Jpn. J. Infect. Dis., 59, 2006

Laboratory and Epidemiology Communications

A Cluster of Hepatitis E Virus Infection in Hokkaido, Japan
Setsuko Ishida*, Shima Yoshizumi, Masahiro Miyoshi, Toyo Okui, Akira Ishida1,Syoji Abe1, Hiroshi Otsuka1, Motohiko Okano and Masaichi Yonekawa
Hokkaido Institute of Public Health, Sapporo 060-0819 and 1Kitami Health Center, Kitami 090-8518, Japan
Communicated by Tatsuo Miyamura(Accepted February 3, 2006)
Table 1. Detection of hepatitis E virus RNA and the presence ofantibodies in individuals tested

On November 16, 2004, the Kitami Health Center (KHC)of Hokkaido, Japan, was notified of a case of hepatitis E in a
69-year-old man who had shown symptoms of diarrhea andfever in the middle of September. He deteriorated rapidly anddied of fulminant hepatitis on October 14. A retrospective
survey revealed that the patient and his family members
had visited a barbecue restaurant on August 14. The survey
further revealed that total of 388 individuals visited therestaurant on the same day and might have eaten barbecued
meat such as beef, pork, chicken as well as various organsof these animals. Because the case described here was also
reported in the news media, an unrelated customer who
visited the same restaurant on the same day and subsequently
developed hepatitis-like symptoms consulted the staff of theKHC about a potential hepatitis E virus (HEV) infection.
In total, the initial patient and 13 of his family members(termed Group A), the unrelated customer and 7 of his family
members (Group B), and 5 employees of the restaurant (GroupC), were examined to see whether they had HEV infections.
Virological studies using nested reverse transcriptasepolymerase chain reaction (RT-PCR) showed that only one
serum sample (obtained from one of the family members) of
the 26 sera and 12 stool specimens taken from Group A
was positive for HEV G4 RNA (Table 1). PCR was carriedout using HEV-F1/HEV-R2 and HE044/HE040 as first PCRprimers and HEV-F2/HEV-R1 and HE044/HE041 as second
PCR primers (1). However, the serum of the index patient,which was available only in a sample which had been taken
after approximately 3 weeks of illness, did not show any traceof HEV RNA. HEV RNA was also negative in the 8 sera and8 stool specimens from Group B, and the 5 sera and 2 stool
specimens from Group C. The nucleotide sequence of thePCR product from the only positive sample was most closely
related to that of JSM-Sap 95 (AB1617171.1) (2).
Since meats and organs were not stored at the restaurant,
30 different samples of pork liver were collected from theregional wholesaler and were tested for the presence of HEV
RNA by nested RT-PCR. Real-time PCR was also performed
using a HECOM-S/HECOM-AS primer set and a TP-HECOM
probe. All samples tested were negative for HEV RNA.
Three different sera from Group A including that of theindex patient and a serum from a family member of the unrelated customer of Group B were found to be positive foranti-HEV IgM antibody by enzyme-linked immunosorbent
assay (ELISA) (3), however, these antibodies were not detectedin the serum of the Group A patient whose serum was positivefor HEV RNA. A serum sample from the unrelated customer
was negative for anti-HEV IgM antibodies even though hewas symptomatic. All patients whose sera were positive foranti-HEV IgM antibodies were also positive for anti-HEV
IgG antibodies. Additionally, 5 individuals from Group A, 3from Group B and 1 from Group C were positive for only
anti-HEV IgG antibodies, suggesting that they had previously
had HEV infections.
Initially, food items were suspected as the source of infection in these cases because of the occurrence of primary
infection in two different tested groups. However, we wereunable to confirm this possibility without further information
about the stored materials. No other food that all subjects had
eaten was identified.
In summary, 4 individuals in Group A, including the initial
patient, and 1 in Group B were considered to be infected withHEV due to the detection of HEV RNA and/or the presenceof anti-HEV IgM antibodies. HEV infection is generally
subclinical during approximately 6 weeks following primary
infection even in individuals who develop the illness (4). Most
HEV-infected cases recover spontaneously without developing obvious hepatitis or even any symptoms. The period inwhich it is possible to detect the viral gene from clinical specimens is limited to the acute phase. Therefore, it is generally
difficult to identify the source of infection or trace the routeof infection.
It is important to obtain detailed epidemiological data inorder to be able to distinguish cluster cases from sporadic
ones. It is essential to develop more sensitive and specificmethods of confirming HEV infection in suspected cases.

*Corresponding author: Mailing address: Department of Microbiology, Hokkaido Institute of Public Health, North 19, West12, Kita-ku, Sapporo 060-0819, Japan. Tel: +81-11-747-2711,Fax: +81-11-747-2757, E-mail: ishidas@iph.pref.hokkaido.jp

We would like to thank Dr. Naokazu Takeda, the National
Institute of Infectious Diseases, Tokyo, for anti-HEV antibody detection.
This article appeared in the Infectious Agents Surveillance

Detection of antibody
positive forpositive foranti-HEV IgM anti-HEV IgGGroupNo. of people
examined

Detection ofHEV RNA

A1)
B2)
C3)

1485100310841

Total

2714131): Patient and his family members.
2): Unrelated customer who consulted with and his family members.
3): Employees of the restaurant.

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Report (IASR), vol. 26, 266-267, 2005 in Japanese.

related 7.5-year-apart isolates from Sapporo, Japan.
Hepatol. Res., 29, 212-215.
3. Li, T. C., Zhang, J., Shinzawa, H., Ishibashi, M., Sata,M., Mast, E. E., Kim, K., Miyamura, T. and Takeda, N.
(2000): Empty virus-like particle-based enzyme-linked
immunosorbent assay for antibodies to hepatitis E virus.
J. Med. Virol., 62, 327-333.
4. Lemon, S. M. (1995): Hepatitis E virus. p. 59-75. In
Mandell, G. L., Bennett, J. E. and Dolin, R. (ed.), Principles and Practice of Infectious Disease. 4th ed. New
York, Churchill Livingstone.

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