Norovirus, also called "winter vomiting bug" is the most common cause of acute gastroenteritis in humans. A recent study has identified the significant presence of norovirus in the stools of healthy volunteers in Indonesia who are asymptomatically infected with the virus. The discovery suggests that asymptomatic infection is a major source of norovirus outbreaks.

We already knew that infected asymptomatic people are important in transmitting the norovirus infection, but the details of this process were unclear. When norovirus infects humans it breeds in the intestine, and researchers predicted that the virus spreads by transferring from asymptomatic people to infants and the elderly. In Japan and Europe the norovirus infection spreads during the winter season, but scientists had not investigated how it is transmitted in the subtropical climate of Indonesia.

Our team collected stool samples from healthy volunteers in the city of Surabaya, Indonesia, and performed epidemiological analysis on the norovirus genome in the samples. We collected 512 samples from 18 healthy, asymptomatic volunteers over one year (2015- 2016). Among these samples, 14 (2.7%) tested positive for norovirus. The positive samples all belonged to genogroup GII. After further analysis, norovirus strains composed of recombinant variations of the virus were detected, showing that of the 7 positive individuals, 2 had been repeatedly infected with the same strain or different strains. From these results it is clear that asymptomatic individuals are infected with norovirus at a high rate, and these healthy individuals are an important source of norovirus outbreaks in Indonesia.