Gabriel Leung, dean of HKU's medical school on #CoronavirusOutbreak: basic reproductive number - secondary cases generated by an index infected case - is 2.13. According to best estimate, case count doubles every six days, in the absence of any public health intervention. 
Inferred number of cases is around 25k, while inferred number of infections, i.e. including those who are in incubation stage, is near 44k.
Epidemic curves with or without population quarantine are very similar, so the policy may not have a substantial impact on the course of outcome. In other major Chinese cities, the outbreak will reach its peak in April/May, and die down in June/July, says Leung.
Chongqing is expected to have the largest epidemic, as it has a large population and the most intense traffic volume/coupled tightly with Wuhan, among five city clusters. Expected to peak 1~2 weeks before other cities, such as Beijing, Shanghai and Guangzhou.
If prediction is correct, expected to see epicentres of self-sustaining epidemic in other major city clusters.
Besides exported cases from Wuhan, exported seeds will likely start a local epidemic. "Question is can this be contained within mainland China?" says Leung
Besides exported cases from Wuhan, exported seeds will likely start a local epidemic. "Question is can this be contained within mainland China?" says Leung
Given Beijing, Shanghai, Guangzhou and Shenzhen city clusters accounted for 53% for international travel, if and when they develop epidemic, they will in turn and seed other major ports as destinations, he adds.
He also notes that this is a pessimistic prediction, as it's drawn based on the assumption there's no public health intervention. "As a precautionary principle, we have to be prepared the epidemic may become global...There is a not-insubstantial probability this might happen."
"To change the course of epidemic curves, we are looking at substantial draconian measures limiting population mobility, that should be taken sooner rather than later," including cancellation of mass gathering, schools, flexible work arrangements.
On question about border control, Leung says the government must do more. Question is how to sustain #HongKong’s food supply, increase capacity to deal with major epidemic if logistic chains are interrupted and make sure it’s feasible, implementable and enforceable.
Critical knowledge gap now is the viral load. If viral shedding scales with symptoms - more symptoms more infective - and exponentially, "it would mean those who show mild symptoms are much less infective. But that is a conclusion we can only hope for but with no evidence of."
"Be honest to your doctor," says Leung. This is to help, not just yourself, but also the rest of the society. The report has been submitted to #HongKong government, with suggestions to take more infection control measures.
Pathogens tend to spread more by airborne route rather than large droplets, which surgical masks cannot prevent. But it's not practical to wear N95 for long hours. General advice is still wear a mask when you go out of your home. Avoid unnecessary travelling.
There is no system to trace where all visitors have been in the last 14 days and no existing mechanism to verify if visitors are being truthful in health declaration forms. There is limitation, Leung admits, repeating calls that govt should do more.
