Objectives:
The presented study is aimed at determining the subjective psychological reaction to the outbreak of pandemic in healthcare workers and is part of a wider research project covering successive waves of increasing number of SARS-CoV-2 infections during the COVID-19 pandemic in Poland.

Methods:
664 respondents completed the anonymous online questionnaire in the period from March 12, 2020 to May 3, 2020. This is the period of the first lockdown in Poland. Data were collected using the snowball method (employees passed the questionnaire over the Internet to subsequent groups of employees in subsequent healthcare units).

Results:
The outbreak of pandemic had varying impact on the well-being of 96.7% of respondents. Subjectively perceived stress of varying intensity was reported by 97.3% of them, low mood was reported in 19.0%, and anxiety in 14.1% of the respondents. These results and other features of the psychological reaction (including sleep problems) to overload in healthcare workers may indicate mental deterioration in the first weeks of pandemic.

Conclusions:
The results obtained in the study group may encourage further analyzes of healthcare workers’ mental state and contribute to discussion on the COVID-19 pandemic.