Transcript 1PandemicsHistory

PANDEMICS THROUGHOUT HISTORY

A pandemic is defined as an unusually high outbreak
of a new infectious disease that is spreading through
the human population across a large region

“pan” – all, “demos” – people
According to the World Health Organization (WHO), a
pandemic can start when three conditions have been
met:
 emergence of a disease new to a population;

agents infect humans, causing serious illness; and

agents spread easily and sustainably among humans.

Throughout human history there have been
numerous pandemics, including the bubonic plague,
smallpox, cholera, the Spanish influenza, and most
recently HIV

Currently we are in the middle of a flu pandemic, with
the novel strain of influenza A, H1N1
THE BUBONIC PLAGUE (1347-1352)
Also known as the “Black Death”
 Caused by a bacteria (Yersinia pestis) carried by rats
and spread by fleas

Infectious agent: Yersinia pestis
 Reservoir: rats
 Vector: fleas

Kills within 3-7 days if untreated
 Killed tens of millions across Europe (between ¼ and
½ of the total population)

CHOLERA PANDEMIC (1817-1823)
A water-bourne bacteria, Vibrio cholerae
causes severe diarrhea leading to
dehydration and death
 The first pandemic is characterized by the
unprecedented spread of the bacteria
throughout Asia, starting at the Lower
Ganges River in India
 Total estimated deaths: 30 000

SPANISH INFLUENZA (1918-1920)
A very virulent influenza A subtype H1N1 strain
 Approximately 1/3 of the world’s population became
infected, and anywhere from 50 to 100 million people died
worldwide (10-20% of those infected)

 WW
I killed 15 mill., WWII 12 mill., Spanish flu 50
HIV (1981-PRESENT)

From 1981 to 2006 AIDS killed more than 25 million people
HIV (human immunodeficiency
virus) is a retrovirus that can cause AIDS (acquired
immunodeficiency syndrome)


It is thought to have originated in sub-Saharan Africa

HIV is passed through sexual relations, blood or blood
products, and mother-to-child transmission
THE “SWINE FLU”: H1N1 (APRIL 2009 - ?)

Caused by a strain of influenza A, H1N1

Originated as a mixture of swine, avian, and human
influenzas

The genetic change that allows a virus to “jump
species” is called antigenic shift
PANDEMICS OF INFLUENZA
Recorded human pandemic influenza
(early sub-types inferred)
H2N2
H2N2
H1N1
H1N1
H3N8
1895 1905
1889
Russian
influenza
H2N2
1915
Pandemic
H1N1
H3N2
1925
1900
Old Hong Kong
influenza
H3N8
1955
1918
Spanish
influenza
H1N1
1965
1957
Asian
influenza
H2N2
1975
1985
H9*
H5
H7 1980
Reproduced and adapted (2009) with permission of Dr Masato Tashiro, Director, Center for Influenza Virus Research,
National Institute of Infectious Diseases (NIID), Japan.
1965
1975
1985
2005
2010
2009
Pandemic
influenza
H1N1
1968
Hong Kong
influenza
H3N2
Recorded new avian influenzas
1955
1995
1999
1997 2003
1996
1995
2002
2005
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Animated slide: Press space bar
2015
GENETIC ORIGINS OF THE PANDEMIC (H1N1)
2009 VIRUS: VIRAL REASSORTMENT
N. American H1N1
(swine/avian/human)
Eurasian
swine H1N1
PB2
PB1
PA
HA
NP
NA
MP
NS
PB2
PB1
PA
HA
NP
NA
MP
NS
Classical swine, N. American lineage
Avian, N. American lineage
Human seasonal H3N2
Eurasian swine lineage
PB2
PB1
PA
HA
NP
NA
MP
NS
Pandemic (H1N1)
2009, combining
swine, avian and
human viral
components
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SEASONAL INFLUENZA COMPARED TO PANDEMIC —
PROPORTIONS OF TYPES OF CASES
Deaths
Requiring
hospitalisation
Clinical
symptoms
Deaths Requiring
hospitalisation
Clinical
symptoms
Asymptomatic
Seasonal influenza
Asymptomatic
Pandemic
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WHAT WE KNOW SO FAR ABOUT 2009 H1N1

Infection rate for probable and confirmed cases highest in 5−24
year age group.

Hospitalisation rate highest in 0−4 year age group, followed by 5−24
year age group.

Pregnant women seem particularly at risk

Most deaths in 25−64 year age group in people with chronic
underlying disease.

Adults, especially 60 years and old, may have some degree of
preexisting protection

There are some predictions that up to 1/3 of the population could
become infected…
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Swine Reality Video
What can we do to prepare ourselves for the influenza
pandemic?