PART V: Discussion

1. PART V: Discussion

2. Factors leading to the emergence of infectious diseases Changes in society, technology, environment and microorganisms are leading to increases in host susceptibility and/or disease transmission and the evolution of new or drug-resistant microorganisms

3. Candidate Factors AffectingEmergence of SARS • Human demographics and behavior • Human susceptibility to infection • Economic development and land use • Changing ecosystems • International travel and commerce • Microbial adaptation and change • Breakdown of public health measures • To be determined . . . IOM: Microbial Threats to Health: Emergence, Detection, and Response. March 2003.

4. Infectivity • Infectivity is the ability of a virus to jump from one person to another • The recipient must receive a dose large enough to cause the disease • From epidemic reports, it appears that SARS virus has low infectivity (ie it requires a large dose to pass on to the recipient) • Other members of the coronavirus family have very high infectivity.

5. Virulence • Virulence is the property of the virus to cause damage to the patient’s organs • The SARS virus is very virulent • Other members of the coronavirus family have low virulence.

6. Attenuation • Attenuation is a phenomenon seen in some members of the coronavirus family, where the virulence decreases when it jumps from person to person. • Initial decrease in cases suggested attenuation • Enough information is still not available to suggest this phenomenon in the current SARS outbreak • Recent clusters suggest that the virus might be getting more virulent

7. Seasonal incidence of coronavirus infections Disease is now in the Spring season?

8. Research in China • Organ samples of 7 fatal cases of SARS • 293 cell line inoculated from materials derived from lung to isolated the agent(s) • Agents in organs and cell cultures revealed by immunoassay • Result • Chlamydia-like & Coronavirus-like particles found on EM • Chlamydia-like agent visualized in both organs and cells • Were non-reactive with • genus-specific antibodies against Chlamydia • monoclonal antibodies against chlamydia pneumoniae and c. psittaci • Results consistent with a novel chlamydia-like agent Source: Hong T. et al. Chlamydia-like and coronavirus-like agents found in dead cases of atypical pneumonia by electron microscopy. National Medical Journal China 2003;83:632-6

9. Addressing the Threat of SARS • Enhancing global response capacity • Improving global infectious disease surveillance • Rebuilding domestic public health capacity • Developing diagnostics • Educating and training multidisciplinary workforce • Vaccine development and production • Need for new antimicrobial drugs IOM: Microbial Threats to Health: Emergence, Detection, and Response. March 2003.

10. Future course of outbreak Source of virus Mode of transmission in community Risk of household transmission Risk of transmission on airplanes and ships Environmental persistence/decontamination Period of infectiousness Explanation for age distribution Importance of “hypertransmitters” Role of co-infection Optimal diagnostic test(s) Effective therapy Vaccine approaches Unanswered Questions?

11. Thank you!!!!!!