Professor of Clinical Medicine Koya Ariyoshi

Speciality / Research theme / Keywords
Clinical Tropical Medicine, Clinical Medicine, Clinical Epidemiology
Masters ProgrammeDoctoral Programme


M.D.(Japan), DTM&H (London), MSc Clinical Tropical Medicine (London), PhD (U.K.)

Personal/work Web page addresses





  • Department of Clinical Medicine, Institute of Tropical Medicine (NEKKEN)
  • Department of Infectious Diseases, Nagasaki University Hospital
  • School of Tropical Medicine and Global Health, Nagasaki University
  • Honorary Professor, Clinical Research Department, Faculty of Infectious Tropical Medicine, London School of Tropical Medicine and Hygiene, UK


I had my residency training in internal medicine in Tokyo, 1986-1988. From those days I was interested in working in Africa, which let me do DTMH in London, followed by a post-graduate clinical training in Harare Central Hospital, Zimbabwe, 1989 where I encountered my life work, AIDS. My master project on HIV viral load at LSHTM in 1990 was very successful that I was offered a job as a clinical research fellow at the Jefferiss Wing, St. Mary’s Hospital. My asset of multi-disciplinary human-network has been established when working in London, Oxford and West Africa for 8 years as well as in Tokyo at NIID for 3 years and in Thailand for JICA for 4 years.


I am the course director of Master of Tropical Medicine (MTM) where I teach clinical tropical medicine, malaria and non-malaria febrile illness, STD and HIV/AIDS. I also facilitate the tropical infectious disease case discussion.

As a chief of NEKKEN training/education center, I also organize the three-month diploma course of tropical medicine.


HIV research had been a core of my carrier before joining NEKKEN. It broadened my skills to understand a disease from multidisciplinary aspects such as behavioral, epidemiological, clinical science, molecular immunology and virology. Most of my work has derived from clinical-epidemiology settings such as cohort or case-control studies. I enjoy digging out clinical research questions by seeing patients and discussing with medical professionals. On joining to the current group of NEKKEN, my research topic has been broaden toward pneumonia in low, middle and high-income countries, non-malarial febrile illness such as typhus, leptospirosis. Now we have on-going studies in infectious disease wards in North Vietnam, the Philippines and Japan.

ariyoshi_koya_document01Discussing in an overcrowded ward in Bac Mai Hospital, Vietnam with Dr. Thuy, one of the most experienced I.D. physicians.

The country/countries where you work currently

  • The Philippines
  • Vietnam
  • Thailand
  • Japan

Five MOST IMPORTANT/INTERESTING recent publications

  1. Saito N, Solante RM, Guzman FD, Telan EO, Umipig DV, Calayo JP, Frayco CH, Lazaro JC, Ribo MR, Dimapilis AQ, Dimapilis VO, Villanueva AM, Mauhay JL, Suzuki M, Yasunami M, Koizumi N, Kitashoji E, Sakashita K, Yasuda I, Nishiyama A, Smith C, Ariyoshi K, Parry CM. A prospective observational study of community-acquired bacterial bloodstream infections in Metro Manila, the Philippines. PLOS Neglected Tropical. 2022; 16(5):e0010414.
  2. Dhoubhadel BG, Suzuki M, Ishifuji T, Yaegashi M, Asoh N, Ishida M, Hamaguchi S, Aoshima M, Yasunami M, Ariyoshi K, Morimoto K. High prevalence of multiple serotypes of pneumococci in patients with pneumonia and their associated risk factors. Thorax. 2022; 77(11):1121-1130.
  3. Katoh S, Cuong NC, Hamaguchi S, Thuy PT, Cuong DD, Anh LK, Anh NTH, Anh DD, Sando E, Suzuki M, Fujita H, Yasunami M, Yoshihara K, Yoshida LM, Paris DH, Ariyoshi K. Challenges in diagnosing scrub typhus among hospitalized patients with undifferentiated fever at a national tertiary hospital in northern Vietnam. PLOS Neglected Tropical Diseases. 2019; 13(12):e0007928.
  4. Yanagisawa K, Wichukchinda N, Tsuchiya N, Yasunami M, Rojanawiwat A, Tanaka H, Saji H, Ogawa Y, Handa H, Pathipvanich P, Ariyoshi K, Sawanpanyalert P. Deficiency of mannose-binding lectin is a risk of Pneumocystis jirovecii pneumonia in a natural history cohort of people living with HIV/AIDS in Northern Thailand. PLoS One. 2020; 15(12): e0242438.
  5.  Yamashita Y, Oe T, Kawakami K, Osada-Oka M, Ozeki Y, Terahara K, Yasuda I, Edwards T, Tanaka T, Tsunetsugu-Yokota Y, Matsumoto S, Ariyoshi K. CD4+ T Responses Other Than Th1 Type Are Preferentially Induced by Latency-Associated Antigens in the State of Latent Mycobacterium tuberculosis Infection.  Frontiers in Immunology. 2019; 10:2807.

Link to other publications



My asset is a human-network developed while working as a AIDS-researcher and a clinician in the UK MRC Laboratories, The Gambia, West Africa for 6 years. I then spent 4 years in Thailand for a JICA-project on HIV/AIDS; since becoming a professor of Nagasaki University, developed various clinical-epidemiology research projects in Vietnam, the Philippines and Japan; also have a role in the infectious disease ward at the University Hospital. Head of center for training/education, NEKKEN; Deputy Dean of the School of Tropical Medicine and Global Health. Message for students: ” if you want to make a substantial impact on health in resource-constrained setting, you should work hard.”