Ear, nose and throat surgeons say a loss of smell, as the virus causes swelling in the olfactory mucosa, could be used as a key clinical indicator in otherwise symptom-free carriers of COVID-19.

"It is these silent carriers who may remain undetected by current screening procedures, which may explain why the disease has progressed so rapidly in so many countries around the world," Flinders University professor and ENT specialist Simon Carney said.

"While further research is required, loss of smell, or anosmia, has been reported in as many as one in three patients in South Korea and in Germany, this figure was as high as one in two."

An ENT professor in London also reported a dramatic increase in patients with anosmia as their only symptom of COVID-19 infection.

Professor Carney said Australia was in a position to take advantage of these findings overseas to try and lower the rate of infection.

He said doctors and COVID-19 detection centres could use the subtle sign as part of their testing criteria and patients should also consider calling their GP if they notice this symptom.

Australian Associated Press