Uncommon for coronavirus to spread before infected person shows symptoms
There is evidence that the new coronavirus can be spread before the infected person shows any symptoms.
This, however, is uncommon, said Health Minister Gan Kim Yong as he spelt out what is known so far about the virus in Parliament yesterday.
He said this form of transmission has so far involved isolated cases only. At this point, the evidence still points towards higher transmissibility when the person is displaying symptoms - which is generally the case with coronaviruses.
Those who are exposed to the virus may be well for a few days before developing symptoms such as a fever or cough. Some may also develop pneumonia.
The virus was first reported in the city of Wuhan, China, on New Year's Eve.
Current evidence suggests that the virus transmission is mostly via droplets.
"What this means is that the virus is carried within droplets emitted from an infected person over a short distance, such as when the person coughs or sneezes," said Mr Gan in a ministerial statement.
"If these droplets come into contact with the eyes, nose or mouth of an individual, directly or indirectly through hands that have come into contact with these droplets, the individual may become infected."
However, potential infection from asymptomatic people is less likely to be from coughing or sneezing directly, but "more likely by touching contaminated surfaces, for which masks offer no protection", he said.
Contact transmission can happen when a person sneezes or coughs, and the droplets fall onto the surfaces of tables and chairs, for example, where the virus may remain active "most likely two to three days" although this is not certain yet, said Mr Gan.
When someone touches the surfaces, the virus can be transferred to his hand and if he then rubs his eyes or nose without washing his hands, he may become infected.
"This is also why we only quarantine the close contacts of confirmed cases. For more transient contacts, such as individuals that the confirmed cases may have walked past in malls or hotels, the risk of transmission is low."
A key reason some people have started to mask up is the fear of breathing in the virus in public. Mr Gan said there is no evidence currently to suggest that the virus is airborne.
"There are other viruses, such as chickenpox, which can easily be transported via air currents... The novel coronavirus is not in this category of viruses," explained Mr Gan.