In late April, the World Health Organisation (WHO) raised the level of pandemic alert to Phase 5 in response to the outbreaks of the new Influenza A (H1N1) virus, or "human swine flu", in some countries. Health authorities in Hong Kong were swift to react and quarantine measures were imposed at a Wan Chai hotel following the confirmation of the first human swine flu case in Hong Kong on May 1 involving a hotel guest. All the hotel guests were released on May 8.