Molecular Epidemiology of Infectious Diseases-Division of Molecular Epidemiology
Associate Professor: Toyoko Nakagomi, M.D., Ph.D. (female)

Project I. Epidemiology of rotavirus infection in infants and possible association of rotavirus infection with intusussception.
  The strongest impact that my research has made in the history of combating rotavirus infection is undoubtedly our earlier report suggesting that rotavirus is a cause of intussusception (Konno, T., Suzuki, H., Kutsuzawa, T., Imai, A., Katsushima, N., Sakamoto, M., Kitaoka, S.: Human rotavirus and intussusception. New England Journal of Medicine, 297, 945, 1977). While subsequent studies failed to replicate our observations, the first licensed rotavirus vaccine, Rotashield, caused intussusception in its recipients and thus was pulled off from the market. Therefore, there is still a good possibility that some strains, among the myriads of human and animal rotaviruses, may cause intussusception upon infection. The major safety concern of live attenuated rotavirus vaccines is, therefore, whether such vaccines may trigger intussusception in their recipients. In this regard, the information regarding the baseline incidence of idiopathic intussusception in children is critically important, particularly in infants, because it is suspected that the incidence of intussusception varies from period to period and in different geographic locations.
  1. Nakagomi, T. Rotavirus infection and intussusception: a view from retrospect. Microbiology and Immunology 44, 619-628, 2000.
  2. Nakagomi, T. Intussusception and an oral rotavirus vaccine. New England Journal of Medicine, 344: 1866, 2001
  3. Nakagomi, T., Takahashi, Y., Arisawa, K., Nakagomi, O. A high incidence of intussusception in Japan as studied in a sentinel hospital over a 25-year period (1978-2002). Epidemiology and Infection (in press).
Project II. Antigenemia in the acute phase of rotavirus infection.
  A potentially important that is concern currently emerging and merits careful evaluation is whether rotavirus commonly causes viremia and, if so, if vaccine strains share the same characteristics. Rotavirus is generally considered to cause a disease that is limited to the gastrointestinal tract. However, there have been sporadic reports in the literature of extra-intestinal rotavirus infection principally involving the central nervous system, but also affecting the blood, liver and spleen. A recent report documenting the presence of rotavirus antigen in the blood of rotavirus-infected animals, and in 67% of serum samples from otherwise healthy children with rotavirus diarrhea, suggests that rotavirus infection of the blood may be more common than previously imagined. While the clinical significance of these findings is uncertain, it does raise the theoretical concern that current rotavirus vaccines, comprising live, attenuated virus particles, could also escape beyond the intestinal tract.
  1. Nakagomi T, Nakagomi O. Rotavirus antigenemia in children with encephalopathy accompanied by rotavirus gastroenteritis. (submitted for publication)
Project III. Epidemiology of rotavirus infection in an attempt to obtain an estimate of the incidence and the burden of rotavirus disease in Japan.
  The development of preventive measures, including vaccines, against rotavirus disease requires an objective analysis of its impact. Accurate estimates of the incidence and the burden of rotavirus disease are lacking in Japan. In addition, we address the question of how rotavirus infection in adults is related to rotavirus infection in children.
  1. Nakagomi O, Koshimura Y, Nakagomi T: Rotavirus vaccine in Japan and Australia. Lancet 353: 1275, 1999.
  2. Nakajima H, Nakagomi T, Kamisawa T, et al.: Winter seasonality and rotavirus diarrhea in adults. Lancet 357: 1950, 2001
  3. Nakagomi T, Nakagomi O, Takahashi Y, Enoki M, Suzuki T, Kilgore PE. The incidence and burden of rotavirus gastroenteritis in Japan as estimated from a prospective sentinel hospital study. Journal of Infectious Diseases (in press).