Health officer issues asthma warning ahead of Victoria thunderstorms

Victoria's chief health officer has advised asthma sufferers to remain vigilant with thunderstorms forecast to hit the state's east.

The warning from Professor Charles Guest comes nine days after Melbourne was struck by an unprecedented thunderstorm asthma event that has so far resulted in the deaths of eight people.

The chief health officer has advised asthma sufferers to keep their medication close at hand with storms predicted for Gippsland and the state's northeast in the afternoon.

"Thunderstorms, combined with pollen in the air, can cause an increase in asthma symptoms, hay fever and breathing difficulties," Prof Guest said in a statement.

READ MORE: Death toll rises to eight after Melbourne 'thunderstorm asthma' outbreak

Last week more than 8500 patients were treated for breathing difficulties on Monday and Tuesday.

The storm event saw a high pollen count and thunderstorm conditions combine to produce tiny particles in the air that penetrated deep into people's airways, causing attacks for asthma sufferers.

The Inspector-General for Emergency Management has announced an investigation into the cause of the eight deaths.