Deaths trigger mushroom alert

The toxin in death cap mushroom (amanita phalloides) stops human cells dividing, affecting organs such as the liver. Photo / Supplied

Urgent new warnings about Canberra's lethal death cap mushrooms have been issued in the wake of two deaths after a New Year's Eve feast.

A 52-year-old woman and a 38-year-old man died after being flown to Sydney's Royal Prince Alfred Hospital.

Another remains in hospital. A fourth diner was released after treatment at Canberra Hospital.

The deaths bring to five the number of victims killed by the imported mushroom species in Canberra over the past decade, with at least a further dozen known to have survived.

The mushrooms, which thrive near oaks and other introduced trees, hold enough poison to kill an adult, with the toxin spread throughout all its parts and unaffected by peeling or cooking.

"All parts of this mushroom are poisonous, and eating just one mushroom can be fatal," Canberra Hospital emergency department director Dr Michael Hall said.

The poison attacks the liver - at times requiring a transplant - and unless victims can get to hospital fast enough for doctors to flush the toxin out and attack it with drugs, they can die from liver failure.

Death caps are an annual threat to the nation's capital, usually in warm, wet autumns but thriving now because of heavy summer rains.

Signs are posted throughout Canberra warning against collecting wild mushrooms because death caps, which have white gills, are similar in appearance to edible Chinese varieties.

"People should not eat any mushroom unless they can be absolutely certain that it is not poisonous," Hall said.