Thread by @MarionKoopmans

Wow factor paper of the week: biorxiv.org/content/10.110…
Loss of taste and smell is a key symptom of COVID-19. This group studied infection of olfactory bulb sensory neural cells from nasal mucosal brush samples of 5 patients with anosmia.

They found virus proteins (by immunostaining) in 3 of them. Then they went ahead and infected hamsters.

They found evidence of infection in mature and immature olfactory sensory neurons, and found different parts of the brain by PCR positive but not by immunofluorscence. Functional loss was tested in a very cool way- read the paper to find out.

Using RNA seq, they found differentially expressed genes associated with innate immune response, acquired immune response and chemokine signalling (say: what we expect), but also signs of neuroinflammatory responses, and astrocyte and microglial activation.

Then they went back to 4 patients, now looking at patients in which the anosmia persisted for months. These also had other neurological signs / symptoms, which is why they were seen at the hospital (none of them had severe disease in the acute phase)

All patients had PCR positive brush samples, not regular samples, 3 of the 4 were positive for virus antigen, and all had upregulated IL6, to similar levels as in acute cases. So persistent infection of olfactory cells.

Incredibly important paper, raising questions on 1) diagnostics in persons with delayed recovery 2) neurological impact and 3) possibility of persistence. Number is small and biased, but certainly will flag this he physician in charge of our post COVID clinic @DebbyvanRiel