The South to North Variation of Norovirus Epidemics from 2006–07 to 2008–09 in Japan

Abstract

The decrease of the number of sentinel cases at the peak week may suggest the development of herd immunity after a period of high prevalence. Although the NoV epidemic is thought to be associated with cold weather, its cases first increased in the southern area with relatively warm temperature, indicating there are other climate factors involved. Geographic study using the sentinel data could enhance the monitoring and surveillance of and preparedness against epidemics.