A group of surgeons has urged doctors to pay special attention to signs of 'smell blindness', which affects many Covid-19 patients.

Two-thirds of the patients infected with the new coronavirus experience this specific condition, said Prof Dr Saowarot Phattharaphakdi, chairwoman of the Royal College of Otolaryngologists (Head and Neck Surgeons) of Thailand.

More and more studies have found a link between Covid-19 infections and anosmia - smell blindness, or losing the ability to detect certain smells.

Anosmia was found to be more common in patients with mild symptoms of Covid-19, she said, adding that the rate of anosmia in this group is as high as 30%.

The college is urging doctors to look for loss of taste and smell in the patients they treat.

The first known Covid-19 infected patient who also experienced anosmia in Thailand was a person in Sakhon Nakhon who had returned from Phuket where she worked, said Prof Dr Saowarot.

Also, a 22-year-old woman in Prachin Buri who was recorded as the province's fifth Covid-19 case said she also temporarily lost her sense of smell.

She said she had dined out on March 21 with friends and two days later was surprised to find herself unable to smell anything or taste food.

She thought she had an allergy until March 26 when she learned that one of her friends had the virus.