According to a study, published in the journal JAMA Otolaryngology – Head and Neck Surgery, one in ten people who lose their sense of taste and smell with the coronavirus may not get it back within a month.
Research on a small group of Italians who endured mild bouts of the disease found some still struggled to smell or taste a month after their illness.
The researchers surveyed 187 Italians who had the virus but who were not ill enough to be admitted to hospital.
Researchers asked them to rate their sense of smell or taste soon after they were diagnosed and again a month later.
Sixty per cent (113) reported an alteration in their sense of smell and/or taste.
Of those, 55 said they had recovered fully, 46 reported improvements in their symptoms and 12 found their symptoms were unchanged or worse.
Therefore, just half had fully regained their sense of taste and smell a month into their recovery.
A further 40 per cent had seen improvements and 10 per cent had not.
People who had severe symptoms found they took longer to get better, Dr Paolo Boscolo-Rizzo, of the University of Padova, and colleagues found.
They wrote in their paper: ‘Given the high incidence of Covid-19 infection globally, this is likely to result in a considerable number of patients with long-term dysfunction and its associated morbidity.’
The NHS listed altered sense of smell or taste as one of the key signs of Covid-19, along with a high temperature and persistent cough, back in mid-May after overwhelming pressure from doctors to do so.
Dr Claire Hopkins, one of the researchers and president of the British Rhinological Society, said her team are researching if altered taste and smell related to the coronavirus is long-lasting.
She told the BBC: ‘Data from other viral illnesses, and some of the new data we are gathering, suggest the vast majority of people will get better but for some, recovery will be slow.
‘For people who recover more quickly it is likely the virus has only affected the cells lining their nose.
‘For people who recover more slowly it may be that the virus has affected the nerves involved in smell, too. It can take longer for these nerve cells to repair and regenerate.’