Emerging Infections

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Emerging Infections

• Angela McLean
• Institute for Emergent Infections of Humans
• James Martin 21st Century School
• Zoology Department
• Oxford University

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Definition Emerging infections

• More cases of an old infection (eg TB is
  re-emerging)
• Newly discovered / detected (eg Helicobacter
  pylori has been around for ages, but only
  recognised in the last couple of decades)
• Genuinely new
• SARS
• HIV
• BSE
• H5N1 flu

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20th Century Adult Mortality Rates in the UK

• Males Females
• Deaths per million population

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Causes of death in Chile1909 and 1999
Weiss McMichael 2006
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Life expectancy at birth 8 countries 1950 - 2005
Weiss McMichael 2006
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Significant events in public health
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25 years of HIV/AIDS
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Emerging and re-emerging infectious diseases
1996 - 2004
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Monthly summary of EID events
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EID events December 2007
Influenza H5N1 China, Egypt Indonesia,
Myanmar Pakistan, Vietnam, UK
CJD UK
Brucellosis China
Coccidiodo mycosis USA
Rift Valley Fever Sudan
Undiagnosed neurological illness USA
Chikungunya Indonesia
Psittacosis Netherlands, Brazil, USA
Ebola Haemorrhagic Fever Uganda
Plague Uganda
Trypanosomiasis, foodborne Venezuela
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Three Big Questions

• Whats out there?
• In humans already
• Known in animals
• Unknown
• Which are likely to trouble humans?
• Making new contacts with new infectious agents
• What are species barriers
• Understanding pathogenesis
• How do pathogens adapt to humans?
• If they do, could we control them?
• Establishing good surveillance
• Making drugs and vaccine
• Understanding speed of spread
• Calculating minimum or optimal interventions

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What is out there?

• In humans already
• How should we deal with known infections of
  humans (eg HIV, TB, malaria, dengue, MRSA
• Known in animals
• How do we plan for the emergence of novel
  infections that we know, expect, and cannot
  prevent influenza
• Unknown
• What can we do that is cautious and proportionate
  about unknown infections that may emerge in the
  future?

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Which are likely to trouble us?Environmental
change

• New situations for human contact with novel
  agents
• Bushmeat
• xenotransplantation
• Better situations for the spread of novel agents
  that have crossed into humans
• increased sexual contact for HIV
• rapid international travel for SARS
• Environmental change affecting vectors

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Which are likely to trouble us?Genetic change

• Mostly we can just classify, but after the fact
• We dream of being able to predict sequence change
  that would enable cross-species transmissions
• Even for influenza, the determinants of what
  strain will emerge next are not understood
• We are remarkably ignorant about why some
  infections make us sick and others are without
  symptoms

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Will we be able to control future threats?

• Developing good surveillance
• New drugs and vaccines
• Understanding how fast infections spread and
  evolve
• Calculating sufficient interventions to control
  spread or the likely impact of the best we can
  manage

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Three Big Questions

• Whats out there?
• In humans already
• Known in animals
• Unknown
• Which are likely to trouble humans?
• Making new contacts with new infectious agents
• What are species barriers
• Understanding pathogenesis
• How do pathogens adapt to humans?
• If they do, could we control them?
• Developing good surveillance
• Making drugs and vaccine
• Understanding speed of spread
• Calculating minimum or optimal interventions

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Further Reading

• 6 pages
• Weiss McMichael (2004) Social and Environmental
  risk factors in the emergence of infectious
  diseases Nature Medicine vol 10 pp S70-s76
• 40 pages
• The world health report 2007 - A safer future
  global public health security in the 21st century
  http//www.who.int/whr/2007/en/
• 750 pages
• Laurie Garrett (1996) The Coming Plague Newly
  Emerging Diseases in a World Out of Balance

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Which viruses will we work on?

• HIV
• Dengue
• Hepatitis C Virus
• Influenza

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Why those four?
Estimated deaths from viral infections 2003
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Why study adaptation to humans?

• 3 steps to emergence
• New transmission to humans
• Some transmission amongst humans
• Adaptation to become an efficient pathogen of
  humans
• Evidence that step 1 is not highly unusual
• H5N1 currently few clusters
• Simian Foamy Virus in zoo keepers
• SARS immunity in Hong Kong wet market workers