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 more recently HIV

In 2009, we were faced with another pandemic - with the novel strain of influenza A, H1N1 – otherwise known as swine flu

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-borne bacteria, Vibrio cholerae causes severe diarrhea leading to dehydration and death

The first pandemic was characterized by the unprecedented spread of the bacteria throughout Asia, starting at the Lower Ganges River in India

Total estimated deaths: 30 000

SMALLPOX (18TH CENTURY ONWARDS…)

In total, smallpox killed more than 300-500 million people around the world in the 20th century

A very contagious disease caused by viruses, Variola major (killed 30 to 30 percent of its victims) and Variola minor (killed about 1 percent)

Smallpox localizes in the small blood vessels in the skin, mouth and throat – causes a rash and then, fluid-filled blisters

Can leaves scars, blindness, limb deformities in survivors

SMALLPOX….CONTINUED

Smallpox has been around since 10,000 BC Killed an estimated 400,000 Europeans in the 18th

century

Smallpox devastated Aboriginal populations in North and South America (90 to 95 percent died)

As recently as 1967, around 15 million people contracted the disease and 2 million of those died

The disease is the only human infectious disease that has been eradicated (1979 – due to vaccination campaigns)

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 (human immunodeficiency

virus) is a retrovirus (RNA virus that produces DNA ,which is incorporated into the host DNA)

o HIV 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

HIV AND AIDS

2.6 million new people were infected with HIV in 2009

1.8 million people died in 2009

The number of new infections and AIDS-related deaths are declining steadily due to antiretroviral therapy

PEOPLE LIVING WITH HIV (2008)

In 1990, 8 million people were living with HIV, in 2009 it was 33 million (the population of Canada)

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

Influenza is mainly a disease of water fowl

H1-16\N1-9

PANDEMICS OF INFLUENZA

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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

25

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 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 a pandemic?