国立感染症研究所

 logo40

The Topic of This Month Vol. 34, No. 5 (No. 399)


Enterohemorrhagic Escherichia coli infection in Japan as of April 2013
(IASR 34: 123-124, May 2013)

 

Enterohemorrhagic Escherichia coli (EHEC) infection is a category III notifiable infectious disease in the National Epidemiological Surveillance of Infectious Diseases (NESID) under the Law Concerning the Prevention of Infectious Diseases and Medical Care for Patients of Infections (Infectious Diseases Control Law).  All the cases must be notified by a physician who has made the diagnosis (http://www.niid.go.jp/niid/en/iasr-sp/2251-related-articles/related-articles-399/3534-de3991.html).  When an EHEC infection is notified as food poisoning by physicians or judged as such by the director of the health center, the local government investigates the incident and submits the report to the Ministry of Health, Labour and Welfare (MHLW) in compliance with the Food Sanitation Law.  Accordingly, there are two related but independent systems of notification, the one in compliance with the Infectious Diseases Control Law and the other in compliance with the Food Sanitation Law.

Prefectural and municipal public health institutes (PHIs) conduct isolation of EHEC, serotyping, and verotoxin (VT) typing and report the result to Infectious Disease Surveillance Center (IDSC) in National Institute of Infectious Diseases (NIID).  The Department of Bacteriology I, NIID conducts molecular epidemiological analysis, whose result is made available through the PulseNet Japan (see p. 139 of this issue). 

Cases notified under NESID:  In 2012 (January-December), total 3,768 EHEC infections, 2,362 symptomatic and 1,406 asymptomatic, were reported (Table 1).  Asymptomatic infections are detected during the active surveillance of outbreaks or regular stool test of cooks.  As in previous years, a large peak of epidemics occurred in summer (see weekly reports summarized in Fig. 1).  The incidence (cases per 100,000 population) was highest in Saga Prefecture (9.21) followed by Okayama (8.71) and Iwate Prefecture (8.14) (Fig. 2, left).  As in previous years, incidence of EHEC infection was highest among the age group of 0-4 years followed by 5-9 year age group (Fig. 3).  When prefectures were compared for the EHEC incidence (cases per 100,000 population) among 0-4 year age group, Okayama, Kagoshima and Miyazaki Prefectures were the highest (Fig. 2, right).  Symptomatic cases were relatively high in young and aged groups and relatively low in population in their 30’s, 40’s and 50’s (Fig. 3).  Total 94 hemolytic uremic syndrome (HUS) cases, corresponding to 4.0% of symptomatic cases, were reported in 2012 (see p. 140 of this issue).  Among 94 HUS cases, EHEC were isolated from 70 cases (the remaining 24 cases were EHEC isolation negative but LPS antibody positive or VT positive).  Among the 70 cases, there were 58 O157, four O111, two O26, two O145 and one each for O25, O165, O174 and O183.  Sixty-six isolates among 70 were positive for VT2 or VT1&2 (94%).  Fifteen fatal cases were reported, among which three were HUS and two EHEC-related encephalopathy. 

EHEC isolated in PHIs:  In 2012, number of EHEC isolates that PHIs reported to the IDSC, NIID, was 1,957, which was far less than the reported number of EHEC infection cases, 3,768 (Table 1).  This discrepancy is due to the current situation where isolates in clinical or commercial settings are not always sent to PHIs.  The most frequent O-serogroup was O157 (53%), followed by O26 (27%) and O103 (5.2%) (see Table on p. 125 of this issue).  Among the O157 isolates double positives for VT1 and VT2 genes were predominant (68%) as in previous years (53-78% in 1997-2011).  Among O26 and O103, 94% and 97%, respectively, were single positive for VT1.  Information on clinical symptoms were available for 973 cases among 1,040 cases of O157.  Major symptoms were abdominal pain (64% of the cases), diarrhea (62%), bloody diarrhea (46%), and fever (21%) (see Table on p. 125 of this issue).

Outbreaks:  In 2012, PHIs reported to IDSC twenty-three EHEC outbreaks, including six outbreaks caused by O157.  Sixteen outbreaks involving ten or more EHEC-positive cases are shown in Table 2.  Five outbreaks were suspected to be food-borne, and ten were suspected for person-to-person transmission.  In 2012, prefectures reported 17 EHEC incidents with 398 symptomatic patients (isolation negative cases included) in compliance with the Food Sanitation Law (25 incidents and 714 patients in 2011).

In 2012, there was an EHEC O157 outbreak caused by lightly pickled vegetables (see pp. 126 & 127 of this issue).  The outbreak mainly affected an elderly facility in Sapporo City, but as the product was distributed to supermarkets, hotels and restaurants as many as 169 persons fell ill and eight died.

Prevention an measures to be implemented:  The basics for preventing EHEC infections are to observe the principles of food poisoning prevention and to avoid consumption of raw or undercooked beef.  In response to persistent food poisonings caused by raw beef, MHLW revised the standards of the beef marketed for eating raw and put it into operation by issuing the MHLW notice No. 321 on October 2011.  Further, upon the detection of EHEC O157 in the inner part of cattle livers, MHLW banned marketing of the cattle liver for eating raw (notice No. 404 in July 2012).  As a consequence, the incidence of O157 cases related to consumption of raw beef or raw cattle liver significantly decreased in one year from 2011 to 2012 (see p. 129 of this issue). 

In response to O157 outbreaks caused by pickled vegetables, MHLW modified the hygiene standards of pickled vegetables (Shoku-An-Kan-Hatsu 1012 No.1, 12 October 2012) (see p. 128 of this issue).

Like dysentery bacilli, EHEC establishes infection even at minute doses and can spread from person to person rather easily.  The year 2012 experienced several EHEC outbreaks in nursery schools (Table 2).  Preventing such outbreaks needs appropriate hygienic practice, such as routine hand washing and sanitary use of children’s padding pools during summer (see “Infection Control Guidelines for Nurseries” revised in November 2012 that recommends confirmation of appropriate concentration of chloride ions and disinfection of water used for swimming baths).

To prevent spread of EHEC within patients’ families, the health center should give full instructions to the families concerning prevention of secondary infections.

Update 2013 :  In 1-15 weeks of 2013, 188 EHEC infections have been reported (Table 1).  As EHEC infection increases in summer season, increased level of vigilance is necessary.

 
 

Copyright 1998 National Institute of Infectious Diseases, Japan

Top Desktop version