They ran smell tests on 2,956 volunteers with a history of COVID-19 infections and 569 who hadn't caught the virus. On average, the smell testing took place 671 days after participants had first been tested for COVID-19.

Of the COVID-19 group, 1,393 thought they had issues with smell, and tests confirmed about 80 percent of them did. Surprisingly, the other 1,563 people in that group didn't report any smell problems, but test results showed 66 percent of them had hyposmia or anosmia after their COVID-19 infections.

— Read more in Millions of Us Have Likely Lost Our Smell Without Even Realizing It at Science Alert.

Now surgeons at University College London Hospitals NHS Foundation Trust (UCLH) have cured a dozen patients, each of whom had suffered a profound loss of smell after a Covid infection. All had experienced the problem for more than two years and other treatments, such as smell training and corticosteroids, had failed.

— Read more in Patients with long Covid regain sense of smell and taste with pioneering surgery at The Guardian.

Now [Zara] Patel's team has tested a new treatment for long-term, COVID-19-related smell loss using injections of platelet-rich plasma derived from a patient's own blood. In a trial of 26 participants, those who received the treatment were 12.5 times more likely to improve than patients who received placebo injections. The study was published Dec. 12 in the International Forum of Allergy and Rhinology.

— Read more in Nasal injections could treat long-term COVID-19-related smell loss at Stanford Medicine.