This Department has been conducting basic and applied research on mosquito‐borne flaviviral diseases such as Japanese encephalitis （JE）, dengue fever （DF）/dengue hemorrhagic fever （DHF）, as well as hepatitis C.

Outbreak investigations on mosquito‐borne flaviviral diseases
　　Requested by Japan International Cooperation Agency（JICA）, outbreak investigation was conducted on the acute encephalitis which was caused by Nipah virus in Malaysia from September １９９８ to March １９９９． Another investigation was carried out, requested by the Ministry of Health and Welfare, on the West Nile virus encephalitis occurred in New York during the summer in １９９９．
Analysis on the structure and function of JE and dengue viral genome
　　Nucleotide sequence analysis and molecular expression of JE and dengue viral genome have been carried out together with long PCR techniques in order to study molecular epidemiology, epitope analysis, biological activity of nonstructural proteins, and virulent viral gene responsible for viral pathogenesis.

Development of rapid diagnosis on flaviviral diseases
　　Viral genome detection and identification by PCR, preparation of diagnostic antigen
from infected cell culture fluid, and simplification of IgM antibody detection have been carried out.

Activities as a WHO Collaborating Centre
　By the letter from Dr. San Tae Han, fromer Director of WHO Regional Office for the Western Pacific （WPRO)　dated ２３ November １９９３， the Department of Virology, Institute of Tropical Medicine, Nagasaki University was designated as WHO Collaborating Centre for Reference and Research on Tropical Viral Diseases. On ９ August １９９４， Inauguration Ceremony was held at Pompe Hall by the presence of Dr. Han and approximately １２０ guests, which was followed by the WHO Workshop“Epidemiology and Control on DF/DHF and JE”. The Department has received WHO fellows from Vietnam. Fiji, and the Philippines, dispatching WHO short‐term consultants on the subjects relevant to its terms of reference. Dr.Kouich Morita was appointed as the Regional Advisor on Infectious Diseases, WHO‐WPRO, from １６ May １９９５ to １５ May １９９８． According to the letter from Dr. Shigeru Omi, present Director of WHO‐WPRO, the designation of Virology Department as the WHO Collaborating Centre was extended to ２３ September ２００３．