GENEVA (REUTERS) - The coronavirus outbreak is "getting bigger", the World Health Organisation (WHO) said on Friday (Feb 28) after Nigeria confirmed sub-Saharan Africa's first case, reiterating its warning that the virus could reach most "if not all countries".

Five more countries have reported their first case of the Covid-19 virus, all with travel history connected to Italy - Nigeria, Estonia, Denmark, Netherlands and Lithuania - WHO spokesman Christian Lindmeier said.

"The outbreak is getting bigger," Mr Lindmeier told a Geneva news briefing.

"The scenario of the coronavirus reaching multiple countries, if not all countries around the world, is something we have been looking at and warning against since quite a while," he said.

China has reported nearly 80,000 cases in the two months since the outbreak began in Wuhan in Hubei province, he said.

About 10 per cent are classified as severe, with 2,791 deaths so far, according to the WHO's latest figures.

Forty-nine countries outside of China have reported 4,351 cases and 67 associated deaths.

Mr Lindmeier said the WHO was looking very carefully into reports of some people getting re-infected.

"We need to carefully look at how the tests were taken, how the person was examined, if it was maybe overlooked that the person still had the virus somewhere in the residue in the body, whether they got reinfected by different means or ways," he said.

"We're not in a position to say it is possible or not to be coming back and being re-infected.

"In general, we would expect that a person who had the coronavirus infection would be immune for at least a while afterwards. But again this is something we do not yet know."

A WHO mission to Iran - which has now reported 388 cases and 34 deaths - is supposed to start work early next week, and is still being put together, he said.