Surveillance of viral gastroenteritis in Japan: pediatric cases and outbreak incidents

Abstract

Surveillance results from pediatric cases and outbreaks of viral gastroenteritis in Japan are presented. In winter, both small round structured virus (SRSV, or Norwalk-like viruses) and rotavirus were detected from infants with gastroenteritis; however, in recent years, the prevailing time of SRSV infection has preceded that of rotavirus infection. Most nonbacterial gastroenteritis outbreaks were related to SRSV infection, and >60% of the outbreaks were caused by contaminated food. In small-sized outbreaks, raw oysters were the primary source of transmission. In large-sized outbreaks, school lunches and catered meals that were served at schools, banquet halls, and hospitals were most often implicated in the transmission of foodborne gastroenteritis.

Figure 1

Viral gastroenteritis trends in Japan. A, Nos. of gastroenteritis patients per week reported by pediatric sentinel clinics. Nos. of patients clinically diagnosed per week at sentinel clinics are electronically reported to Infectious Disease Surveillance Center (IDSC), National Institute of Infectious Diseases (Tokyo). B, Nos. of patients per week positive for small round structured viruses (SRSV). C, Nos. of group A rotavirus-positive patients per week. Fecal specimens from some patients are sent to prefectural/municipal Public Health Institutes for laboratory diagnosis, and virus-positive results are electronically reported to IDSC.

Figure 2

Occurrence of gastroenteritis by prefecture in Japan during peak of outbreak in 51st week of 1997.

Figure 3

Age (in years) distribution of virus-positive gastroenteritis patients in 1997/1998 season—Japan. SRSV = small round structured viruses.

Figure 4

Nos. of nonbacterial gastroenteritis outbreaks, by month—Japan, 1997 to March 1999. Data are based on reports sent by Public Health Institutes to Infectious Disease Surveillance Center by 11 March 1999. SRSV = small round structured virus; Rota A and C = group A and C rotavirus, respectively; Corona = coronavirus; CA9 = coxsackievirus A9.

Figure 8

Comparison of trends for oyster-associated and -unassociated small round structured virus (SRSV) gastroenteritis outbreaks and trends of pediatric cases with SRSV gastroenteritis in 1997/1998 season—Japan. A, Nos. of SRSV-positive outbreaks per week with or without oyster association. B, Nos. of SRSV-positive pediatric cases per week (from figure 1B).

Figure 5

Size distribution of gastroenteritis outbreaks related to small round structured virus—Japan, 1997 to March 1999. 208 outbreaks with known nos. of patients are classified according to size of outbreak. Data are based on reports sent by Public Health Institutes to Infectious Disease Surveillance Center by 11 March 1999.

Figure 6

Setting for 208 outbreaks of gastroenteritis associated with small round structured viruses—Japan, 1997 to March 1999. Outbreaks are classified into 3 size groups. Data are based on reports sent by Public Health Institutes to Infectious Disease Surveillance Center by 11 March 1999.

Figure 7

Suspected modes of virus transmission and implicated foods in 208 outbreaks of small round structured virus—related gastroenteritis—Japan, 1997 to March 1999. Transmission routes are classified into foodborne, person-to-person, and unknown modes. Data are based on reports sent by Public Health Institutes to Infectious Disease Surveillance Center by 11 March 1999.