Jahresbericht - Gesundheitsserver - Land Steiermark

the index case experienced a severe episode of vomiting while gathering with most of the residents and staff
members in the dining room on November 9. In total, 17 nursing home residents and seven staff members fell
ill with diarrhoea or vomiting between November 10 and 17, following the vomiting episode of the index case.
In 11 of 17 cases of the nursing home residents and 5 of 7 cases of the nursing home staff the median time
between exposure to the vomiting episode of the index case on November 9 and illness was 2 days, which is
consistent with a point source of infection. The remaining eight cases, 6 nursing home residents and 2 staff
members, showed extended time periods from the episode of vomiting of the index case to clinical onset of their
illness. They can not have been generated by the index case due to direct airborne transmission. Person-toperson
transmission or exposure to contaminated environment must have generated these cases.
The index case was hospitalised on November 10 in a hospital situated 5 km apart from the nursing home.
Another 7 cases of the nursing home residents were admitted in that hospital at the same Department
(Department for Internal Medicine), 4 cases on November 11, 1 case on November 14 and 2 cases on November
17. Clinicians and the local public health officer primarily suspected the increased number of hospitalisation at
the Internal Medicine Department to be due to an outbreak of salmonella infections in the nursing home.
Specific hygienic precautions against person-to-person transmission were not considered at the time when the
cases were admitted. Between November 11 - 28, 2004, ten of the 46 hospital patients at the Internal Medicine
Department (22%) and 18 persons of the 60 staff members having been on duty at the Internal Medicine
Department (30%) fell ill with vomiting or diarrhoea (Figure 3). Interviews with the department staff revealed
that direct contacts have occurred between cases of the nursing home and the staff. None of the 8 nursing home
cases was isolated in a side room for cohort care.
Outbreak Control
At the nursing home, the infection control nurse suspected norovirus based on clinical and epidemiological
features on November 15, six days after the index case in the nursing home had occurred. Hygienic measures
for controlling norovirus in institutional settings were implemented without waiting for virological
confirmation. Further 2 cases among the nursing home residents occurred within 2 days after the measures have
been applied.
At the hospital, the responsible health authorities decided to test cases’ stool samples for norovirus on
November 17, after a total of 16 cases have occurred within 7 days. As soon as laboratory results confirmed
norovirus infection (November 18), the infection control practitioner of the hospital began to implement
specific control measures such as enforced hygiene for the personnel and appropriate environmental
decontamination On November 21 these control measures were in place at the department. Thereafter, another
2 persons of the Department staff (on Nov. 23, 26) and another 2 subjects of the hospital patients (on Nov. 26,
28) fell ill with symptoms compatible with norovirus infection.
Discussion
Norovirus is easily spread from person to person by faecal-oral route and via aerosols. The virus is able to
survive in the environment for many days which allows producing a continuous source of infection (14, 22, 30,
31). The infectious dose is thought to be very low. The risk of being infected in a susceptible individual
following an infectious contact has been estimated to be at 21% (risk of transmission) (32). Large numbers of
people congregating provide an ideal environment for the rapid spread of this disease (33). Healthcare settings
tend to be particularly affected by outbreaks of norovirus. Hospital patients and nursing home residents
represent high-risk populations for the transmission of gastrointestinal illness. The residents are likely to be
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