The health district has received 25 notifications of flu this year, most of them in the past few weeks.

But the notifications do not reflect the prevalence of flu in the health district that is encouraging preventative measures including vaccination.

"The local health district is only informed of people who have been tested for influenza," its spokesman said this week.

"There would be an under-reporting of the flu due to people not visiting their GP or being tested.

"The Public Health Unit are not concerned about the notifications so far and we will continue to monitor and observe for any clusters or outbreaks.

"There has not been any aged care facilities reporting a flu outbreak so far this year."

The spokesman said the flu season officially started when there was a "significant increase in the number of influenza notifications".

"This is determined at a state level," he said.

"However, now is the time to start preparing for the influenza season as we have begun observing notifications in the Western NSW Local Health District."

The health district is encouraging Western NSW residents to avail themselves of the flu vaccine.

"Vaccination against influenza is an important way to protect yourself against the flu," its spokesman said.

"If people are already unwell it is important to stay home, or isolated as best as possible, to prevent spreading it to others, especially to vulnerable populations such as the very young, elderly and those with health conditions."

NSW Health reports flu is spread by viruses floating in tiny droplets from "a sick person's cough or sneeze".

Flu symptoms can include fever, chills, cough, sore throat, tiredness and muscle aches, and sometimes vomiting and diarrhoea.

Severe cases of flu can result in breathing difficulty and pneumonia. More than 2500 Australians die each year from complications caused by influenza, according to healthdirect Australia.

More information about flu can be found at www.health.nsw.gov.au.