A Chinese woman infected with the new coronavirus showed a dramatic improvement after she was treated with a cocktail of anti-virals used to treat flu and HIV, Thailand's health ministry said on Sunday.

But as markets opened in China on Monday morning some majors shares fell by the maximum daily limit as the country's investors got their first chance in more than a week to react to the spiralling coronavirus outbreak.

The benchmark Shanghai Composite Index dived 8.73 percent and the Shenzhen Composite Index sank 8.99 per cent.

The scale of the plunge was remarkable even by the standards of China's notoriously volatile share markets, indicating deep concern over the viral outbreak's economic impact. The yuan also weakened by nearly 1.5 per cent to around 7.00 to the dollar.

In Thailand, the 71-year-old patient tested negative for the virus 48 hours after doctors administered the combination, doctor Kriengsak Attipornwanich said during the ministry's press briefing.

"The lab result of positive on the coronavirus turned negative in 48 hours," Kriengsak said.

"From being exhausted before, she could sit up in bed 12 hours later."

The doctors combined the anti-flu drug oseltamivir with lopinavir and ritonavir, anti-virals used to treat HIV, Kriengsak said, adding the ministry was awaiting research results to prove the findings.