WASHINGTON (REUTERS) - Robert Redfield, director of the US Centres for Disease Control and Prevention (CDC), told the US Congress on Thursday (Feb 27) that his agency is aggressively evaluating how long coronavirus can survive and be infectious on surfaces.

"On copper and steel it's pretty typical, it's pretty much about 2 hours," Redfield said at a House of Representatives hearing on the government response to the fast-spreading virus.

"But I will say on other surfaces - cardboard or plastic - it's longer, and so we are looking at this."

He said infections contracted from surfaces rather than through the air could have contributed to the outbreak on the Diamond Princess cruise ship.

Still, Redfield said he did not think surface transmission would impact cargo shipments.

He also said the mortality of the virus could be lower outside of China.

"We don't have the data, but I at least suspect if you look at the mortality rate of this disease outside of China, we're probably looking right now at somewhere around half a percent, but again, we'll have to see more data to really be clear on that."

The World Health Organisation (WHO) has suggested the mortality rate in China is between 2 and 4 per cent. Seasonal flu has a mortality rate of about 0.1 per cent, Redfield said.

The virus has so far mainly battered China, causing nearly 80,000 infections and more than 2,700 deaths, according to WHO figures. It has spread to 46 other countries, where around 3,700 cases and 57 deaths.