Background:

In April 2018, an unusually high number of eye, throat and nose irritative symptoms, nonspecific gastrointestinal symptoms and dizziness were identified in workers in the microbiology (LAM) and clinical analysis (LCA) laboratories of a tertiary public hospital in Mallorca; these symptoms were also associated with perception of unusual odors.

Objective:

To confirm the presence of an outbreak, identify its causes, and contribute to its prevention and control.

Methods:

Epidemiological study of the outbreak involving qualitative and quantitative methods. The qualitative component was based on conducting focus groups The quantitative study allowed us to develop epidemic curves, based on employee visits to the hospital’s occupational health service (OHS) due to either symptoms or episodes of sickness absence (SA). Lastly, available industrial hygiene reports were reviewed to examine possible relationships with the distribution of cases.

Results:

Two operational case definitions were established through the focus groups, along with identification of possible explanations for the outbreak based on employee perception. The quantitative study confirmed the outbreak in the LAM, but not in the LCA. The SA episodes in the LAM between weeks 16 and 39 exceeded the number of expected cases four-fold. We also detected an excess of visits to the OHS during the same time period.

Conclusions:

The quantitative study confirmed an epidemic outbreak that has since ended, although the qualitative study indicated the persistence of bad smell and discomfort. The improvement of epidemiological surveillance systems as a result of the study will facilitate the monitoring and control of future possible outbreaks.

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