History of Epidemics.

38
History of Epidemics

description

Influenza Lipid bilayer has H spikes (hemagglutinin) and N spikes (neuraminidase), i.e. H5N1 Influenza, 80 nm diameter

Transcript of History of Epidemics.

Page 1: History of Epidemics.

History of Epidemics

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Influenza•Lipid bilayer has H spikes(hemagglutinin) and N spikes (neuraminidase), i.e. H5N1

Influenza, 80 nm diameter

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1918 – 1919 Pandemic

• The Spanish Flu• 20 – 50 million deaths worldwide• Infections developed into pneumonia• U.S. soldiers brought it to the world during

WWI• Preceded by mild epidemic in

spring/summer.• H1 strain

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Other Epidemics

• 1957: 2M dead; H2 strain; “Asian Flu”• 1968: 1M dead; H3 strain; “Hong Kong

Flu”

• ~68 year cycles

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H5N1 – Avian Flu [2013]

• 650 human cases confirmed by WHO.• 386 deaths confirmed by WHO.• 125/62 in Vietnam; 25/17 in Thailand;

195/163 in Indonesia; 45/30 in China; 47/33 in Cambodia; 173/63 in Egypt.

• Since Dec. 2003.• Human-to-human transmission????

– Not yet detected.

http://www.who.int/influenza/human_animal_interface/EN_GIP_20140124CumulativeNumberH5N1cases.pdf?ua=1

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Origins of Influenza

• 412 BC – Hippocrates records epidemic• 1580 – 1st recorded pandemic• 31 major pandemics since then

(suspected)• 1933 – British scientists isolate virus

http://www.stanford.edu/group/virus/1999/rahul23/timeline.htmlhttp://www.althealth.co.uk/services/info/misc/influenza4.php

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Bubonic Plague• Yersinia pestis • Carried by fleas

(between rodents & humans)

• Respiratory transmission in later stages

• Bacteria reproduce in blood & lymph

• Very high mortality

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Pneumonic Plague

• Outbreak in Western China, Aug ‘09.

• 11 reported cases – all fatal.

• Quarantine.• Ziketan in Qinghai

Province.

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Origins of the Plague

• 430 BC – 1st epidemic recorded in Athens• Peloponnesian War• Killed 300,000 – 1/3 of Greek population • Several epidemics from 500s to 700s AD

ranging from Mediterranean Europe to Central and Southern Asia

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Plague in Europe

• Returns to Europe in 1300s – after 600 years with few signs

• Now known as the “Black Death”• Up to 28M Europeans killed (~40% of

population)• Smaller epidemics over next 400 years

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Plague

• 1300s – 1/3 of Asian population is killed• By late 1800s – new epidemics in China,

Africa and elsewhere• 1894 – epidemic in Hong Kong; bacterium

(the “etiological agent”) is isolated• 1994 – Possible epidemics in India,

Malawi, and Mozambique

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Confusing the Plague

• Historical records may not be accurately interpreted

• Can be confused with other diseases, such as typhoid fever

http://www.macalester.edu/~cuffel/molecularplague.htm

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Small Pox (Variola)

• Virus infects internal organs

• Later stage can result in lesions on skin

• Some forms can have a mortality rate >20%; others have a low rate

• Respiratory transmission

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Origins of Smallpox

• Probably in Africa – thousands of years ago

• 1350 BC – 1st recorded epidemic in Egypt• 5th Century – reached Europe• Many major epidemics in Europe until

1400s• Building immunity in population

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Small Pox in the Western Hemisphere

• Native Americans had little or no exposure to the virus

• Little immunity in the population• Killed a large portion of Native Americans

as Europeans colonized the West– Unintentional and intentional!

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Vaccination

• ~1050 A.D. – Buddhist nun in China practices “variolation”

• Grinds up smallpox scabs into powder• Blows the powder up nostrils of uninfected

patient• Mild disease results (~97%)• Practiced in much of Asia by 1700s

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Vaccination in Europe

• 1790s – Edward Jenner uses cow pox scabs to stimulate immunity– Experiments with an 8 year old boy

• 1800 – 100,000 people are vaccinated• 1967 – WHO begins eradication effort• 1972 – last vaccinations in US general population• 1977 – last reported case in Somalia• 1980 – World declared free of smallpox

– Except for two labs (U.S. and U.S.S.R.)

http://dermatology.about.com/cs/smallpox/a/smallpoxhx.htm

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War & Infectious Disease

• Treatment of soldiers– Wounds, extreme physical conditions,

trenches, chemical exposure, etc.• Uprooted civilians

– Crowded refugee camps, reduced healthcare.• Destruction of infrastructure

– Water & sewage treatment, food distribution, etc.

• E.g. cholera, typhus, malaria.

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Poverty & Infectious Disease

• Little access to healthcare.• Poor nutrition.• Hazardous jobs.• Proximity to toxic environments.• Less education.

• E.g. HIV/AIDS, TB, malaria, cholera, and more.

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The “Big Three”

• HIV/AIDS• TB• Malaria

• Diarrheal diseases• Pneumonia

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How Do We Know About Microorganisms?

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First Microscopes

• 17th Century• Robert Hooke – the “cell theory”

observed cork• Antoni van Leeuwenhoek – “animalcules”

observed living samples

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Hooke

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van Leeuwenhoek (fig. 1.2)

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Biogenesis

• 1861 – Louis Pasteur uses flasks with S-shaped neck

Boils the nutrient broth, air can get into flask, but nothing grows

This is considered the definitive proof of Biogenesis!

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Fig. 1.3

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Microbiology’s “Golden Age”

1857 – 1914• Pasteur demonstrates that yeasts ferment

sugars beer & wine• Bacteria can cause food spoilage• Pasteurization!

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Can Microbes Cause Disease?

• Germ Theory of Disease says, “YES!”• 1860s – Joseph Lister uses phenol to

disinfect surgical wounds• 1860s – US Civil War: lots of battlefield

surgery led to gangrene, until bromine was introduced as disinfectant

• Also, better sanitation was needed to prevent cholera and dysentery

• Ignaz Semmelweis

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Koch’s Postulates

• Method of proving that a particular microbe causes a disease

• Isolate an organism from the diseased tissue (from human patient)

• Grow them in pure culture• Inject them into animal to cause the disease• Re-isolate the bug/germ/microbe from the

animal

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Fig. 14.3

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Robert Koch, 1870s & 1880s

• Used his postulates to discover:Bacillus anthracisMycobacterium tuberculosisVibrio choleraeStaphylococcus aureus

• Never done for Treponema pallidum

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Koch’s Postulates in Modern Microbiology

• Still the standard procedure

• Used in 2004 for SARS

• Never done for Treponema pallidum