission
• Close contact with body fluids (especially respiratory droplets )
• Contaminated hands, clothes, equipment; environment may also be important
Saturday, March 3, 2012