Presentation on theme: "Outbreak Investigation Severe Acute Respiratory Syndrome SARS April 2003."— Presentation transcript:
Outbreak Investigation Severe Acute Respiratory Syndrome SARS April 2003
Field Investigation Determine the existence of an outbreak Confirm the diagnosis Define a case and case counts Orient data in terms of time, place and person Determine who is at risk Develop hypothesis Compare hypothesis with established facts Written reports and communications Execute control and prevention
Determine the existence of an outbreak Feb 11, 2003 … Chinese MOH informed WHO of 305 cases of acute respiratory disease in Guangdong between Nov 16, 2002 and Feb 9, 2003 – details sparse, etiology unknown Late February, outbreak of respiratory disease among health care workers in the Prince of Wales hospital (Hospital 1) in Hong Kong – influenza ruled out
Determine the existence of an outbreak March 5 health care workers in Hanoi hospital present with respiratory illness of unknown etiology – total of 59 persons WHO issues a global alert on March 12 th, 2003
Case Definition – CDC March 19, 2003 Respiratory illness of unknown etiology with onset since February 1, 2003 Documented fever greater than 38C (100.4F) One or more symptoms of respiratory illness (e.g. cough, shortness of breath, difficulty breathing, radiographic findings of pneumonia or ARDS Close contact within 10 days of onset with a person with SARS or travel to an area with documented transmission as defined by the WHO
Case Definition – CDC March 22, 2003 Respiratory illness of unknown etiology with onset since February 1, 2003 Documented fever greater than 38C (100.4F) One or more symptoms of respiratory illness (e.g. cough, shortness of breath, difficulty breathing, radiographic findings of pneumonia or ARDS Close contact within 10 days of onset with a person with SARS Travel to an area with documented transmission as defined by the WHO, excluding areas with secondary cases limited to hcw or direct household contacts
Case Definition – CDC March 28, 2003 Respiratory illness of unknown etiology with onset since November 1, 2002 Documented fever greater than 38C (100.4F) One or more symptoms of respiratory illness (e.g. cough, shortness of breath, difficulty breathing, radiographic findings of pneumonia or ARDS Close contact within 10 days of onset with a person with SARS Travel to an area with documented transmission as defined by the WHO, excluding areas with secondary cases limited to hcw or direct household contacts. This now includes the whole of China
Orient data in terms of time, place and person - Index case Index case (patient A) Travelled to Hong Kong from Guangdong Province Onset of symptoms on February 15, 2003 Travelled to Hong Kong to visit family Stayed at the Metropole Hotel Feb 21 Was admitted to hospital 2 Feb 22 Died on Feb 23
Orient data in terms of time, place and person Feb 26, 2003 recent traveller to China and Hong Kong (Patient B) became ill in Hanoi, Vietnam. Transferred to the Princess Margaret Hospital in Hong Kong (hospital 4) and died March 13, 2003 Health care workers at the Prince of Wales Hospital (Hospital I) become ill. Patient J appears to be the common contact. Patient was admitted on March 5 and first illness among health care workers was March 7.
Orient data in terms of time, place and person Department of Health in Hong Kong determines a possible link in 5 of the “index” cases – the Metropole Hotel in Hong Kong
Hotel Metropole Patient A stayed at the Metropole on February 21 and was hospitalized the next day 12 other patients were linked to the Metropole –10 were also in the Metropole on February 21 –2 others were there at the same time as 3 others who were symptomatic 9/13, including patient A were on the 9 th floor. 1 was on floor 14, 1 on floor 11 and 2 stayed on both floor 9 and floor 14
Hypothesis Development Reports of outbreaks of Chlamydia pneumoniae in China … is this chlamydia too? Scientists in Hong Kong report finding viruses which look like paramyxoviruses in patients in Hong Kong Scientists unable to find influenza viruses in patients CDC and others report a coronavirus in EM of tissue from cases
Hypothesis Development – clinical picture Rapid onset of high fever Myalgia, chills, rigor and sore throat Shortness of breath, cough, radiographic evidence of pneumonia Leukopenia and thrombocytopenia Mortality rate is about 3% Secondary attack rate of >50% among hcw and close family contacts
Hypothesis Development - Diagnostic work-up Chest radiograph Pulse oximetry Blood cultures Sputum Gram stain and culture Testing for respiratory viruses, especially flu A & B and RSV Clinical specimens should be saved for further testing if necessary
Hypothesis Development - Transmission Appears to be close contact –Secondary cases among family members and health care workers (e.g. Hong Kong) Development of the “super- transmitter” developed to explain why in some situations there is efficient transmission to others and in other situations this is not the case
Compare the hypothesis with established facts Challenge when the etiologic agent is an new pathogen or a more virulent form of a relatively common pathogen Koch’s postulates –1. The specific organism should be shown to be present in all cases of animals suffering from a specific disease but should not be found in healthy animals. –2. The specific microorganism should be isolated from the diseased animal and grown in pure culture on artificial laboratory media. –3. This freshly isolated microorganism, when inoculated into a healthy laboratory animal, should cause the same disease seen in the original animal. –4. The microorganism should be re-isolated in pure culture from the experimental infection.
Investigation into Treatment Reports from Far East that ribavirin and steroids are effective, but this evidence is not substantial Antibiotics are not effective Suggestive of a viral origin
All countries are reporting only probable cases of SARS to WHO Exception is the US which reports suspect cases Among reports to the WHO probable (and suspect) cases have been eliminated as other etiologies are confirmed to explain the clinical syndromes
Written Reports/Communications Hong Kong –Daily press briefings –Letter to all physicians in HK –Instructions for the public to reduce risk of infection WHO –Daily web updates –Coordination of country reports CDC –MMWR articles –Press briefings
Control and Prevention WHO Alert CDC – –Notice to Travellers –Travel recommendations – avoid Hong Kong and China Govt of Ontario –restricted access to hospitals in Ontario –Screening of patients Hong Kong –School closures –Quarantine of apartment block
World travel – 2000 Non-residents passenger arrivals
Impact of Disease (Singapore-Thursday, March 27)--The Rolling Stones announced today that they have cancelled their concerts in Hong Kong on March 28 and March 29 as a result of the warnings on SARS (Severe Acute Respiratory Syndrome) from the Hong Kong Government and the World Health Organization. Increases in the number of cases of SARS in Hong Kong and Southern China and continued concern over large gatherings have created apprehension among fans and concern for their safety. The Stones plan to reschedule the concerts as soon as possible.
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