In many cases the problem resolves itself in a matter of weeks. However, half the people who catch Covid may suffer long-term changes to their senses, according to preliminary studies.

Researchers at the Karolinska Institute in Stockholm ran tests on 100 people who had lost their sense of smell after a bout of Covid in March 2020 and found that, 18 months on, almost one in 20 had regained nothing whatsoever.

Previous research suggested a similar number were still suffering this deceptively unpleasant symptom six months after recovering from their initial illness. But the newly published findings indicate that, in a significant minority, it may endure even longer.