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 and H1N1

Currently we are in experiencing flu outbreaks, the most recent, H5N1, is avian, as well as others:

Global Alert Response Outbreak News

5 September 2012- Ebola (bats?) outbreak in Democratic Republic of

Congo

4 September 2012- Hantavirus pulmonary syndrome (carried by rodents)

– Yosemite National Park, USA3 September 2012- Ebola in Uganda

30 August 2012- Ebola outbreak in DRC

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 mill.

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 Flu

Influenza is mainly a disease of water fowl

H1-16\N1-9

THE “SWINE FLU”: H1N1 (APRIL 2009 - 2010)

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

19

H7

H5

H9*

1980

1997

Recorded new avian influenzas

1996 2002

1999

2003

1955 1965 1975 1985 1995 2005

H1N1

H2N2

1889RussianinfluenzaH2N2

H2N2

1957AsianinfluenzaH2N2

H3N2

1968Hong KonginfluenzaH3N2

H3N8

1900Old Hong Kong influenzaH3N8

1918SpanishinfluenzaH1N1

1915 1925 1955 1965 1975 1985 1995 20051895 1905 2010 2015

2009PandemicinfluenzaH1N1

Recorded human pandemic influenza(early sub-types inferred)

Reproduced and adapted (2009) with permission of Dr Masato Tashiro, Director, Center for Influenza Virus Research, National Institute of Infectious Diseases (NIID), Japan. Animated slide: Press space bar

H1N1Pandemic

H1N1

RNA

Haemagglutinin

Neuraminidase

Antibodies bind to haemagglutinin; inhibit infection

Antigenic Drift

Mutation in haemagglutinin

Antibodies can no longer bind to haemagglutinin; infection and disease results

Antigenic ShiftAntigenic Shift

Human and avian flu viruses infect same host cell (eg. swine); exchange of segments occurs

New subtype of influenza with potential to cause a pandemic may be produced

GENETIC ORIGINS OF THE PANDEMIC (H1N1) 2009 VIRUS: VIRAL REASSORTMENT

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PB2PB1PAHANPNAMPNS

PB2PB1PAHANPNAMPNS

PB2PB1PAHANPNAMPNS

Classical swine, N. American lineageAvian, N. American lineageHuman seasonal H3N2Eurasian swine lineage

Eurasian swine H1N1

N. American H1N1(swine/avian/human)

Pandemic (H1N1) 2009, combining swine, avian and human viral components

SEASONAL INFLUENZA COMPARED TO PANDEMIC — PROPORTIONS OF TYPES OF CASES

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Asymptomatic

Clinicalsymptoms

Deaths

Requiring hospitalisation

Seasonal influenza Pandemic

Asymptomatic

ClinicalsymptomsDeaths

Requiring hospitalisation

WHAT WE KNOW 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. (total about 300 000 world-wide, most in Africa and Southeastern Asia)

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 have become infected…

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Canada Flu Video

What can we do to prepare ourselves for a pandemic?