Jahresbericht - Gesundheitsserver - Land Steiermark

immediately, without waiting for virological confirmation. This report describes a norovirus outbreak confined
to a nursing home and a related hospital, and assesses the control measures undertaken.
Outbreak Background
On November 16, 2004 the Austrian Agency for Health and Food Safety was contacted by a local public health
officer. He reported the occurrence of ongoing clusters of short-living gastro-enteritis in a nursing home and a
nearby hospital. The latter also affected staff members, causing considerable organisational problems at the
afflicted department. The local health authority created an outbreak management team in order to investigate
and to control the two institutional clusters (responsible public health officer, microbiologist, an epidemiologist,
AGES, the head of the nursing staff of the nursing home and the infection control physician of the hospital. The
objectives of the investigation were to assess the extent of the outbreak, the relation between the two
institutional clusters, to identify the route of transmission, the causative pathogen and to evaluate the control
measures undertaken.
Methods
Definitions:
Outbreak case: Cases in the nursing home were defined as persons having been residing or working there and
who presented at least with one of the two symptoms diarrhoea or vomiting between November 9 and 17. Cases
at the hospital were defined as either persons who have been hospitalised at the Internal Medicine Department
due to illnesses other than gastro-intestinal infection or as hospital staff members who have worked at one of the
two wards of the Internal Medicine Department, and who have developed at least one of the two symptoms
diarrhoea or vomiting between November 11 – 28, 2004.
Household secondary case: Household secondary cases were defined as household members of the cases among
the nursing home staff and Department staff who reported diarrhoea or vomiting between 1 to 7 days after the
corresponding cases had fallen ill. This time period equals the time between the minimum and maximum serial
interval between two successive cases of NV infection.
The attack rate for the nursing home and the Department of Internal Medicine of the hospital were calculated
by the number of cases of the nursing home and of the hospital department, respectively, over the susceptible
population exposed.
The staff-household secondary attack rate was defined as the number of household secondary cases over the
total number of household members exposed to cases of the nursing home staff and the department staff.
Epidemiological investigation:
The following information was obtained from all cases: sex, date of birth, date of clinical onset and cessation,
whether they had vomiting, diarrhea or both and contact pattern. Exposure status to food items eaten within 2
days prior to clinical onset was obtained from all cases of the nursing home. The service staff in the nursing
home was asked whether they had suffered from diarrhea or vomiting between 1 and 7 days prior to the
occurrence of the index case. The persons having visited the index case in the 2 days prior to its clinical onset,
were asked whether they had had symptoms of acute gastroenteritis compatible with NV infection within the 5
days prior to the visit of the index case. The time period of 5 days equals the maximum duration of
infectiousness. Cases of the nursing home staff and the department staff were asked whether short-living
gastroenteritis had occurred in their households between 1 day and 7 days after they had fallen ill. The
information was ascertained either in face-to-face interviews or by telephone interviews with the staff, and by
reviewing patients’ charts for ascertaining information on symptoms and duration of illnesses of the cases
among the residents and hospital patients.
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