Epidemiology and Surveillance: Lessons from Past Pandemics

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Epidemiology and Surveillance Lessons from Past
Pandemics

• Arnold S. Monto, MD
• Professor of Epidemiology
• University of Michigan School of Public Health
• Founding Director
• University of Michigan Bioterrorism Preparedness
  Initiative
• Ann Arbor, MI

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Basic Questions

• When will the virus arrive and spread? How long
  from the source?
• What will the principal age and other risk groups
  be?
• How many will be affected?
• Morbidity?
• Mortality?

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Source of Pandemic Viruses
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Effects of Past Pandemics on the US
Source NVPO.
5
The 1918 Pandemic in Asia and Africa
Influenza-Associated Deaths

• Asia
• India 12.5 million deaths (higher than bubonic
  plague)
• Japan 257,000 deaths
• Rest of Asia 3,000,000 deaths
• Africa
• Union of South Africa 139,471 deaths out of
  6,100,000 population
• Madagascar 114,000 deaths out of 3,250,000
  population

Jordan, ED. Epidemic Influenza, AMA. Chicago,
1927.
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Review of Past Pandemics

• Age Specificity
• Traditional view U or J shaped curves in
  most pandemics W shaped curve in 1918.
• Variations 1889-1890Reports from UK of high
  mortality in young adults
• Sparing of elderly in 1918
• Relatively higher death rates in young adults
  in more recent pandemics
• Will past history predict the future?

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Pneumonia and Influenza Mortality in Influenza
Pandemics
Modified from Dauer Serfling. Am Rev Resp Dis.
1961 8315-28.
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Age-Specific Influenza Death Rates Among Females
in England and Wales, 1918
?
Nguyen-Van-Tam, JS, et al. Vaccine.
200321762-68.
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1957
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Influenza Attack Rates by Age in Tangipahoa
Parish, Louisiana August, 1957
Langmuir AD. Am Rev Resp Dis. 1961835.
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1968
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Weekly Incidence of Influenza-like Diseasesin
Hong Kong June to September 1968
June
July
Aug.
Sept.
Week Ending
Cockburn et al. Origin and progress of the
1968-69 Hong Kong Influenza epidemic. Bull. Wld
Hlth Org. 196941345-8.
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Peak Influenza Activity in the US by State and
Week 1968-69
Oct.
Nov.
Dec.
Jan.
Feb.
Week Beginning
Sharrar RG. National Influenza Experience in the
USA, 1968-69. Bull. Wld Hlth Org. 196941361-6.
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Number of Episodes of Illness, Healthcare,
Utilization, and Death Associated with Moderate
and Severe Pandemic Influenza Scenarios
Estimates based on extrapolation from past
pandemics in the United States. Note that these
estimates do not include the potential impact of
interventions not available during the 20th
century pandemics. Source NVPO.
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Conclusions

• The 1918 outbreak was unique in terms of numbers
  of persons involved and age groups affected.
  There is a question as to whether 1889-90
  affected young adults disproportionately.
• It is difficult from historic records to document
  the presence or effect of the 1918 virus before
  the second wave. Once that wave began, it
  spread quickly.
• The 1957 virus probably spread for at least 6
  weeks in China, starting in February, before
  emerging. It affected South America before
  spreading to North America in the early autumn.
• The spread of the 1968 virus was well documented
  from Hong Kong in July. The peak in the US was
  December-January.
• Numbers affected in the future will be based on
  multiple factors currently unknown, and any
  estimates must be viewed as provisional.