The World Health Organisation (WHO) has recorded 65 cases of the coronavirus among staff based at its headquarters, including at least one cluster of infections, an internal email obtained by The Associated Press shows, despite the agency's public assertions that there has been no transmission at the Geneva site.

The revelation comes amid a surge of cases in Europe, host country Switzerland, and the city of Geneva, in particular, and the email said about half of the infections were in people who had been working from home.

But 32 were in staff who had been working on premises at the headquarters building, indicating that the health agency's strict hygiene, screening and other prevention measures were not sufficient to spare it from the pandemic.

Farah Dakhlallah, a WHO spokeswoman, confirmed the accuracy of the information about the case count in an email to the AP, but said the UN health agency had not yet determined whether the Covid-19 spread happened at its offices.