The Centre for Health Protection on Tuesday said two children were in intensive care after going down with severe flu. It said both have underlying illnesses and neither had travelled or received the seasonal flu vaccination.

The first case involves an 11-year-old boy who developed a fever, a cough and a shortness of breath on Saturday. The following day, he was admitted to Princess Margaret Hospital, before being transferred to the hospital's paediatric intensive care unit with low blood pressure on Tuesday.

Doctors say he has influenza A, complicated by shock and that there had been a flu-like outbreak at his school dormitory. His condition is serious.

The second case involves an 11-month-old boy who was in Kwong Wah Hospital due to an underlying disease.

On Monday, he developed a fever and a cough and was taken to intensive care, where he is in critical condition. He has now been diagnosed with influenza A, complicated by severe pneumonia. One of his household contacts recently had respiratory symptoms.

There have now been 16 severe paediatric flu cases since the start of the school year, including one that was fatal.