A Filipino domestic helper is in critical condition with human swine flu, the Centre for Health Protection announced today.

It was the second serious case of the virus in Hong Kong.

Centre Controller Dr Thomas Tsang said today the maid, 37, needs mechanical ventilation to support her breathing while being treated at the intensive care unit at United Christian Hospital.

Her employers, a couple living in Kwun Tong, also had flu-like symptoms. As the wife is pregnant, she has been admitted to hospital for observation, while the husband was prescribed Tamiflu.

The patient developed a fever a day after arriving in Hong Kong from the Philippines on June 28 and was given medication at a private clinic. She returned for follow-up on July 1 when an X-ray showed her lungs were clear.

Her condition quickly deteriorated, though, and she was admitted to United Christian Hospital's intensive care unit with serious pneumonia symptoms on July 7.

Results of tests taken on July 7 and 8 showed she was negative for Influenza A. But one taken yesterday was positive for Influenza A, while further tests carried out at the centre's lab today confirmed she was infected with human swine flu.

Dr Tsang said they were investigating whether the maid had another hidden disease which could have led to her critical condition.

In the 24 hours up to 2.30pm today, 58 new cases of human swine flu were confirmed, involving 26 males and 32 females, aged between two and 55.

There have been 1,236 human swine flu cases in Hong Kong.