The man, who was a patient in the Nepean Hospital Intensive Care Unit died on Monday, and had tested positive to the H1N1 influenza.

The state's chief health officer, Dr Kerry Chant said the man had underlying medical conditions, making him more susceptible to the virus.

"We are waiting on formal findings from the coroner to determine the degree to which H1N1 may have contributed to the death," she said.

"The details of the man's death can be released now that his family has been notified of the initial findings and counsellors have offered them assistance."

People with breathing difficulties, underlying medical conditions, pregnant women and Aboriginal people who develop flu-like symptoms should seek medical assistance, Dr Chant said.

People with symptoms of the flu should also get medical assistance if their condition goes downhill.

In the Sydney West Area Health Service catchment area, 337 people are confirmed with the virus.