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

Laboratory and Epidemiology Communications

An Influenza AH3 Outbreak in a Hospital, Nara Prefecture, Japan, in Summer 2005
Yasushi Yonezawa*, Yumiko Inoue, Yoshiteru Kitahori and Mamoru Nakano
Virology and Bacteriology Division, Nara Prefectural Institute for Hygiene and Environment, Nara 630-8131, Japan
Communicated by Ichiro Kurane(Accepted December 5, 2005)

An influenza outbreak occurred in summer, a non-epidemic
season, in a hospital in the northern area of Nara Prefecture,
Japan. The outbreak occurred in a ward for mentally andphysically disabled patients. On July 15, the first patient, a43-year-old male inpatient, developed fever (38.7°C) andfatigue of unknown origin. The second patient showed similar
symptoms on July 31, and the disease then spread rapidly
among inpatients and staff members from August 3 toAugust 10. A total of 28 inpatients and 10 staff members
developed a similar illness (Fig. 1). All the patients showed
typical influenza-like symptoms; fever (37.3 to 40.0°C),
dyspnea, cough and rhinorrhea. In the hospital, the patientswere examined with a rapid influenza detection kit using
nasal drips and diagnosed with influenza A virus infection.
To obtain detailed information, we analyzed the virus by
the RT-PCR method, DNA sequencing and hemagglutination
inhibition (HI) assay. Influenza AH3 virus was detected by
the RT-PCR method reported by Shimizu et al. (1), using
specific primers (D01 and D02) for hemagglutinin genes ofinfluenza AH3 virus. Next we determined the sequence of
222 nucleotides after TA cloning (pSTBlue-1 AccepTorTM
Vector Kit; Novagen, Madison, Wis., USA) and compared thesequence with those of influenza AH3 strains in GenBank
using a BLAST search. The results revealed that the detected
A/Nara/29/2005 strain shared a high nucleotide homology
with influenza A/Wyoming/03/2003 (GenBank accession no.
AY531033). Nucleotide and amino acid sequences of thehemagglutinin region are shown in Figures 2A and 2B. Nucleotide and amino acid homologies between these two strains
were 98.7% (227/231 bases) and 97.4% (75/77 amino acids),
respectively. The A/Nara/29/2005 strain had four pointmutations. Three provided amino-acid replacement: 429 (G →Fig. 1. Case distribution of the nosocomial infection.

A, Ala to Thr), 483 (A → C, Lys to Asn) and 524 (A → T, Tyrto Phe), and one was a mutation with no amino acid change(position No. 444). Virus isolation was attempted from six
specimens by inoculating the samples onto MDCK cells. A
cytopathic effect was observed in all of the inoculated cellsby day 3 or 4 after the inoculation. HI assay was performed
using antisera against A/Wyoming/03/2003, A/Kumamoto/102/02 and A/Panama/2007/99, provided by the National
Institute of Infectious Diseases, Tokyo. HI titers against respective antisera were 640 (homotypic titer, 1280), 640 (homotypictiter, 1280) and 20 (homotypic titer, 320). The results suggestthat the isolated A/Nara/29/2005 strain was nearly identicalto A/Wyoming/03/2003, the vaccine strain in the 2004/05
season (2).
In conclusion, the outbreak was caused by influenza AH3virus, which was identified as an A/Wyoming/03/2003-likevirus. This was the main epidemic strain in Nara Prefecturein the 2004/2005 season.
The authors would like to thank Dr. Rika Ishizuka and thestaff members of Koriyama Public Health Center for theircollaboration in this study.
This article appeared in the Infectious Agents Surveillance
Report (IASR), vol. 26 p. 244-245, 2005 in Japanese.

*Corresponding author: Mailing address: Virology and Bacteriology Division, Nara Prefectural Institute for Hygiene and Environment, Ohmori-cho, Nara 630-8131, Japan. Tel: +81-74220-2887, Fax: +81-742-27-0634, E-mail: y.yonezawa@ihe.pref.
nara.jp62

Fig. 2. Nucleotide (A) and predicted amino acid (B) sequences of the A/Nara/29/2005 gene (343-564).

2. National Institute of Infectious Diseases and Tuberculosis
and Infectious Diseases Control Division, Ministry ofHealth, Labour and Welfare (2004): 2003/04 influenza
season, Japan. Infect. Agents Surveillance Rep., 25, 278’279’.

REFERENCES
1. Shimizu, H., Watanabe, S. and Imai, M. (1997): Rapid
detection of influenza virus A (AH1, AH3) and B bynested-polymerase chain reaction. J. Jpn. Assoc. Infect.
Dis., 71, 522-526 (in Japanese).

63