[Norovirus gastroenteritis outbreak by person-to-person transmission in a nursing home].

BACKGROUND AND OBJECTIVE

The aim of this study was to conduct an investigation into an outbreak of gastroenteritis among health workers and residents (with different grades of dependence) at a nursing home.

PATIENTS AND METHOD

We detected an outbreak of gastroenteritis in a group of 52 health workers and 124 residents at a nursing home in Oliana, Lleida (Spain). A bidirectional prospective and retrospective cohort study was conducted into the consumption of water, food, grade of dependence (high, medium and low), and specific job. We studied the water supply and six food items. Faecal specimens from 30 patients were cultured and examined for Norovirus by polymerase chain reaction-reverse transcription. The possible implication of different factors associated with gastroenteritis was assessed by relative risk (RR) at 95% confidence intervals (CI).

RESULTS

We interviewed 97% of the patients (172/176). The overall attack rate was 53.3% (92/172). The symptoms were: diarrhoea 68.5% (63/92), vomiting 64.1% (59/92), nausea 63.0% (58/92), fever 33.7% (31/92), abdominal pain 28.3% (26/92), and headache 14.1% (13/92). The epidemic curve highlighted transmission for 19 days. The risk factors associated with gastroenteritis were high (RR = 1.6; 95% CI, 1.0-2.6) and medium (RR = 2.8; 95% CI, 1.0-8.0) levels of dependence, health worker with high level of contact with residents (RR = 2.8; 95% CI, 1.1-7.3) and those doing cleaning work (RR = 2.8; 95% CI, 1.0-8.0). Bacterial cultures were negative for samples of food and water. Also, cultures were negative for bacteria in faecal samples but tests were positive for Norovirus in 12 faecal samples.

CONCLUSIONS

We showed a Norovirus outbreak in a nursing home, person-to-person spread, associated to high and medium grades of dependence among residents, health worker with high level of contact with them and with those doing cleaning work.