Jahresbericht - Gesundheitsserver - Land Steiermark

immunocompromised and to experience a more complicated clinical course of norovirus infection (34-39). In
nursing homes faecal incontinence and reduced mental function may also present challenges to outbreak
control. Zoonosis directives require investigation of foodborn outbreaks. Norovirus accounts for 50% of
foodborn outbreaks.
We describe a norovirus outbreak comprised 43 cases in a nursing home and at a hospital department. The
outbreak investigation revealed that contaminated food or staff members of the nursing home kitchen could not
be suggested to have introduced the virus into the nursing home environment. Instead, a visitor of the index case
reported about projectile vomiting and diarrhoea having occurred the day before she had visited the index case.
The virus was probably introduced to the nursing home by this community case of norovirus infection. The
increased number of consultations with general practitioners and the increase in absences from school due to
short-living gastroenteritis in the months October till December compared to the previous months indicated an
increased activity of norovirus in the community of the particular health district.
In the nursing home, the epidemic curve suggested a common source of infection at the beginning of the cluster.
Contaminated food was not implicated in the point source spread whereas vomitus of the index case was
suggested to have been the point source of infection. Projectile vomiting of the index case occurred while most
residents and staff members were together in the dining room. In 16 of 24 nursing home cases (index case
exclusive), the median time between exposure to that vomiting episode and illness suggested direct airborn
transmission via aerolized viral particles which were generated during vomiting of the index case, and
subsequently ingested by those present in the dining room during the vomiting episode. For the remaining 8
cases, the virus must have been spread by direct person-to-person transmission or indirectly by contacts with
contaminated environment. Subsequently, the virus was introduced into the Internal Medicine Department by
transfer of 8 cases of the nursing home residents. The nursing home cases had probably contact with other
hospital patients as they were primarily not isolated, although patients with symptoms suggestive of NV
infection referred to hospital, should be admitted directly to a side room until an alternative cause of vomiting is
established (22).
The epidemic curve indicates that the hospital outbreak was propagated among the department staff and the
hospital patients by direct person-to-person transmission or exposure to contaminated environment. Specific
hygienic measures for preventing transmission of norovirus from infected patients to staff members and for
preventing spread of virus to unaffected patients at department level were not considered within the first 7 days
of the department outbreak. Norovirus outbreaks can be diagnosed presumptively on characteristic clinical and
epidemiological features (24). When norovirus is suspected, the most effective way to respond to and to rapidly
control the outbreak by means of preventing further cases is to immediately institute hygiene measures
including enforced hand-hygiene and effective environmental decontamination without waiting for virological
confirmation (22). In the described outbreak, norovirus was suspected too late, hence the specific measures for
controlling norovirus were belatedly set. In the nursing home, 6 days after the index case had occurred, the
infection control nurse suspected - based on clinical and epidemiological features - norovirus as causative
pathogen before the results of the stool tests were available. She implemented specific measures including
mainly appropriate hand-hygiene and effective environmental decontamination. Whether these measures had a
terminating impact on the course of the outbreak or the outbreak was self-limiting as 15 of 23 residents have
already been fallen ill at the time when the measures were set, remains unanswered. In the hospital, the control
measures were implemented only after virological confirmation, at this point in time, when a total of 16 cases of
gastroenteritis have already occurred at the department within 7 days. But norovirus should be promptly
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