Volume 3, Number 2—June 1997
News and Notes
International Conference on Emerging Zoonotic Infectious Diseases, Taipei, Taiwan
The International Conference on Emerging Zoonotic Infectious Diseases, cosponsored by the Taiwan Departments of Health and Defense and the Centers for Disease Control and Prevention, was held March 1-4, 1997 in Taipei, Taiwan. The conference brought together scientists from Australia, France, the United States, and Taiwan and highlighted local work on dengue, Japanese encephalitis, plague, and rodentborne hantaviral infections.
The opening session outlined current efforts in the United States and internationally to improve and coordinate surveillance, laboratory diagnosis, and research of emerging infectious diseases. An example of a disease (yellow fever) whose threat has not been realized was described and reassessed in the context of globalization and other factors favoring and mitigating against the virus' dissemination. Although the possibility of epidemic yellow fever in Asia is small, it is important to reduce the disease at its sources in Africa and South America to further minimize this possibility. Ongoing efforts to elucidate the pathogenesis of dengue hemorrhagic fever, a growing problem in Taiwan and a leading cause of childhood illness and death in Asia and the tropics were summarized. Recent studies in Thai children have defined early clinical immunologic markers that differentiate febrile patients who contract dengue hemorrhagic fever from those with self-limited dengue fever; these findings suggest potential approaches to early recognition and specific intervention.
A session on viral hemorrhagic fevers reviewed recent Ebola virus outbreaks and the discovery of a rapidly growing number of arena-and hantaviruses, their phylogeny and associations, and their specific rodent hosts. The virtual explosion of viruses identified in rodent reservoirs has left studies of their biologic, clinical, and epidemiologic correlates lagging; many of the newly discovered agents are orphan viruses. A report of local rodent surveys showed the presence of several hantaviruses in numerous species in Taiwan; human disease has not been recognized but epidemiologic studies are planned to define the spectrum and incidence of human infection. Approaches toward producing recombinant hantavirus vaccines and efforts to produce naked DNA vaccines for related vectorborne infections were reviewed.
Summaries of the recent emergence of dengue and dengue hemorrhagic fever globally and on Taiwan led to a series of talks on dengue vaccine development. Various approaches were discussed, including candidate live attenuated vaccines, purified inactivated and recombinant subunit antigens, and infectious clone-derived viruses and their engineered chimeras. A similar session focused on Japanese encephalitis (JE), its changing ecology and epidemiology on Taiwan and regionally in Australia, the molecular taxonomy of JE viruses, and recent developments in producing much needed rapid diagnostic kits.
The cellular and molecular basis of JE pathogenesis was addressed in a series of reports on the protective role of bcl-2 in viral-induced apoptotic death, viral inhibitory activity of cell derived NO2, and viral genetic determinants of virulence and attenuation. Alternatives to the only internationally accepted JE vaccine, the relatively reactogenic and expensive inactivated mouse brain-derived vaccine, were discussed, including the live-attenuated SA14-14-2 vaccine produced in China, a Vero cell-derived inactivated vaccine under development in Taiwan, and a chimeric JE vaccine engineered upon a yellow fever 17D virus infectious clone.
The final session concerned plague; it described the history and current status of plague globally and on Taiwan; reviewed new developments in the molecular taxonomy of Yersinia pestis; compared the performance characteristics of various serologic and PCR-based diagnostic tests; and described plague pathogenesis and vaccine development. F1 and V antigens were defined as important virulence factors in mouse and primate parenteral and aerosol challenge models. Preliminary studies indicate their promise as constituents of a recombinant subunit vaccine.