Epidemiology

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Epidemiology

• Bernd Sebastian Kamps
• Christian Hoffmann

Prepared By ABM Alauddin Chowdhury
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Epidemiology of SARS
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Hot zones of SARS

• China, Hanoi, Hong Kong, Singapore, Toronto "hot
  zones" of SARS
• SARS first took root in hospital settings.
• Where staff, unaware that a new disease had
  surfaced
• Exposed themselves to the infectious agent
  without barrier protection

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Rapid Increase of Number of Worldwide Cases

• Exceeded 4000 on 23 April
• Exceeded 5000 on 28 April
• Exceeded 6000 on 2 May
• Exceeded 7000 on 8 May
• 200 new cases each day
• More than 8,000 as of July 3, 2003

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SARS Epidemic Summary

• SARS first detected in Guangdong, Nov 2002
  took 3 months to spread Hong Kong
• Outbreaks to date restricted to families, often
  living in high-density accommodation hotels,
  hospitals
• Influenza infects millions of persons
• Remarkable extent of air travel

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Modeling the Epidemic

• 2 major studies published
• 2.7 secondary infections generated
• Transmission rates fell during
• epidemic, primarily due to
• reductions in population contact rates
• improved hospital infection control
• more rapid hospital attendance by
• symptomatic individuals

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Starting Point

• Highly contagious, severe atypical pneumonia in
  Guangdong, China
• Many cases were rapidly fatal
• Growing concern about illness
• High mortality death within hours
• 305 cases disease
• 5 deaths

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Global Spread

• Feb. 21, 2003, an infected doctor spent night at
  Hong Kong hotel became ill died 10 days later.
• Seeded outbreaks of cases in hospital systems of
  Hong Kong, Vietnam, and Singapore
• Disease spreading around the world

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Hong Kong

• The physician from Guangdong infected 12 other
  persons.
• Two individuals were responsible for outbreaks in
  two local hospitals.
• Implemented enhanced infection-control procedures
  in all hospitals

Source MMWR 200352241-248
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Hong Kong March 2003

• A further SARS outbreak occurred
• 320 SARS cases in less than 3 weeks
• The probable index patient was suffering from
  chronic renal failure person-to-person spread
  use of communal facilities.
• SARS virus may spread through the sewage systems
  of buildings.

Source Government of Hong Kong Special
Administrative Region
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Hong Kong April 2003

• Rate of confirmed SARS cases fell to less than 20
  per day.
• Hong Kong epidemic seems under control.
• Reduction in contact rate between infectious
  individuals and the rest of the population

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Hong Kong June 2003

• By June 16, 1755 cases diagnosed
• 295 patients (16.8) died
• 1386 patients (79.0) recovered
• 30 occurred in healthcare workers
• 55 nurses
• 15 doctors
• 27 support staff
• 8 medical workers died by June 2
• June 23, WHO removed Hong Kong

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Epidemic curve, Hong Kong June 16
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Vietnam

• February 26, outbreak in Vietnam began
• By March 5, secondary probable SARS cases
  identified among health care workers in Hanoi
• 63 people infected
• On April 28, WHO removed Vietnam from the list of
  affected areas

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Vietnam

• Dr Carlo Urbani, died of SARS on March 29 2003

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Vietnam

• WHO Recommendations
• Prompt identification of SARS
• Effective isolation of SARS patients
• Protection of medical staff
• Isolation of suspected SARS cases
• Exit screening of international travelers
• Timely and accurate reporting
• Sharing information with other authorities or
  governments

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Toronto

• February 2003, SARS introduced
• March 8 and 9, 5 family members presented
  symptoms
• Mid-May, epidemic under control
• 19 April, new outbreak spread on 8th floor of
  North York General Hospital
• July 2, WHO removed Toronto from list
• 251 cases diagnosed 43 patients died

Source WHO Update 93
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Singapore

• Index case was 23-year-old woman of Chinese
  ethnicity
• Virus spread rapidly
• April 20, market closed for 15 days
• 76 infections acquired in a healthcare facility
  
• 238 cases diagnosed 33 patients died
• May 31, Singapore removed from list

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Probable cases of SARS, by reported source of
infection
Source MMWR 52 405-11
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China

• 37 cases reported by April 19
• More than 400 new SARS cases
• April 23, the WHO extended SARS-related travel
  advice
• Epidemic seems under control
• 5,327 cases diagnosed 349 patients died
• June 24, Beijing removed from list

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Taiwan

• On March 14, first two suspected
• SARS cases diagnosed
• Last of April, SARS increase steadily
• Third-worst epidemic in the world
• Potentially exposed persons estimated
• 10,000 patients and visitors 930 staff
• July 5,Taiwan removed from list

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Reported Number of Probable SARS Cases
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Reported Number of Probable SARS Cases (Continued)
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Reported Number of Probable SARS Cases (Continued)
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Eradication

• Availability of a vaccine
• Easy-to-use diagnostic tools needed
• Infection of humans must be essential to the
  life-cycle of the causative agent
• To achieve eradication, control intervention must
  be safe, simple, and affordable

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Outlook

• Lessons learned
• One individual required for outbreak
• SARS virus transmissible to cause a very large
  epidemic if unchecked
• Unsuspected SARS patients will be greatest
  challenge in medicine if SARS cannot be
  eradicated
• Many questions remain unsolved