Almost all cases of such transmission have occurred in China, but there have also been a handful of cases in Vietnam, Germany and Japan.
Almost all cases of such transmission have occurred in China, but there have also been a handful of cases in Vietnam, Germany and Japan.
"Globally, there have been only a few scattered, individual cases of onward, secondary transmission," said Morrison. "The risk remains very low to the United States and other advanced economies."
But that situation could be different in other parts of the world.
"If export occurs to countries in Africa and elsewhere where there are limited health security capacities, grave secondary outbreaks could emerge outside of China," Morrison added.
What are the symptoms?
Chinese scientists reported in The Lancet Friday that, based on a study of 41 early-detected cases, some of the new virus's symptoms resemble those of SARS.
All patients had pneumonia, most had a fever, three-quarters of them were coughing and more than half had trouble breathing.
There are, however, some "important differences," said lead author Bin Lao.
Identifying coronavirus symptoms is all the more important - and difficult - because of a simultaneous epidemic of seasonal flu, which has similar symptoms.
Incubation period
On Monday, the WHO estimated an incubation period of two to ten days. Among 34 patients examined by researchers from the Netherlands, the average period was 5.8 days.
For a 27-year-old man in Vietnam infected by his father, who had been in Wuhan, symptoms appeared after only three days, according to a letter published in the New England Journal of Medicine.
As a precaution, health authorities in France and other countries have set an isolation period of 14 days for repatriated nationals and other people coming from the coronavirus hot zone.
Avoiding infection
Health authorities and scientists say the standard precautions against viral illnesses are applicable: wash your hands frequently, cover up your coughs, try not to touch your face.
Anyone who does come down with the virus should be placed in isolation.
"Considering that substantial numbers of patients with SARS and MERS were infected in health-care settings", precautions need to be taken to prevent that happening again, the Chinese team warned in The Lancet.
"Globally, there have been only a few scattered, individual cases of onward, secondary transmission," said Morrison. "The risk remains very low to the United States and other advanced economies."
But that situation could be different in other parts of the world.
"If export occurs to countries in Africa and elsewhere where there are limited health security capacities, grave secondary outbreaks could emerge outside of China," Morrison added.
What are the symptoms?
Chinese scientists reported in The Lancet Friday that, based on a study of 41 early-detected cases, some of the new virus's symptoms resemble those of SARS.
All patients had pneumonia, most had a fever, three-quarters of them were coughing and more than half had trouble breathing.
There are, however, some "important differences," said lead author Bin Lao.
Identifying coronavirus symptoms is all the more important - and difficult - because of a simultaneous epidemic of seasonal flu, which has similar symptoms.
Incubation period
On Monday, the WHO estimated an incubation period of two to ten days. Among 34 patients examined by researchers from the Netherlands, the average period was 5.8 days.
For a 27-year-old man in Vietnam infected by his father, who had been in Wuhan, symptoms appeared after only three days, according to a letter published in the New England Journal of Medicine.
As a precaution, health authorities in France and other countries have set an isolation period of 14 days for repatriated nationals and other people coming from the coronavirus hot zone.
Avoiding infection
Health authorities and scientists say the standard precautions against viral illnesses are applicable: wash your hands frequently, cover up your coughs, try not to touch your face.
Anyone who does come down with the virus should be placed in isolation.
"Considering that substantial numbers of patients with SARS and MERS were infected in health-care settings", precautions need to be taken to prevent that happening again, the Chinese team warned in The Lancet.