“The committee is aware of very recent cases of coronavirus who are at the time of diagnosis asymptomatic or minimally symptomatic,” he said.
“We’re also aware of one fairly convincing case of probable transmission from a pre-symptomatic case to other people two days prior to the onset of symptoms.”
That case was a Chinese national who travelled to Germany to talk at a conference and was apparently not displaying symptoms at the time, but developed them one or two days later. Since then, four people who were at that seminar have contracted the virus.
Professor Murphy stressed the information about that case was “very limited and preliminary”, and all the evidence from China suggested almost all of the cases were only infectious when patients were symptomatic. However, the committee wanted to take a “highly precautionary approach”.
That precautionary approach now means people who have been in the Hubei province of China must be isolated in their home for 14 days after returning even if they do not have symptoms.
“Given the substantially lower number of cases in China reported outside of Hubei province, we do not currently recommend self-isolation for travellers from other parts of China or from other countries,” Professor Murphy said.
“We are however closely monitoring the development of cases outside of the Hubei province and will update this advice if necessary.”
It follows the announcement earlier on Wednesday that any Australians evacuated from Hubei would be quarantined on Christmas Island for 14 days. Health Minister Greg Hunt said that decision was made “on the basis of the medical advice”.
Six cases in Australia
The new diagnosis takes the total of coronavirus cases in Australia to six. The man, aged in his 60s, tested positive on Wednesday morning. He is in isolation after going to the Monash Medical Centre with respiratory problems. The man was recently in Wuhan, and became unwell more then two days after returning to Melbourne.
Members of the man’s family were traveling in public places since the man returned from China, but have been quarantined since his positive test.
Victoria’s chief medical officer Dr Brett Sutton said there are 14 pending results of people suspected of having the illness. A total of 61 negative tests have been returned.
In NSW the number of patients awaiting test results has also increased, with 16 ranging in age from two to 66 waiting to see whether or not they have the virus. More than 40 people in the state have been tested for the virus so far.
“The fact that we have 16 cases under investigation just reflects that we have broadened our testing,” the state’s chief health office Dr Kerry Chant said.
She said the cases had been less severe than those in China, where the virus has now killed more than 130 people, with two of the four NSW patients now significantly improved.
However, she said it was important for people who had been in Hubei province who experienced any symptoms – no matter how mild – to be tested.
“Even if you have that bit of runny nose, you are feeling just unwell, please come forward because we want to one, both detect those cases but also it will help us in our understanding [of the virus],” she said.
ANU Medical School Professor Peter Collignon, an expert in infectious diseases, said it was likely that most of the thousands of people with the coronavirus caught it from someone who had symptoms.
Professor Collignon said the expanding number of infections meant that the mortality rate was lower than initially feared, but that even a low mortality rate would have serious consequences if the virus spread rapidly.
“If you infect a million people, you would still have a lot of people very sick and a lot of people who die,” he said.
With Dana McCauley
Rachel Clun is a journalist at The Sydney Morning Herald.
Paul is a reporter for The Age.