Confirmed cases of a mystery virus causing atypical pneumonia have continued to grow as authorities in the central Chinese city of Wuhan ruled out Severe Acute Respiratory Syndrome, or SARS.
In Hong Kong, 21 people have been treated in isolation in hospitals in the city after arriving there from Wuhan, the Hospital Authority said, adding that none of the patients had visited Wuhan's South China Seafood Market mentioned as a possible link between cases by mainland Chinese health officials.
"The patients concerned had not visited wet markets in Wuhan before the onset of symptoms," Hospital Authority (HA) infection control chief Raymond Lai said in a statement.
"The HA will keep monitoring the patients' conditions and provide appropriate treatment," Lai said.
Seven of the 21 have been discharged, while the rest are in a stable condition and being treated for fever, respiratory symptoms or pneumonia, the statement said.
But the Hong Kong Centre for Health Protection (CHP) has raised its response level to "serious," saying the unknown pathogen had "public health significance."
Health officials in Wuhan said on Sunday that seven people are seriously ill in the city with the mystery virus out of a total of 59 cases since the outbreak began.
"The public is urged to maintain strict personal, food and environmental hygiene both locally and during travel," China's National Health Commission said in a directive sent to the Hong Kong government and quoted on its website.
No fatal cases reported
It said no fatal cases have yet been reported, and a total of 163 close contacts were under medical surveillance and symptom-free so far.
"For the time being ... the investigation has not identified any evidence of definite human-to-human transmission and no healthcare workers have been infected," the Hong Kong CHP said.
Hong Kong experts have said in recent media interviews that the possibility of person-to-person transmission can't be ruled out, however.
The type of virus causing the outbreak is "still under investigation," according to China.
"Respiratory pathogens including influenza viruses, avian influenza viruses, adenovirus, Severe Acute Respiratory Syndrome and Middle East Respiratory Syndrome have been ruled out," the CHP statement said, citing the Chinese health ministry.
The Hong Kong CHP also warned people to take personal hygiene precautions and stay away from live animal markets.
But Ai Li, a resident of Wuhan, said there wasn't much public health advice or reporting on the outbreak across the border in mainland China.
"I have seen news about it online, but we haven't heard anything [from official media reports]," Ai said.
Asked if people were wearing masks or taking other precautions in Wuhan, she said: "No, nobody is worried. Nobody is even thinking of panicking."
China's official tendency to silence
A mainland Chinese resident who gave an online nickname Zhuzhu said there is a world of difference between the public information culture in Hong Kong and the official tendency to silence under the ruling Chinese Communist Party.
"Hong Kong has done a good job in this matter, and they have done a good job of preventive measures," Zhuzhu said. "Here in China, preventive measures aren't carried out very well."
The World Health Organization (WHO) said on Sunday that there could be a link to animals.
"The reported link to a wholesale fish and live animal market could indicate an exposure link to animals," the WHO said, adding that the symptoms reported in patients were mainly fever, with a few patients having difficulty in breathing and chest radiographs showing invasive lesions on both lungs.
"The symptoms reported among the patients are common to several respiratory diseases, and pneumonia is common in the winter season," said the WHO, adding that the concentration of cases should be handled "prudently".
But it said it was against imposing any travel or trade restrictions on China.
SARS -- described as atypical pneumonia caused by a coronavirus -- killed 349 people in mainland China and another 299 in Hong Kong in 2003. The virus, which infected more than 8,000 people around the world, is believed to have originated in the southern Chinese province of Guangdong.
The WHO declared China free of the SARS virus in May 2004, although it criticized the Chinese government's initial attempt to cover up the crisis.
Reported by Qiao Long and Wong Lok-to for RFA's Mandarin and Cantonese Services. Translated and edited by Luisetta Mudie.