Norovirus is considered to be the largest causative agent of non-bacterial acute gastroenteritis, and is known to multiply in the intestinal tract when infecting humans.It is speculated that the existence of "asymptomatic infected persons" who are infected but do not manifest clear symptoms is important as a source of infection for the transmission of norovirus infection, but the actual situation is unknown.

　The research group continuously collected fecal specimens from 2015 asymptomatic healthy volunteers in Indonesia for the year 2016-1 to clarify the mode of transmission of norovirus infection, and the norovirus present in the stool. Epidemiological analysis of the genome was performed.Since Indonesia and Japan are geographically close to each other and have been actively interacting with each other for a long time, it can be said that they are extremely important as a transmission route for infectious diseases.In Japan, an epidemic of norovirus infection is seen in winter, but in Indonesia, which has a subtropical climate, the actual state of the epidemic is hardly known.

　As a result of the analysis, the norovirus genome was detected in 512 out of 14 samples (7 asymptomatic persons), and recombinant norovirus between different genotypes was also detected.In addition, two of the seven asymptomatic individuals had recurrent infections with the same or different strains.From this, it became clear that asymptomatic persons were infected with norovirus at a high rate, and it was suggested that asymptomatic persons are important as an infection source for the norovirus infection epidemic in Indonesia.

　In the future, it will clarify what are the important viral factors and host factors for the conversion from asymptomatic to symptomatic infection, and the impact from Indonesia to Japan.

Paper information:[Infection, Genetics and Evolution] Occurrence of norovirus infection in an asymptomatic population in Indonesia