Disease experts on Tuesday questioned a statement by the World Health Organisation (WHO) that transmission of Covid-19 by people with no symptoms is "very rare", saying this guidance could pose problems for governments as they seek to lift lockdowns.

Maria van Kerkhove, an epidemiologist and the WHO's technical lead on the coronavirus pandemic, said on Monday that many countries undertaking contact tracing had identified asymptomatic cases, but were not finding they caused further spread of the virus. "It is very rare," she said.