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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

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

• Microbial adaptation

• Mutation

• Natural selection

• antibiotic-resistant bacteria

• Evolutionary progression

• Virulence factors

• Human Susceptibility

• immune status

• nutrition

• age

• occupation, etc.

• Human behavior and demographics

• Affect disease dissemination

• 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

• Economic development

• Dengue/DHF

• urbanization favoring mosquito vector

• Lassa fever

• urbanization favoring rodent hosts, increasing exposure

• Rift Valley fever

• dam building

•Technology and industry

• Hepatitis B and C

• transfusions, organ transplants

• Influenza (pandemic)

• possibly pig-duck agriculture facilitating reassortment

• International travel and commerce

• Dengue/DHF

• Ebola, Marburg

• In Europe and US, importation of monkeys

• HIV

• Influenza (pandemic)

• SARS

INFLUENZA

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

3 TYPES

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

THE ABILITY OF INFLUENZA TO CAUSE PANDEMICS

M1 protein

helical nucleocapsid (RNA plus NP protein)

HA - hemagglutinin

polymerase complex

lipid bilayer membrane

NA - neuraminidase

• 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

ANTIGENIC DRIFT & ANTIGENIC SHIFT

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

CONTROL & PREVENTION

• EDUCATION

• ISOLATION

• VACCINATION

• PROPER HYGIENE

VACCINE (H) & CHEMOTHERAPY (N)

DENGUE

THE VECTOR: Aedes aegypti/albopictus

INSIDE THE MOSQUITO & INSIDE

YOU...

TRANSMISSION

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.

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.

WHY DENGUE

HAS EMERGED

PREVENTION & CONTROL

THE VIRUS

LIFE CYCLE

DRUGS FOR HIV ARE BASED ON ITS LIFE

HOW YOU CAN GET IT..

DISEASE COURSE

HEPATITIS

HEPATITIS B

HEPATITIS C

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

THE HOT ZONES

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

NATURAL RESERVOIRS

TRANSMISSION

• Evidence of person to person transmission

• Close contact with body fluids (especially respiratory droplets )

• Contaminated hands, clothes, equipment; environment may also be important

ph viruses eac for finals

antigenic

antigenic

amp

spread

blood

tissues

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virus

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