Jpn. J. Infect. Dis., 58, 2005

Laboratory and Epidemiology Communications

Norovirus Outbreaks at Nursing Homes in Osaka, Japan
Naomi Sakon*, Kenji Yamazaki, Tomoko Yoda, Masashi Kanki,Kazuo Takahashi, Teizo Tsukamoto and Toru Otake
Department of Infectious Diseases, Osaka Prefectural Institute of Public Health, Osaka 537-0025, Japan
Communicated by Tatsuo Miyamura(Accepted June 16, 2005)
An epidemic outbreak of norovirus (NoV) raged throughnursing homes in Japan in the past winter season (January,2005). Twenty-five outbreaks of confirmed NoV in nursinghomes and hospitals were involved, together with 13 outbreaks in other facilities. In the present report, we describe
three separate outbreaks that occurred in nursing homes inOsaka, Japan.
Case 1
Between the 15th and 16th of December 2004, two
residents in a nursing home in Daito City showed symptoms
of gastroenteritis including vomiting and fever, and werediagnosed with viral gastroenteritis in a hospital; five otherresidents had similar symptoms. NoV infection was suspected(A)to have been spread by person-to-person contact and was notconsidered to be foodborne because there was no common
source of food. On the 22nd of December, four stool samples
were tested. NoV (GII.4; CAW type) was detected in all
samples by reverse transcriptase-polymerase chain reaction(RT-PCR) using G2F1/G2SKR primers and Yuri primers (1,2).
In total, 39 residents had symptoms; 2 of 28 residents on thesecond floor, 16 of 35 residents on the third floor, 14 of 35
residents on the fourth floor, and one short-term resident on
the first floor. Additionally, 6 staff members, including one
cook had symptoms of gastroenteritis (Fig. 1A). Most of
those infected were located on the third and fourth floors.
Residents of the third floor had senile dementia, residents of

9

staff
residents (short term)
residents 4th floor
residents 3rd floor
residents 2nd floor

number of cases

8(B)

765
4
3
2
100 (15 Dec)

3616

staff

number of cases

14

residents

12residents (short term)

108
6
4
20(C)

0 (3 Dec)

369

12

1516

staff (day care)user (day care)staff (3rd floor)
residents (3rd floor)
staff (2 and 3rd floor)
staff (2nd floor)
residents (2nd floor)

14

number of cases

181210864200 (24 Dec)

369121518

Day of disease onset

Fig. 1. Cases of gastroenteritis in a nursing home in Osaka by day of onset. (A), number of residents by floor and staff
members in Case 1; (B), number of residents, short-term users and staff members in Case 2; (C), number of residents andstaff members by floor in Case 3.

*Corresponding author: Mailing address: Department of Infectious Diseases, Osaka Prefectural Institute of Public Health, 13-69 Nakamichi, Higashinari-ku, Osaka 537-0025, Japan. Tel:
+81-6-6972-1321, Fax: +81-6-6972-2393, E-mail: nsakon@
iph.pref.osaka.jp254

Jpn. J. Infect. Dis., 58, 2005
dents living on the second floor showed signs of diarrhea
between the 26th and 28th of December, though theirsymptoms improved under medical treatment. On the 29thof December, 9 residents and 2 staff members on the second
floor and 3 nurses on the second and third floors became ill(Fig. 1C). Eight fecal samples and 4 vomitus samples wereexamined for NoV on the 4th of January 2005, and NoV GII.4
was detected in all 8 fecal samples and in 2 of the vomitus
samples. In total, 77 people were infected, and the cause wassuspected to be NoV.
There are many kinds of nursing facilities for elderly people
in Japan, depending on their level of mental and physicalability. Their health depends greatly on management decisions and hygiene programs. Therefore, better awareness ofNoV infections should be encouraged to prevent and control
future outbreaks in such closed institutions with high-riskpeople.

fourth floor were self-supporting and did not require muchcare, and residents on the second floor required a high levelof nursing. This outbreak indicates the difficulty of controlling sanitation in communal life for the elderly and people
with dementia. On the other hand, it was possible to prevent
NoV transmission among people confined to bed through theefforts of the staff. It is important to note that the short-term
resident visited all floors of the nursing home. Furthermore,
there is a high risk of spreading NoV in nursing homes fromoutside.
Case 2
At a nursing home in Ibaragi City, in the northern part ofOsaka, one short-term resident vomited in a meeting placeon the 3rd of December 2004. After 2 days one other resident
and 2 staff members became ill. On the 6th of December, 6residents (5 on the first floor and one on the second floor)
and 3 staff members showed symptoms of gastroenteritis. Twopeaks were observed on the 8th and 13th of December (Fig.
1B). At the time of the second peak, a disinfectant was changed
to hypochlorous acid because the possibility of NoV infection
was high. Three stool samples were tested in our laboratoryon the 22nd of December and NoV GII.4 (Bristol, CAW type)was detected in all three. The total number of people withsymptoms increased to 105. In conclusion, NoV infection had
spread from person-to-person contact in the day care facilities
and group home. It was suspected that the vomitus was theinitial source of NoV transmission.
Case 3On the 24th of December, one staff member working ata nursing home in Izumiotsu City showed symptoms ofgastroenteritis, including diarrhea and vomiting. Five resi-This article appeared in the Infectious Agents Surveillance
Report, vol. 26, no. 4, p. 98-100, 2005 in Japanese.
REFERENCES
1. Kageyama, T., Shinohara, M., Uchida, K., Fukushi, S.,
Hoshino, F., Kojima, S., Takai, R., Oka, T., Takeda, N.
and Katayama, K. (2004): Coexistence of multiple genotypes, including newly identified genotypes, in outbreaksof gastroenteritis due to Norovirus in Japan. J. Clin.
Microbiol., 42, 2988-2995.
2. Katayama, K. (2004): Norovirus infection. Infect. Dis.
Wkly. Rep., no. 11, 14-19 (in Japanese).

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